Today I found my aging (but well-loved) Quashqai with a flat battery. Fortunately I had some jump-leads in the boot, and found a friendly person to help jump-start it. Without really thinking, I just did it using the process I was taught many years ago. When I got home, I checked on the official recommendation to see if I had actually done it correctly and, apparently, I *could* have caused an explosion as I did it slightly incorrectly.
So, without Googling, what is the correct procedure for jump-starting a car?
Red cable to the dead car
Red cable to the good car
Black cable to the good car
Black cable to a good earth point on the dead car...but battery -ve is generally fine.
I was always told They key bit is the last connection should not be to a battery. Because thats when the sparks happen.
As long as you can find a good earth point, do it that way. Otherwise the negative terminal is fine providing you're careful.
Although I've only ever jumped diesel cars/vans so maybe take that with a pinch of salt.
Strictly speaking isnt it by rolling out gear, then putting it in et. Or is rhat defined as a bump start?
Yeah, that's a bump start
Strictly speaking isnt it by rolling out gear, then putting it in et. Or is rhat defined as a bump start?
Thats bump starting, but I suspect most modern cars can’t be bump started as the power required for all the electrical systems, engine ECU etc to boot up would mean that they aren’t energised no matter how fast you push it before dumping the clutch.
The reason for not making that final connection to the -ve post of the battery is that the little spark that is made can ignite the small amount of Hydrogen made by a lead acid battery.
But as soon as you've opened the bonnet, Hydrogen is so light it'll dissipate into the air, so the risk is quite theoretical.
Do one lead at once rather than have two ends flapping about which could touch. The final connection should be to an earthing point or, if you can't find one(*) then to the negative terminal on the flat battery.
IIRC the recommended order was dead +ve, good +ve, good -ve, dead earth/-ve but I don't expect it really matters.
without Googling
I replied without googling or reading the rest of the thread, so basically what dave661350 said in the very first reply.
Also DON'T let a metal spanner touch both battery terminals at the same time, 'cause that makes welding come alive 😎
Quite a few cars have earthing points near the battery to connect the jump lead to. Certainly, my old Range Rover, which used to leak electricity and need jump starting regularly, had a special earthing point which it recommended you use. Basically just a lump of metal sticking out of the chassis
Yeah, you’ve all got it right . Apparently, modern sealed batteries aren’t really an issue but I had no idea. I’d got everything right apart from the final earthing bit. Still, I didn’t die yet.
The batteries on my transit are under the front seat so it has a positive near the fuse box under the bonnet and a massive metal lump sticking up from the engine block for the negative. I don't know if this common or just a Transit thing
Oh, and really give it some beans on the good car
Thats bump starting, but I suspect most modern cars can’t be bump started as the power required for all the electrical systems, engine ECU etc to boot up would mean that they aren’t energised no matter how fast you push it before dumping the clutch.
You can’t bump start an automatic.
Quite a few cars have earthing points near the battery to connect the jump lead to. Certainly, my old Range Rover, which used to leak electricity and need jump starting regularly, had a special earthing point which it recommended you use. Basically just a lump of metal sticking out of the chassis
This. I got very used to having to jump-start cars, vans, etc., with flat batteries, because where I was working last, we had a couple of thousand cars scattered around in various storage areas, some for weeks/months at a time. For a while my job was following a list and checking battery condition and tyres, for any that might have low pressure and highlighting them.
There were a couple of occasions when even a breakdown vehicle couldn’t start something that had been in storage and they had to be taken off site.
And yes, there’s often a proper contact point for attaching jump leads to, a few vehicles have the battery stuck away in very odd locations - a BMW had it in the boot, IIRC, and others back under the scuttle at the back of the engine bay! A royal PITA.
I was always told They key bit is the last connection should not be to a battery. Because thats when the sparks happen.
Yes, I've seen a guy blow up a battery by connecting to the negative terminal and causing a spark. Final connection should be to the chassis, well away from the battery.
Oh, and really give it some beans on the good car
I've heard this before but don't understand it. The good car doesn't even need to be running, surely?
Oh, and really give it some beans on the good car
I've heard this before but don't understand it. The good car doesn't even need to be running, surely?
It potentially doesn't need to be but it should be. Or you could end up with one half empty and one half full battery.
It also raises the voltage a bit which helps things along because more voltage means more current and every little helps.
It also raises the voltage a bit which helps things along because more voltage means more current and every little helps.
Okay, fair enough, but this still only needs it ticking over; the alternator will supply whatever current is pulled by the 'bad' car and it's unlikely to pull enough to make the good car stall. I guess you could say "increase the revs a bit" on the good car to be sure, but "giving it some beans" is overkill
I guess you could say "increase the revs a bit" on the good car to be sure, but "giving it some beans" is overkill
I've been in this situation and the flat car refused to start until I revved my car pretty hard. This was a petrol trying to start a diesel.
As above its not about the car stalling its about actually getting the other car to start.
Honestly, I'm not trying to be argumentative, I'm trying to understand.
The bad car needs current to start. It doesn't have enough current in its own battery so you use the battery from another, 'good', car. That battery can supply enough current on its own (otherwise the good car wouldn't be able to start either), which is why I said that you shouldn't really need the good car to be running at all.
However, I kind of get that running (i.e. ticking over) = higher voltage across the terminals, which is probably helpful, but why does revving the good car do that makes it more likely that the bad car will start?
As I understand it, the alternator supplies the current to the battery and it does it based on load, so if more current is needed (like because of the draw from the bad car's starter motor), the alternator will supply it, and even a ticking over engine would be able to supply the amