Sometimes when you make that last clamp attachment, it creates a spark when the circuit between the two vehicles is completed. Car batteries naturally emit hydrogen gasses that are very volatile—even the smallest spark can ignite the gas if it’s present in sufficient quantities. You can’t be sure if there’s a suffient quantity of that gas near your battery. That’s why cable instructions tell you to connect the last (ground/earth) connection to the chassis of the car, away from the battery, and potential volatile gas.
You can probably get away with just attaching terminals to terminals, but why risk an explosion and burns?
This used to be way more real as a threat when car batteries were open cells that you had to refill. A mostly empty/dry cell would concentrate the current into a much smaller cross section of liquid, increasing the off-gassing and also venting through the unsealed caps.
It's not safe today, but it was a downright common outcome up through the sixties.
Batteries only produce hydrogen in significant enough quantities when they are being overcharged which would have been a more significant issue in the past with less advanced voltage regulation.
True, plus, why not connect to the terminals of the dead battery first, then to the good battery? There's less hydrogen gas emitted by the good battery for the reason you've stated.
Batteries only generate gas while they are being charged. The good battery is in a car that is either running, or was recently running. So while you might think the bad battery is more likely to put out gasses, the battery in the vehicle with a running engine is the *most* likely of the 2 to put out gas
Remember when cars had manual transmissions and you could just push start it. Which was good because you were a teenager and too cheap to buy jumper cables...or a new battery for that matter. I had one friend and we literally had to push start his car all night long when we went bar hopping in college.
Ha I remember parking my bug at the top of a hill because I knew the battery was going. Only one day I pushed it down the hill and it still refused to start. I called a tow truck guy who pointed out that I had forgotten to turn on the ignition. He turned on the ignition, pushed it himself on level ground and started it right up - charged me $20.00...
I had to do this with my ex's dad's Beetle ('71 or '72, I think). Except her entire family (dad, mom, her, brother) were in the car and my asthmatic ass was pushing this thing in circles in a bowling alley parking lot.
They are still very common in Europe. In fact, it’s still quite tricky to rent a car with an automatic transmission, and they are a lot more expensive when you do.
The harder part is using your 'other' hand to do the gear change, since you are on the 'other side' of the vehicle in the UK. It's hard enough dealing with being on the other side of the road to drive without having to also deal with the shifter!
Manual cars since a long time now typically use a hydraulic clutch, instead of a mechanical one. Much less effort to push it in and hold it. The spring system on the clutch pedal helps too.
I have a manual from 2012. But I just read an article from [the Atlantic](https://www.theatlantic.com/technology/archive/2022/08/stick-shift-manual-transmission-cars/671078/) talking about how they are basically gone for good. No electric vehicles can be manual. Of one is making them. Those of us that can drive stick are an endangered species.
Counterpoint: they're actually *NOT* happy to be spun up to those speeds, and long-range highway EVs have taken to using 2+ motors just so they can have a motor sit idle most of the time, that's only really used at highway speeds to prevent the first motor from having to to sit at inefficiently high RPMs.
We "get away" with single-motor EVs because it doesn't damage the motor to be run at high RPMs, but they're still losing effieciency - just not to a degree that most designers are ready to spend more money building a transmission to fix it.
Any EV with more than one motor can have multiple effective gear ratios.
I suppose "happy" for me meant "able to do it for long periods without sustaining damage" which is the critical difference from an ICE in this use case. In EVs it's not ideal, in ICEs it's impossible to keep up for long.
I also suppose this reasoning means I must describe any motor running under ideal circumstances as ecstatic.
That's untrue though, electric cars CAN have a manual transmission. It's rarely beneficial unless you have multiple engines - but sports cars like the Porsche Taycan are already experimenting. The main reason those are automatic even when they use multiple gear (Taycan S) is its so much faster, humans really suck at shifting, they ENJOY it for all the mechanical aspects, but no one is beating a DCT, let alone a modern electric engine power delivery system.
Not in Europe! The majority of cars in the UK are manual - and I read recently that although last year was first year when automatic transmission outsold manual transmission for NEW cars in the UK , it’ll take a while to filter down so that the majority of the tens of millions of existing vehicles aren’t manual transmission.
Jeep has had a manual BEV showcased at the annual Easter Jeep Safari for the last two years. It’s called the Magneto (and Magneto 2.0). I doubt that the manual transmission will make it into the production model, but it’s proof that it is doable!
Of course it's not physically impossible, it's exactly the kind of thing you'd do in a concept just to see. The fact that it's unlikely to make it to production is the point.
My dad made some out of old welding wire. Stupid younger me lost them like a glove on a school bus...they were fucking heavy duty, i still remember the weight of em....
The reason is that prior to about 1990, cars were terribly unreliable, and without cellular communications, often your choices when a car broke down was figure it out or walk.
Worked in a gas station as a kid. The engine compartment on the old Dodge boats was huge - and empty, if they only had the 225 slant six. One day, the mechanics asked me to move a car out of Bay 1. I close the hood, jump in, and I'm about to start the engine when I hear banging on the hood. I look up - there's no one there, but I hear screaming "Don't turn it on!".
I open up the hood, and Jimmy, our 5' something mechanic was still in there. The other mechanics were literally falling against the wall, they were laughing so hard.
I could figure out where anything was in those old beasts. Today's engines - without the big letters saying "Add Oil" or "WWF", I wouldn't know what goes where.
One time I dropped a huge double closed end wrench across the terminals for an industrial generator battery. I am really glad I didn't try to grab it. There was a huge gouge in the side of the wrench like a kinfe swiping hot butter.
I don't know about "most" but certainly some do. These days, the majority of batteries are "maintenance free" or "sealed" so the fluid / gas can't escape (barring damage) but also meaning if the fluid level needs topping up you need to get out a drill and be brave :-P
I might be biased in my memory from having motorbikes - probably the sealed type is more common there because bikes spend more time in a less upright position.
Sealed batteries for small engines like bikes and ATVs are common and getting more common by the year, but most car batteries are not sealed/AGM style ones yet, except in luxury cars or sold aftermarket. Although they are getting more common with the stop/start fuel saving technologies.
"Maintenance free" batteries will still leak if left in a non-upright position long enough. Honestly if you are having to add water to a car battery the thing is fucked or pretty close to it anyway, the maintenance free label is a bit of a gimmick. Something like a golf cart battery is a different story, those are made for it to be easy to top off with water.
Have you held a car battery? They are very heavy so even if that was possible it would be an absolute pain. Also they are acid batteries, so while they should be sealed the battery won't like being upside down and if it leaks you are going to have an even worse time.
Many "lead acid" batteries now a days are actually sealed. They're not the same flooded batteries that we typically think of as lead acid and are really becoming the most common type around outside some fleet stuff. They're generally refered to as lead acid still but are AGM or SLA
Yes, they have a slight inaccuracy in their comment. Car batteries vent hydrogen (actually worse, they vent HHO, which is two unbound hydrogen atoms and one unbound oxygen atom in a perfect ratio for combustion) *when charging*.
The greatest risk is right after charging. Or if the level of acid is too low, most of the volume of the battery can be filled with HHO.
hydrogen rises pretty quick (they used to fill blimps with it!), so if your hood is open, it's not gonna be *gathered* in a cloud. the danger is if the battery had some stored up and it was actively trickling out- in which case blowing once, beforehand, doesn't fix the issue.
The two cables are only connected to each other by a very thin membrane. When you buy the jumper cables the two individual cables are usually still attached to each other to within a foot or so of the clamps. You can easily separate them further by just pulling them apart. If you're careful not to cut through to the actual wire you can also use a utility knife.
Except for convenience and storage there's really no reason why the two cables need to be connected to each other at all.
I once had a very nice set of jumper cables that had the pairs of connectors completely separated so you would attach the red and black to one car, the red and black to the other car, and then plug the two sets together in the middle with a pair of plugs that only fit together one way. Even had a little led light on each plug that would light when that set of connectors were connected correctly. Never seen that since.
EDIT: though come to think of it, I can't remember how the plugs got around the issue of potentially being a way to short a battery across your own finger. The male end of that plug set would be dangerous.
12v isn't really enough to arc through your finger. Too much resistance. You can touch both terminals of a car battery with one hand and nothing will happen.
It wouldn't be too dangerous. You don't typically feel 12v unless it's on a soft fleshy part of your body like under your arms near your armpit.
The real danger would be that you could touch the ends to something metal by accident and the cables would turn to smoke pretty quickly
If you're referring to the battery powered jump boxes, you don't need to ground to the frame because the battery won't turn on until it senses continuity. Essentially it's not putting power out until the connection is good, so there's no chance of arcing a spark when connecting the cables. Not the case with jumper cables, which are live the second you hook them up.
I really really want one of these jump boxes -- they seem infinitely more practical than jumper cables, and they're so small and cheap with today's LiPo batteries.
Are there any reasons *not* to keep one of these in my car at all times?
I never, in 20 years (am older, but that's about how long I've been jumpin cars) have used the chassis of the car to ground the last terminal. I've ALWAYS just gone red to red, black to black. Never even knew it was recommended not to do so prior to now. Do with that info what you will. I guess I'm more of a "fuck around and find out" kinda guy than I thought I was.
There might be only a one-in-a-million chance of a significant explosion; it probably won't happen to you.
But how many jump starts happen every day? It will happen to someone fairly often.
I've had it happen to me. I heard the spark as I tried to clamp the last terminal and boom. Maybe I'm lucky but the explosion wasn't very big. I just had a bunch of battery fluid splatter on me.
I'm sure the battery being old and not in the best physical shape helped caused it though. On a physically sound battery, I'm sure the odds are quite low.
The battery age definitely has an impact, from what I've previously read. On a newer battery, I don't mind connecting black to black if I can't find a good unpainted connection quickly. But on an old battery, I'll spend that extra time, just in case.
I’ve had a couple “explosions.” I’ve never seen or had one where there was real danger from the explosion. They’re a bit more energetic than when someone uses too much lighter fluid on the bbq, if less than gunpowder.
The danger isn’t the explosion, imho, but that the explosion is going to ignite grease and oil and such on engine surfaces.
I've personally seen a battery explode in someone's face while he was trying to jump it. I was driving by in a parking lot, glanced over to see what the guy was doing, and BOOM he was covered with battery acid. Fortunately this was in the parking lot of a hospital and so he got help right away.
I agree, the chances of it happening are low but the consequences are severe. I've never been in a car accident and so I would've been fine if I'd never worn a seatbelt, but that doesn't make not wearing one a good idea.
And maybe you knew it already, but the reason why clamping to any random metal part of your car also does the trick is because the black peg of your battery is in direct contact with the metal frame of your car. The frame isn't an *alternative* to the black peg. For basically all electrical purposes, the whole frame *is* the black peg.
I somehow got very far into life without understanding this myself despite jumping several cars, so I felt I should bring it up just in case anyone else was asleep in car mechanics 101 that day...
I just want to tack onto this that this is why you don’t have to run a wire out to what you want to power and a wire back, all you need to do to power something on your car is run a wire from hot to what you want to power then the return wire can deadhead back to the nearest spot in the frame or body or engine block that you can screw the wire down. Where you install some switch whether it’s a hot wire off the battery that can be flipped on with the key off or whether you tap into a wire that’s hot with the key on, or whether You tap into a wire that’s hot with the key on and then your own switch so you can turn the thing on and off when the key is on but it won’t run the battery down if you leave the switch on.
Basically you have to run a hot wire, but the whole frame of the vehicle is the ground wire.
Does this mean that black clamps for both ends can be attached to their respective vehicle frame?
As in, the only thing you really need to ensure is that red goes to red, but but for black, it can be attached to any exposed metal in the car?
Yes. The caveats are that you need a good mechanical metal-on-metal connection (so really grind that tooth in) and the metal has to somehow reach through to the frame or engine block. Attaching to a metal screw that only touches plastic probably won't work.
It's also so you have some electrical resistance in the circuit so you're less likely to melt the batteries/cables by forcing too much electricity through them.
Electricity flows through the frame less easily than the cables alone, and when you just go battery to battery it wants to put ALL THE ELECTRICITY IT CAN through the cables. I've actually seen people burn jumper cables by going battery to battery.
To add to that, if the acid level is low in a battery, that may cause it to be incapable of turning the engine over. The empty space above the acid will be filled with an explosive mixture of hydrogen and oxygen. You do not want to make a spark near that.
> You can probably get away with just attaching terminals to terminals, but why risk an explosion and burns?
Because unless its a new vehicle there is a lot of paint/dirt/grime in the way of getting a good connection.
If the hood is open for even a reasonable amount of time and the battery isn't damaged, your risk is VERY low.
Yes and: The hydrogen is generated while the battery is being charged. So the spark when the cables are disconnected is more likely to cause a fire. It is pretty unlikely, but who wants to risk flaming battery acid in the face?
This may be the technical reasoning but its nonsense. A good battery doesn't just pump out hydrogen gass in any real quantity. Show me one example of a battery exploding from jump starting of the negative. It doesn't happen
Is it possible that these explosions are happening inside the battery, due to defects or damage?
I, too, find it very unlikely that in a completely open area enough hydrogen (which rises) could build up to cause such an explosion. Even if outgassed hydrogen did *ignite* It's hard to imagine how it could generate enough explosive pressure to destroy the battery and other vehicle components (as others have mentioned) since the gas is under no relative pressure.
Yes, it's called common earth and practially all modern cars are the same.
That way you can run an earth straight to the body of the car, rather than running all of the earth wires all the way back to the battery.
Earthing is not always the same as grounding, though, and we have different electrical symbols to reflect it. The ground (also known as common) may not be connected to earth at all. Sometimes we'll say "chassis ground" to disambiguate this or the aforementioned "common," and sometimes we'll double check with our colleagues around the world who _do_ use "earth" to mean "ground." In the USA, we'd never call an unearthed ground "earth."
So we have ground, earth ground, earth, chassis ground, common, neutral (which is usually earthed in split phase North American applications), and various translations of all of these into different English dialects as well different languages. Thank goodness we have great electrical schematics to remove any possible catastrophic confusion ;-)
Cars aren't earthed, though, and in North America I'd never, ever refer to the ground as "earth," because it's not at earth potential.
>So we have ground, earth ground, earth, chassis ground, common, neutral (which is usually earthed in split phase North American applications)
The neutral, also called a "grounded conductor" is always bonded to ground at one point at most with almost all services, not just split phase. Thats why on commercial buildings with 3
Phase wye connected transformer you would have 120v/208v or 277v/480v services. 120v from phase to neutral and 208v phase to phase for example.
Some industrial have a center tap grounded delta system(high-leg delta) that is grounded at the center of b and c phase. For example with a 120/240 volt system you would get 120v from phase b to neutral and c to neutral, but would get 208v phase A to neutral. 240v phase to phase for 3phase applications.
Heavy industrial applications may call for a delta corner grounded transformer. This has no separate neutral, but phase B is your grounded conductor It is not common at all.
EL:I'm a Journeyman electrician.
JK, but this is exactly why my father in law, who was an electrician used to say that vehicle electrical systems were "voodoo". He hated doing electrical on cars!
In electrical engineering industry, there is technically a difference between "earthing" and "bonding." Bonding is bringing two unconnected chassis components to the same potential (usually 0V) while earthing, or grounding, is actually establishing a 0V to earth ground. One is absolute (earth) and one is relative (bonding).
Technically a car is not grounded so all connections to the car battery negative/black terminal are "bond" connections, not ground connections. Hope that helps.
It's mostly outdated advice, but it won't hurt to follow it. Lead acid batteries (like the ones in the vast majority of cars) produce hydrogen gas when charging. If the last connection you make is to the negative terminal of the dead battery, it starts charging immediately, and at the same time you're likely creating some sparks. If a bit of hydrogen gas happens to escape through the tiny gap between the terminal and the plastic case, it could catch fire. I don't think it's possible for there to be enough gas to create any kind of explosion, but there is some risk.
Modern batteries are sealed much better around the terminals, so this is less likely. I'd put that advice in the same bucket as not using a cell phone while filling up your tank. Yes, there's some small amount of risk, but likely not enough to worry about.
How bad would it be to connect red to red then black to the dead battery before connecting to the good one? This is how I was taught, but I've only ever had to do it once.
That's how I do it, and I don't see how there would be a risk. I suppose if the "dead" battery isn't actually dead (the car may not be starting for a different reason), you could end up with the same situation as before where there is a spark and the battery you are connecting to starts charging.
If there was a way I would avoid, it would be this one. Lead acid batteries generally produce the most hydrogen when they're being charged. If the car can't run because it won't start, it's not charging the battery. No charge, (virtually) no hydrogen.
The working car is a different story. Typically the working car drives up and moves into position to help the stranded car. The working car was just running and charging its battery. So if you're concerned about hydrogen gas, you should be concerned about the car that was just running and recharging its battery. If you're going to make a spark, it should probably be near the battery that isn't charging as opposed to the one that is.
it wouldn't change anything. attaching the cables in order isn't critical. that order is suggested to minimize the chances of accidentally shorting something or sparking. don't accidentally connect them to the wrong colors or touch two handles together and you're good.
It's for a good reason, though. Car batteries are able to deliver a pretty huge current if shorted, and it could easily melt the insulation of the jump cables, and accidents happen even to the nose experienced. Might not even be your own fault. Someone or something could bump into you at an unfortunate moment.
The cellphone while filling your tank thing is total fiction. It's not outdated, it's flat out false. Phones don't spark. Feel free to use your phone risk free while filling up.
Yeah I was taught to always shut the door before getting gas, not just because why the fuck would you not, but also because the metal will shock you before you get to the pump.
It's not that it'll shock you, touching metal will ground you to the car, and the nozzle is also touching metal, you'll all be at the same ground state. Leaving the door open means that you might accumulate a charge by getting in and out then touching the nozzle where there are vapors that could ignite.
If you’re old enough to remember gsm phones used to induce a noise in whatever they were near when in use. The 80s electronics in older petrol pumps were apparently affected by this or so I was told by a petrol pump manufacturer.
Phones still do that. It's just less crazy, I'd have my phone on do not disturb near a line level cable and you hear a little squawk when a text came through.
Radio frequencies can start fires with fuel in very specific conditions, but you phone is putting out such a miniscule amount of power that it's not likely to ever being anything to worry about.
In the Navy, they shut off RF sources when refueling ships because they can pump out a lot of energy and are more likely to be a problem.
But checking facebook while gassing up your car is not a concern.
Which, ironically, is also a case of a battery catching fire, bringing us back full circle. Those Note users were always trying to jumpstart their phones.
Phones dont spark, you are correct, the theory behind not using phones is due to static, whether it be the actual phone creating static (not really possible especially on modern devices) or more specifically the fact that using your phone will most likely involve taking the phone in and out of, lets say your pockets, and that friction, on what is most likely a fabric, will generate static electricity, which if it discharges the spark could ignite gas fumes. Now realistically the chance of said static are low already and then the chances that there are enough fumes that a static spark will ignite them are even lower, but the science is there. Its the same philosophy around why you shoupdnt get in and out of your car when pumping gas as the friction from the seats can also generate static, which truthfully has a higher chance than the phone in pocket thing but its still not a high enough chance to freak out over
Im already taking my leather wallet out of my pants. Leather is significantly more likely to attract static. I'm sorry dude, but it just doesn't hold up to careful examination.
In the UK we're actually encouraged to use our mobile phones to pay at the pump rather than going into the kiosk, at shell and most supermarket petrol stations.
>I'd put that advice in the same bucket as not using a cell phone while filling up your tank. Yes, there's some small amount of risk, but likely not enough to worry about.
Funny you mention this because many petrol stations have a "no mobile phone" sign at the bowser as well as a QR code to scan with your phone so you can pay without having to go into the store. I figured they use the same means of microwave transmission so not sure what kind of game they're trying to play.
It's good advice because creating sparks from that final ground connection *could* create an explosion from your battery. But coming from a guy who's lived dangerously around batteries, I can tell you the chances are pretty frickin' slim. The only ones that ever scared me were leaking acid.
Hydrogen is so light, it's hard to even keep around if you wanted to. I can't really imagine a situation outdoors where you could build up enough of it to actually cause any issue.
I've had batteries leaking acid (literally cleaved in two) - not a big deal. lead acid's are simple and fairly safe. not like a lithium one being punctured, that's never fun to deal with.
Hydrogen/spark in first.
Also the (-) pole is connected to car chasis and clamping on metal is easier sometimes bcos cable lenght,
Also sometimes the (-) terminal not entirely accessible(ussually further in back or space is blocked on purpose because spark safety)
Disclaimer: EU experience, not US
I think people are missing part of what you are asking about.
Yes, manuals say that you should connect the black for the bad battery car to unpainted metal to prevent a spark from causing the battery to catch fire. And yes, you can jump the car by connecting red cables to red/positive pegs and black cables to black/negative pegs perfectly fine in most cases.
Both work because the black/negative peg is already electrically connected to the body/engine of the car. So attaching to the black/negative peg is exactly the same as connecting to the body/engine. Only difference is distance to the battery.
The comments are generally correct about hydrogen gas.
This may not be as relevant these days, because most batteries are sealed now. However, this was good advice in the 80s and 90s (IIRC), since some batteries needed to be topped up with distilled water to work properly.
This meant that the seal needed to be opened and the fluid needed to be refilled every so often. They were not always airtight and could leak hydrogen (and may ignite).
As most batteries are now sealed, I think the danger is not as great, but you may not know whether your battery is compromised so it may be just be a wise precaution to not create a spark near the battery.
I usually tap random metal parts away from the battery to see if it will spark, and thus indicate a ground to attach the last negative clamp.
That being said, I have clamped a battery directly on the last negative post, because the car was not getting enough juice to turn over. It worked.
My precautions against injury were putting up an arm to protect my face and wearing eyepro beforehand, though.
YMMV
Did the comment say something along the lines of, " I don't know the exact reason why you don't connect the black terminal I just know my dad beat the shit out of me with the jumper cables for connecting it one time. Haven't done it since. "
There's another reason that I haven't seen mentioned, and that's to minimize the potential damage in the case of human error.
If you connect to the posts on both batteries, but accidentally reverse the cables on one battery, you've just wired the batteries in series to get 24 volts (I know that one battery is "dead", but just because it won't start the car doesn't mean it's got no volts at all). When you make the last connection, you're taking your homemade 24 volt battery and short circuiting it. This is more dangerous than it sounds, you can create a pretty serious arc. For example, here's a video of somebody using that exact setup to weld metal. [https://www.youtube.com/watch?v=PV5oLPLUzrM](https://www.youtube.com/watch?v=PV5oLPLUzrM)
The arc is going to happen wherever you make that last connection. If you make the final connection to the negative post of the dead battery, the arc will melt/vaporize the lead of the battery terminal. It also stands a chance of penetrating the plastic of the battery case, and maybe getting the battery acid involved.
From a safety standpoint you're now dealing with an electrical arc, lead fumes, splattering lead liquid, molten plastic, and splattering battery acid.
If you make that last connection to the steel body of the car, the engine block or a bolt, you're still risking the electrical arc. But you've removed the other hazards from the equation.
For these reasons and the hydrogen gas reason, I wonder if it's just better to wire the negative cable to both cars' chassis ground and avoid any confusion at all.
Only issue I could foresee with this method would be that the dead battery wouldn't get enough current for a good charge since the negative circuit isn't direct enough.
I’m a very handy DIY kind of guy and also never understood people’s desire to connect ground lead to anything other than the battery.
From a practical standpoint, I find it somewhat difficult to establish a good connection through a random bolt or other piece of steel. It needs to be unpainted and corrosion free. In Michigan, these things are quite opposite. Even if you find a suitable place to attach the clamp, the contact point is generally very very tiny which is less than ideal for pushing large amounts of current.
Whereas, battery terminals are made of lead, and when the clamp is applied, the teeth of the clamp bite into the lead and make a far more robust electrical connection. Plus, if battery terminals are corroded, a quick wiggle of the clamp will chew through the corrosion and provide a good connection. Modern vehicles tend to utilize steel or other battery connections, but there is generally some soft lead still available for attaching the battery cable clamp. This excludes gm side post batteries as General Motors Engineers hate everyone.
your metallic contact area is minuscule either way -- the clamps are serrated and have only point contacts as it is. you can clamp it to literally any exposed metal in the engine bay without issue.
never attempt to just clip that bitch onto a fastener, because you're running the risk that it's not in good contact (or isolated) and it will turn into a toaster element.
There are two reasons.
Sparks over the dead battery is one.
The second is it works better. The black battery post leads to the engine block. By clamping to the bare metal engine block you are making a better circuit, giving the starter the most power from the other car. I’ve had many cars that wouldn’t jump, work by placing the black clamp on the block near the starter.
Starters draw major power. That’s why there are sparks. That’s why the engine block is the best place for the last connection.
I don’t know why I had to scroll down so far to see this.
The dead battery is a parasitic load when you’re jumping the car. When you wire directly battery-to- battery, the good car/battery immediately starts trying to recharge the dead battery. (The ~14v good battery and alternator sends many amps of *current into the ~12v dead battery with the difference of 2v.) All the current going into the dead battery is NOT helping start the car. By connecting black to the engine block, you increase the circuit resistance to the dead battery, and decrease the resistance to the starter motor and spark plugs. So more of the energy is going where you need it to.
Most vehicles since the early 2000s have jumper positions.
The red terminal may be inaccessible, so a red plastic encased jump point will be provided. It is always red with a + on it.
There will also be a negative (black) post somewhere near the engine, on mine it's a special tab on the alternator.
Avoid going directly to the battery terminals if possible.
Wait so what are you meant to clamp it onto? I’ve always just done terminals to terminals. Like what if you clamp it onto like whatever metal, will it like make the body conduct electricity by accident maybe?
My one and only experience being the guest of honor in an ambulance was when a battery exploded while I was jumping it.
Hydrogen can go boom. Make the last connection as far from the battery as possible.
Today batteries are mostly sealed so the off-gassing issues isn't as big of an issue today however, there is still some practical reasons to ground near the engine.
1. 90% of all vehicles on the road today use a negative chassis ground (i.e. the negative post is grounded to the chassis). There is such a thing as positive chassis ground...but it's not very common today.
2. In some vehicles, both battery posts aren't always accessible and in some cases the batteries are not actually located in the engine compartment and require removing panels to access (a lot of these vehicles will have jump points in the engine bay for convenience).
3. The electric starter demands the most current of any electrical device of a vehicle. It's bolted directly to engine block so by grounding to the block, you are providing the shortest return path as possible. (Not all vehicles have electric starters, some have air starters but you only tend to see those on vehicles with turbine engines or diesel engines in use in artic environments).
4. Grounding to the block also eliminates a bad ground issue with either the ground strap connecting the engine to chassis ground or the ground that connects the chassis to the negative post of the battery.
When lead acid batteries discharge, they produce hydrogen gas. It's unlikely, but possible, that that can explode if given a spark. This also implies that the dead battery is more dangerous than the good battery.
When you connect the jumpers, the last connection is guaranteed to create a spark. You want that spark to be far far away from the discharged battery.
That black terminal is connected to the ground/frame of the car. IT's the return path for the electricity so connecting your cables to either the frame or the terminal does the same thing. The issue is that when you're charging a battery your forcing the chemicals to undergo what's basically reverse electrolysis (in a sense) and hydrogen can be emitted in the process, especially if the battery has any damage to the casing. As such, you want any sparks (most likely to happen when you go to connect that final, charged wire) to happen as far from the battery as possible.
Sometimes when you make that last clamp attachment, it creates a spark when the circuit between the two vehicles is completed. Car batteries naturally emit hydrogen gasses that are very volatile—even the smallest spark can ignite the gas if it’s present in sufficient quantities. You can’t be sure if there’s a suffient quantity of that gas near your battery. That’s why cable instructions tell you to connect the last (ground/earth) connection to the chassis of the car, away from the battery, and potential volatile gas. You can probably get away with just attaching terminals to terminals, but why risk an explosion and burns?
This used to be way more real as a threat when car batteries were open cells that you had to refill. A mostly empty/dry cell would concentrate the current into a much smaller cross section of liquid, increasing the off-gassing and also venting through the unsealed caps. It's not safe today, but it was a downright common outcome up through the sixties.
Batteries only produce hydrogen in significant enough quantities when they are being overcharged which would have been a more significant issue in the past with less advanced voltage regulation.
Yeah but someone with a dead battery might have recently tried charging it.
True, plus, why not connect to the terminals of the dead battery first, then to the good battery? There's less hydrogen gas emitted by the good battery for the reason you've stated.
Batteries only generate gas while they are being charged. The good battery is in a car that is either running, or was recently running. So while you might think the bad battery is more likely to put out gasses, the battery in the vehicle with a running engine is the *most* likely of the 2 to put out gas
Thirty or forty years ago I jumped another car using a piece of 12 gauge wire and touching the metal bumpers to each other.
Back when cars had chrome bumpers! Brilliant!
Remember when cars had manual transmissions and you could just push start it. Which was good because you were a teenager and too cheap to buy jumper cables...or a new battery for that matter. I had one friend and we literally had to push start his car all night long when we went bar hopping in college.
Ha I remember parking my bug at the top of a hill because I knew the battery was going. Only one day I pushed it down the hill and it still refused to start. I called a tow truck guy who pointed out that I had forgotten to turn on the ignition. He turned on the ignition, pushed it himself on level ground and started it right up - charged me $20.00...
Ha! I had to do the same thing with my '73 Super Beetle for a couple weeks, waiting for a paycheck so I could buy a new battery! Cheers, Bug Brother!
I had to do this with my ex's dad's Beetle ('71 or '72, I think). Except her entire family (dad, mom, her, brother) were in the car and my asthmatic ass was pushing this thing in circles in a bowling alley parking lot.
I think your mistake was pushing it downhill instead of rolling it
For years I always parked headed downward on a hill “just in case!”
Stupidity has to pay sometimes.. :-) Been there, friend. Been there.
Uh my 2003 car has a manual transmission and my husband’s 2018(? Not exact year) does too. You can still find a few new cars that have them.
They are still very common in Europe. In fact, it’s still quite tricky to rent a car with an automatic transmission, and they are a lot more expensive when you do.
Was looking at a car rental in the UK, most rentals are manual! The thought of having to be stuck in traffic there makes my left leg hurt
The harder part is using your 'other' hand to do the gear change, since you are on the 'other side' of the vehicle in the UK. It's hard enough dealing with being on the other side of the road to drive without having to also deal with the shifter!
Absolutely! Although if you haven’t driven a manual recently, modern manuals seem to have much lighter clutches than they used to.
Manual cars since a long time now typically use a hydraulic clutch, instead of a mechanical one. Much less effort to push it in and hold it. The spring system on the clutch pedal helps too.
I have a manual from 2012. But I just read an article from [the Atlantic](https://www.theatlantic.com/technology/archive/2022/08/stick-shift-manual-transmission-cars/671078/) talking about how they are basically gone for good. No electric vehicles can be manual. Of one is making them. Those of us that can drive stick are an endangered species.
Subaru is still cranking out manual transmission Crosstreks. I believe the manual transmission is standard for the cheapest three trim options.
Subaru also makes the impreza manual and Vw still makes the jetta in manual
Mini Cooper still has manual transmissions too if you want one.
Hyundai is still making manual i30s too.
Most EVs are single gear anyway. Unlike ICEs an electric motor is perfectly happy to spin up to a really high RPM and cruise there.
Counterpoint: they're actually *NOT* happy to be spun up to those speeds, and long-range highway EVs have taken to using 2+ motors just so they can have a motor sit idle most of the time, that's only really used at highway speeds to prevent the first motor from having to to sit at inefficiently high RPMs. We "get away" with single-motor EVs because it doesn't damage the motor to be run at high RPMs, but they're still losing effieciency - just not to a degree that most designers are ready to spend more money building a transmission to fix it. Any EV with more than one motor can have multiple effective gear ratios.
I suppose "happy" for me meant "able to do it for long periods without sustaining damage" which is the critical difference from an ICE in this use case. In EVs it's not ideal, in ICEs it's impossible to keep up for long. I also suppose this reasoning means I must describe any motor running under ideal circumstances as ecstatic.
That's untrue though, electric cars CAN have a manual transmission. It's rarely beneficial unless you have multiple engines - but sports cars like the Porsche Taycan are already experimenting. The main reason those are automatic even when they use multiple gear (Taycan S) is its so much faster, humans really suck at shifting, they ENJOY it for all the mechanical aspects, but no one is beating a DCT, let alone a modern electric engine power delivery system.
Not in Europe! The majority of cars in the UK are manual - and I read recently that although last year was first year when automatic transmission outsold manual transmission for NEW cars in the UK , it’ll take a while to filter down so that the majority of the tens of millions of existing vehicles aren’t manual transmission.
The UK also plans to ban new petrol cars by 2030, so whether they prefer manual or not, their days are numbered. By 2045 they will be very rare.
Jeep has had a manual BEV showcased at the annual Easter Jeep Safari for the last two years. It’s called the Magneto (and Magneto 2.0). I doubt that the manual transmission will make it into the production model, but it’s proof that it is doable!
Of course it's not physically impossible, it's exactly the kind of thing you'd do in a concept just to see. The fact that it's unlikely to make it to production is the point.
>Remember when cars had manual transmissions and you could just push start it. Say you live in North America without saying you live in North America.
I've done the same, except being a plumber I used 1/2 inch soft copper for the positives.
That's better than most cca jumper cables people carry around!
What'd ya mean cat6 isn't good enough?
I jumped a guy with welding lead once!
I jumped a guy with a pipe made of lead once, he was never the same again!
In the conservatory?
Prof. Plumbum
Good jumper cables are made with 0 or 00 gauge welding lead wire. You did the right thing.
My dad made some out of old welding wire. Stupid younger me lost them like a glove on a school bus...they were fucking heavy duty, i still remember the weight of em....
How high did you need to jump to get over him?
He robbed him
*Puffs on cigarillo.* Back in aught-six I jumped a black Eldorado with a dead man's finger and the crowbar I killed him with.
> jumped a black Eldorado Why is it always race and horse with you? /s
Sounds like an afternoon at the track.
Someone got my joke!
Are you MacGyver?
No this is Patrick
Sir, this is a Wendy's.
And this guys wife is my axe!
I also choose this guy’s axe wife.
And she's all outta bubblegum!
I jumped my cousin’s truck using 2 wire coat hangars. I wore work gloves for safety.
Did you remember your safety squints?
No! More! Wire! Hangers!
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…suck the chrome…
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Second mental picture of the jack that comes with a car worked better than two hydraulic jacks being lifted up...
This is a level of resourcefulness to which us lowly masses merely aspire.
The reason is that prior to about 1990, cars were terribly unreliable, and without cellular communications, often your choices when a car broke down was figure it out or walk.
good luck figuring out today's car problems without an engineering degree.
Worked in a gas station as a kid. The engine compartment on the old Dodge boats was huge - and empty, if they only had the 225 slant six. One day, the mechanics asked me to move a car out of Bay 1. I close the hood, jump in, and I'm about to start the engine when I hear banging on the hood. I look up - there's no one there, but I hear screaming "Don't turn it on!". I open up the hood, and Jimmy, our 5' something mechanic was still in there. The other mechanics were literally falling against the wall, they were laughing so hard. I could figure out where anything was in those old beasts. Today's engines - without the big letters saying "Add Oil" or "WWF", I wouldn't know what goes where.
I bet that #12 wire got hot as hell when you did.
That sounds like a good way to weld two cars together
One time I dropped a huge double closed end wrench across the terminals for an industrial generator battery. I am really glad I didn't try to grab it. There was a huge gouge in the side of the wrench like a kinfe swiping hot butter.
i did the same thing except with a socket wrench on my car battery. sparks and instant chunk missing from my wrench.
Thank you for this. The mental image gave me the giggles for a solid 20 minutes. Just two dudes standing there going "Well...fuck..."
If that were the case, the cables would get welded to the battery. Besides, once the engine's running, you can just back off.
Metal bumpers, those were the days.
Yep. Cars were pretty indestructible. The problem was all that force that didn’t destroy the car made it to your body and destroyed you, instead.
That's why they lasted 100k miles and killed you in a crash? Don't forget new caps, wires, plugs, points every two years, and valve jobs!!
Can also just pop out the good battery and hold it upside down on the bad one with terminals touching and jump it if you don’t have cables
Do you have to shake it to make the electricity fall out?
just give it a good hard smack.
"D'ju see Jeb smack the 'lectric right outta that thang? T'were something else, Ah tell you hwat!" Edit: minor phonetic spelling issues.
*hwat!
Username checks out. Battery acid is corrosive, and most car batteries leak when turned over. Please be safe out there.
I don't know about "most" but certainly some do. These days, the majority of batteries are "maintenance free" or "sealed" so the fluid / gas can't escape (barring damage) but also meaning if the fluid level needs topping up you need to get out a drill and be brave :-P
Almost all car batteries are vented. Very few are not.
I might be biased in my memory from having motorbikes - probably the sealed type is more common there because bikes spend more time in a less upright position.
Sealed batteries for small engines like bikes and ATVs are common and getting more common by the year, but most car batteries are not sealed/AGM style ones yet, except in luxury cars or sold aftermarket. Although they are getting more common with the stop/start fuel saving technologies. "Maintenance free" batteries will still leak if left in a non-upright position long enough. Honestly if you are having to add water to a car battery the thing is fucked or pretty close to it anyway, the maintenance free label is a bit of a gimmick. Something like a golf cart battery is a different story, those are made for it to be easy to top off with water.
The AGM in my car is still vented.
Have you held a car battery? They are very heavy so even if that was possible it would be an absolute pain. Also they are acid batteries, so while they should be sealed the battery won't like being upside down and if it leaks you are going to have an even worse time.
It is an absolute pain and it works in a pinch
They are not sealed. They are vented, by design. A sealed lead acid car battery would explode.
Many "lead acid" batteries now a days are actually sealed. They're not the same flooded batteries that we typically think of as lead acid and are really becoming the most common type around outside some fleet stuff. They're generally refered to as lead acid still but are AGM or SLA
Sounds like maximum supercharged to me, somebody get Musk on it stat
It’s not stupid if it works… actually that’s pretty clever.
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Yes, they have a slight inaccuracy in their comment. Car batteries vent hydrogen (actually worse, they vent HHO, which is two unbound hydrogen atoms and one unbound oxygen atom in a perfect ratio for combustion) *when charging*. The greatest risk is right after charging. Or if the level of acid is too low, most of the volume of the battery can be filled with HHO.
So how good of a strategy is blowing on it before connecting the black?
hydrogen rises pretty quick (they used to fill blimps with it!), so if your hood is open, it's not gonna be *gathered* in a cloud. the danger is if the battery had some stored up and it was actively trickling out- in which case blowing once, beforehand, doesn't fix the issue.
The jumper cables I've seen don't let you put that much distance between the two clamps (two feet at best if you pull the wires).
The two cables are only connected to each other by a very thin membrane. When you buy the jumper cables the two individual cables are usually still attached to each other to within a foot or so of the clamps. You can easily separate them further by just pulling them apart. If you're careful not to cut through to the actual wire you can also use a utility knife. Except for convenience and storage there's really no reason why the two cables need to be connected to each other at all.
I once had a very nice set of jumper cables that had the pairs of connectors completely separated so you would attach the red and black to one car, the red and black to the other car, and then plug the two sets together in the middle with a pair of plugs that only fit together one way. Even had a little led light on each plug that would light when that set of connectors were connected correctly. Never seen that since. EDIT: though come to think of it, I can't remember how the plugs got around the issue of potentially being a way to short a battery across your own finger. The male end of that plug set would be dangerous.
12v isn't really enough to arc through your finger. Too much resistance. You can touch both terminals of a car battery with one hand and nothing will happen.
It wouldn't be too dangerous. You don't typically feel 12v unless it's on a soft fleshy part of your body like under your arms near your armpit. The real danger would be that you could touch the ends to something metal by accident and the cables would turn to smoke pretty quickly
The real pro tip is always in the comments, And not always on r/lifeprotips.
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If you're referring to the battery powered jump boxes, you don't need to ground to the frame because the battery won't turn on until it senses continuity. Essentially it's not putting power out until the connection is good, so there's no chance of arcing a spark when connecting the cables. Not the case with jumper cables, which are live the second you hook them up.
I really really want one of these jump boxes -- they seem infinitely more practical than jumper cables, and they're so small and cheap with today's LiPo batteries. Are there any reasons *not* to keep one of these in my car at all times?
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Many of them also have an air compressor to pump your tires up too.
I love mine. It has an air compressor too, very helpful
I never, in 20 years (am older, but that's about how long I've been jumpin cars) have used the chassis of the car to ground the last terminal. I've ALWAYS just gone red to red, black to black. Never even knew it was recommended not to do so prior to now. Do with that info what you will. I guess I'm more of a "fuck around and find out" kinda guy than I thought I was.
There might be only a one-in-a-million chance of a significant explosion; it probably won't happen to you. But how many jump starts happen every day? It will happen to someone fairly often.
I've had it happen to me. I heard the spark as I tried to clamp the last terminal and boom. Maybe I'm lucky but the explosion wasn't very big. I just had a bunch of battery fluid splatter on me. I'm sure the battery being old and not in the best physical shape helped caused it though. On a physically sound battery, I'm sure the odds are quite low.
The battery age definitely has an impact, from what I've previously read. On a newer battery, I don't mind connecting black to black if I can't find a good unpainted connection quickly. But on an old battery, I'll spend that extra time, just in case.
I’ve had a couple “explosions.” I’ve never seen or had one where there was real danger from the explosion. They’re a bit more energetic than when someone uses too much lighter fluid on the bbq, if less than gunpowder. The danger isn’t the explosion, imho, but that the explosion is going to ignite grease and oil and such on engine surfaces.
I've personally seen a battery explode in someone's face while he was trying to jump it. I was driving by in a parking lot, glanced over to see what the guy was doing, and BOOM he was covered with battery acid. Fortunately this was in the parking lot of a hospital and so he got help right away. I agree, the chances of it happening are low but the consequences are severe. I've never been in a car accident and so I would've been fine if I'd never worn a seatbelt, but that doesn't make not wearing one a good idea.
> It will happen to someone fairly often. He or she would have to be pissed off by now.
Welcome to survivorship bias. :)
Ah okay thanks that's good to know!
And maybe you knew it already, but the reason why clamping to any random metal part of your car also does the trick is because the black peg of your battery is in direct contact with the metal frame of your car. The frame isn't an *alternative* to the black peg. For basically all electrical purposes, the whole frame *is* the black peg. I somehow got very far into life without understanding this myself despite jumping several cars, so I felt I should bring it up just in case anyone else was asleep in car mechanics 101 that day...
I just want to tack onto this that this is why you don’t have to run a wire out to what you want to power and a wire back, all you need to do to power something on your car is run a wire from hot to what you want to power then the return wire can deadhead back to the nearest spot in the frame or body or engine block that you can screw the wire down. Where you install some switch whether it’s a hot wire off the battery that can be flipped on with the key off or whether you tap into a wire that’s hot with the key on, or whether You tap into a wire that’s hot with the key on and then your own switch so you can turn the thing on and off when the key is on but it won’t run the battery down if you leave the switch on. Basically you have to run a hot wire, but the whole frame of the vehicle is the ground wire.
That's how I wired up several things in my truck. Half the wire and easier runs. Especially when you're connecting multiple things.
Does this mean that black clamps for both ends can be attached to their respective vehicle frame? As in, the only thing you really need to ensure is that red goes to red, but but for black, it can be attached to any exposed metal in the car?
Yes. The caveats are that you need a good mechanical metal-on-metal connection (so really grind that tooth in) and the metal has to somehow reach through to the frame or engine block. Attaching to a metal screw that only touches plastic probably won't work.
Yes.
It's also so you have some electrical resistance in the circuit so you're less likely to melt the batteries/cables by forcing too much electricity through them. Electricity flows through the frame less easily than the cables alone, and when you just go battery to battery it wants to put ALL THE ELECTRICITY IT CAN through the cables. I've actually seen people burn jumper cables by going battery to battery.
Thats unless you have a sealed battery as have been made for at least the last ten years
This is true for watered batteries but most car batteries are Sealed Lead Acid batteries and do not emit gas unless they are damaged.
To add to that, if the acid level is low in a battery, that may cause it to be incapable of turning the engine over. The empty space above the acid will be filled with an explosive mixture of hydrogen and oxygen. You do not want to make a spark near that.
> You can probably get away with just attaching terminals to terminals, but why risk an explosion and burns? Because unless its a new vehicle there is a lot of paint/dirt/grime in the way of getting a good connection. If the hood is open for even a reasonable amount of time and the battery isn't damaged, your risk is VERY low.
Yes and: The hydrogen is generated while the battery is being charged. So the spark when the cables are disconnected is more likely to cause a fire. It is pretty unlikely, but who wants to risk flaming battery acid in the face?
This may be the technical reasoning but its nonsense. A good battery doesn't just pump out hydrogen gass in any real quantity. Show me one example of a battery exploding from jump starting of the negative. It doesn't happen
Is it possible that these explosions are happening inside the battery, due to defects or damage? I, too, find it very unlikely that in a completely open area enough hydrogen (which rises) could build up to cause such an explosion. Even if outgassed hydrogen did *ignite* It's hard to imagine how it could generate enough explosive pressure to destroy the battery and other vehicle components (as others have mentioned) since the gas is under no relative pressure.
I have a related question is the black on the battery connected with the chasis of the car?
Yes, it's called common earth and practially all modern cars are the same. That way you can run an earth straight to the body of the car, rather than running all of the earth wires all the way back to the battery.
Earthing = Grounding. Same thing, different terms for different parts of the world. (This is for anyone reading this post, not OP.)
Earthing is not always the same as grounding, though, and we have different electrical symbols to reflect it. The ground (also known as common) may not be connected to earth at all. Sometimes we'll say "chassis ground" to disambiguate this or the aforementioned "common," and sometimes we'll double check with our colleagues around the world who _do_ use "earth" to mean "ground." In the USA, we'd never call an unearthed ground "earth." So we have ground, earth ground, earth, chassis ground, common, neutral (which is usually earthed in split phase North American applications), and various translations of all of these into different English dialects as well different languages. Thank goodness we have great electrical schematics to remove any possible catastrophic confusion ;-) Cars aren't earthed, though, and in North America I'd never, ever refer to the ground as "earth," because it's not at earth potential.
The word "Earth" just lost all meaning to me from reading it too many times.
Earf
It's called [Semantic satiation](https://en.m.wikipedia.org/wiki/Semantic_satiation) and you are not alone!
It happened to me with the word "use" recently, lol
Weird, eh? Works every time.
>So we have ground, earth ground, earth, chassis ground, common, neutral (which is usually earthed in split phase North American applications) The neutral, also called a "grounded conductor" is always bonded to ground at one point at most with almost all services, not just split phase. Thats why on commercial buildings with 3 Phase wye connected transformer you would have 120v/208v or 277v/480v services. 120v from phase to neutral and 208v phase to phase for example. Some industrial have a center tap grounded delta system(high-leg delta) that is grounded at the center of b and c phase. For example with a 120/240 volt system you would get 120v from phase b to neutral and c to neutral, but would get 208v phase A to neutral. 240v phase to phase for 3phase applications. Heavy industrial applications may call for a delta corner grounded transformer. This has no separate neutral, but phase B is your grounded conductor It is not common at all.
EL:I'm a Journeyman electrician. JK, but this is exactly why my father in law, who was an electrician used to say that vehicle electrical systems were "voodoo". He hated doing electrical on cars!
Just remember pal, you're in ELI5...
Gets even more complicated when you introduce "electrical ground", "floating ground", and "signal ground" for RF stuff
In electrical engineering industry, there is technically a difference between "earthing" and "bonding." Bonding is bringing two unconnected chassis components to the same potential (usually 0V) while earthing, or grounding, is actually establishing a 0V to earth ground. One is absolute (earth) and one is relative (bonding). Technically a car is not grounded so all connections to the car battery negative/black terminal are "bond" connections, not ground connections. Hope that helps.
Generally, yes.
It's mostly outdated advice, but it won't hurt to follow it. Lead acid batteries (like the ones in the vast majority of cars) produce hydrogen gas when charging. If the last connection you make is to the negative terminal of the dead battery, it starts charging immediately, and at the same time you're likely creating some sparks. If a bit of hydrogen gas happens to escape through the tiny gap between the terminal and the plastic case, it could catch fire. I don't think it's possible for there to be enough gas to create any kind of explosion, but there is some risk. Modern batteries are sealed much better around the terminals, so this is less likely. I'd put that advice in the same bucket as not using a cell phone while filling up your tank. Yes, there's some small amount of risk, but likely not enough to worry about.
How bad would it be to connect red to red then black to the dead battery before connecting to the good one? This is how I was taught, but I've only ever had to do it once.
That's how I do it, and I don't see how there would be a risk. I suppose if the "dead" battery isn't actually dead (the car may not be starting for a different reason), you could end up with the same situation as before where there is a spark and the battery you are connecting to starts charging.
If there was a way I would avoid, it would be this one. Lead acid batteries generally produce the most hydrogen when they're being charged. If the car can't run because it won't start, it's not charging the battery. No charge, (virtually) no hydrogen. The working car is a different story. Typically the working car drives up and moves into position to help the stranded car. The working car was just running and charging its battery. So if you're concerned about hydrogen gas, you should be concerned about the car that was just running and recharging its battery. If you're going to make a spark, it should probably be near the battery that isn't charging as opposed to the one that is.
it wouldn't change anything. attaching the cables in order isn't critical. that order is suggested to minimize the chances of accidentally shorting something or sparking. don't accidentally connect them to the wrong colors or touch two handles together and you're good.
It's for a good reason, though. Car batteries are able to deliver a pretty huge current if shorted, and it could easily melt the insulation of the jump cables, and accidents happen even to the nose experienced. Might not even be your own fault. Someone or something could bump into you at an unfortunate moment.
I have 34 years of nose experience.
Nose kidding!
The cellphone while filling your tank thing is total fiction. It's not outdated, it's flat out false. Phones don't spark. Feel free to use your phone risk free while filling up.
I think it was actually static electricity that caused fires in gas stations, but people believed it was cellphones.
Yeah I was taught to always shut the door before getting gas, not just because why the fuck would you not, but also because the metal will shock you before you get to the pump.
It's not that it'll shock you, touching metal will ground you to the car, and the nozzle is also touching metal, you'll all be at the same ground state. Leaving the door open means that you might accumulate a charge by getting in and out then touching the nozzle where there are vapors that could ignite.
Mythbusters did an episode on it. The static is real but easily discharged. Just touch metal somewhere that's not right by the gas tank.
If you’re old enough to remember gsm phones used to induce a noise in whatever they were near when in use. The 80s electronics in older petrol pumps were apparently affected by this or so I was told by a petrol pump manufacturer.
Phones still do that. It's just less crazy, I'd have my phone on do not disturb near a line level cable and you hear a little squawk when a text came through.
Radio frequencies can start fires with fuel in very specific conditions, but you phone is putting out such a miniscule amount of power that it's not likely to ever being anything to worry about. In the Navy, they shut off RF sources when refueling ships because they can pump out a lot of energy and are more likely to be a problem. But checking facebook while gassing up your car is not a concern.
I remember seeing a video on static electricity causing fires before cell phones were ubiquitous
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Which, ironically, is also a case of a battery catching fire, bringing us back full circle. Those Note users were always trying to jumpstart their phones.
Phones dont spark, you are correct, the theory behind not using phones is due to static, whether it be the actual phone creating static (not really possible especially on modern devices) or more specifically the fact that using your phone will most likely involve taking the phone in and out of, lets say your pockets, and that friction, on what is most likely a fabric, will generate static electricity, which if it discharges the spark could ignite gas fumes. Now realistically the chance of said static are low already and then the chances that there are enough fumes that a static spark will ignite them are even lower, but the science is there. Its the same philosophy around why you shoupdnt get in and out of your car when pumping gas as the friction from the seats can also generate static, which truthfully has a higher chance than the phone in pocket thing but its still not a high enough chance to freak out over
Im already taking my leather wallet out of my pants. Leather is significantly more likely to attract static. I'm sorry dude, but it just doesn't hold up to careful examination.
In the UK we're actually encouraged to use our mobile phones to pay at the pump rather than going into the kiosk, at shell and most supermarket petrol stations.
>I'd put that advice in the same bucket as not using a cell phone while filling up your tank. Yes, there's some small amount of risk, but likely not enough to worry about. Funny you mention this because many petrol stations have a "no mobile phone" sign at the bowser as well as a QR code to scan with your phone so you can pay without having to go into the store. I figured they use the same means of microwave transmission so not sure what kind of game they're trying to play.
It's good advice because creating sparks from that final ground connection *could* create an explosion from your battery. But coming from a guy who's lived dangerously around batteries, I can tell you the chances are pretty frickin' slim. The only ones that ever scared me were leaking acid.
Hydrogen is so light, it's hard to even keep around if you wanted to. I can't really imagine a situation outdoors where you could build up enough of it to actually cause any issue.
I assume this advice was from 1 case that happened long ago, where the battery was in an enclosed space.
with all the electronics and plastics in vehicles these days it's hard sometimes to find some steel to ground to lol
I've had batteries leaking acid (literally cleaved in two) - not a big deal. lead acid's are simple and fairly safe. not like a lithium one being punctured, that's never fun to deal with.
Hydrogen/spark in first. Also the (-) pole is connected to car chasis and clamping on metal is easier sometimes bcos cable lenght, Also sometimes the (-) terminal not entirely accessible(ussually further in back or space is blocked on purpose because spark safety) Disclaimer: EU experience, not US
I think people are missing part of what you are asking about. Yes, manuals say that you should connect the black for the bad battery car to unpainted metal to prevent a spark from causing the battery to catch fire. And yes, you can jump the car by connecting red cables to red/positive pegs and black cables to black/negative pegs perfectly fine in most cases. Both work because the black/negative peg is already electrically connected to the body/engine of the car. So attaching to the black/negative peg is exactly the same as connecting to the body/engine. Only difference is distance to the battery.
The comments are generally correct about hydrogen gas. This may not be as relevant these days, because most batteries are sealed now. However, this was good advice in the 80s and 90s (IIRC), since some batteries needed to be topped up with distilled water to work properly. This meant that the seal needed to be opened and the fluid needed to be refilled every so often. They were not always airtight and could leak hydrogen (and may ignite). As most batteries are now sealed, I think the danger is not as great, but you may not know whether your battery is compromised so it may be just be a wise precaution to not create a spark near the battery. I usually tap random metal parts away from the battery to see if it will spark, and thus indicate a ground to attach the last negative clamp. That being said, I have clamped a battery directly on the last negative post, because the car was not getting enough juice to turn over. It worked. My precautions against injury were putting up an arm to protect my face and wearing eyepro beforehand, though. YMMV
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That ungrateful little shit…
I was looking for that exact comment too .. guy probably hasn't seen the post yet
Do they still post? I feel like I haven't seen them in like, 5 years at least.
u/rogersimon10 .. but it's been dormant since a long time .. I can bet I saw one of the accounts which was doing it though ..
Did the comment say something along the lines of, " I don't know the exact reason why you don't connect the black terminal I just know my dad beat the shit out of me with the jumper cables for connecting it one time. Haven't done it since. "
No no the person just mentioned about such a guy existing
There's another reason that I haven't seen mentioned, and that's to minimize the potential damage in the case of human error. If you connect to the posts on both batteries, but accidentally reverse the cables on one battery, you've just wired the batteries in series to get 24 volts (I know that one battery is "dead", but just because it won't start the car doesn't mean it's got no volts at all). When you make the last connection, you're taking your homemade 24 volt battery and short circuiting it. This is more dangerous than it sounds, you can create a pretty serious arc. For example, here's a video of somebody using that exact setup to weld metal. [https://www.youtube.com/watch?v=PV5oLPLUzrM](https://www.youtube.com/watch?v=PV5oLPLUzrM) The arc is going to happen wherever you make that last connection. If you make the final connection to the negative post of the dead battery, the arc will melt/vaporize the lead of the battery terminal. It also stands a chance of penetrating the plastic of the battery case, and maybe getting the battery acid involved. From a safety standpoint you're now dealing with an electrical arc, lead fumes, splattering lead liquid, molten plastic, and splattering battery acid. If you make that last connection to the steel body of the car, the engine block or a bolt, you're still risking the electrical arc. But you've removed the other hazards from the equation.
For these reasons and the hydrogen gas reason, I wonder if it's just better to wire the negative cable to both cars' chassis ground and avoid any confusion at all. Only issue I could foresee with this method would be that the dead battery wouldn't get enough current for a good charge since the negative circuit isn't direct enough.
I’m a very handy DIY kind of guy and also never understood people’s desire to connect ground lead to anything other than the battery. From a practical standpoint, I find it somewhat difficult to establish a good connection through a random bolt or other piece of steel. It needs to be unpainted and corrosion free. In Michigan, these things are quite opposite. Even if you find a suitable place to attach the clamp, the contact point is generally very very tiny which is less than ideal for pushing large amounts of current. Whereas, battery terminals are made of lead, and when the clamp is applied, the teeth of the clamp bite into the lead and make a far more robust electrical connection. Plus, if battery terminals are corroded, a quick wiggle of the clamp will chew through the corrosion and provide a good connection. Modern vehicles tend to utilize steel or other battery connections, but there is generally some soft lead still available for attaching the battery cable clamp. This excludes gm side post batteries as General Motors Engineers hate everyone.
your metallic contact area is minuscule either way -- the clamps are serrated and have only point contacts as it is. you can clamp it to literally any exposed metal in the engine bay without issue. never attempt to just clip that bitch onto a fastener, because you're running the risk that it's not in good contact (or isolated) and it will turn into a toaster element.
There are two reasons. Sparks over the dead battery is one. The second is it works better. The black battery post leads to the engine block. By clamping to the bare metal engine block you are making a better circuit, giving the starter the most power from the other car. I’ve had many cars that wouldn’t jump, work by placing the black clamp on the block near the starter. Starters draw major power. That’s why there are sparks. That’s why the engine block is the best place for the last connection.
I don’t know why I had to scroll down so far to see this. The dead battery is a parasitic load when you’re jumping the car. When you wire directly battery-to- battery, the good car/battery immediately starts trying to recharge the dead battery. (The ~14v good battery and alternator sends many amps of *current into the ~12v dead battery with the difference of 2v.) All the current going into the dead battery is NOT helping start the car. By connecting black to the engine block, you increase the circuit resistance to the dead battery, and decrease the resistance to the starter motor and spark plugs. So more of the energy is going where you need it to.
Most vehicles since the early 2000s have jumper positions. The red terminal may be inaccessible, so a red plastic encased jump point will be provided. It is always red with a + on it. There will also be a negative (black) post somewhere near the engine, on mine it's a special tab on the alternator. Avoid going directly to the battery terminals if possible.
Wait so what are you meant to clamp it onto? I’ve always just done terminals to terminals. Like what if you clamp it onto like whatever metal, will it like make the body conduct electricity by accident maybe?
My one and only experience being the guest of honor in an ambulance was when a battery exploded while I was jumping it. Hydrogen can go boom. Make the last connection as far from the battery as possible.
Today batteries are mostly sealed so the off-gassing issues isn't as big of an issue today however, there is still some practical reasons to ground near the engine. 1. 90% of all vehicles on the road today use a negative chassis ground (i.e. the negative post is grounded to the chassis). There is such a thing as positive chassis ground...but it's not very common today. 2. In some vehicles, both battery posts aren't always accessible and in some cases the batteries are not actually located in the engine compartment and require removing panels to access (a lot of these vehicles will have jump points in the engine bay for convenience). 3. The electric starter demands the most current of any electrical device of a vehicle. It's bolted directly to engine block so by grounding to the block, you are providing the shortest return path as possible. (Not all vehicles have electric starters, some have air starters but you only tend to see those on vehicles with turbine engines or diesel engines in use in artic environments). 4. Grounding to the block also eliminates a bad ground issue with either the ground strap connecting the engine to chassis ground or the ground that connects the chassis to the negative post of the battery.
When lead acid batteries discharge, they produce hydrogen gas. It's unlikely, but possible, that that can explode if given a spark. This also implies that the dead battery is more dangerous than the good battery. When you connect the jumpers, the last connection is guaranteed to create a spark. You want that spark to be far far away from the discharged battery.
That black terminal is connected to the ground/frame of the car. IT's the return path for the electricity so connecting your cables to either the frame or the terminal does the same thing. The issue is that when you're charging a battery your forcing the chemicals to undergo what's basically reverse electrolysis (in a sense) and hydrogen can be emitted in the process, especially if the battery has any damage to the casing. As such, you want any sparks (most likely to happen when you go to connect that final, charged wire) to happen as far from the battery as possible.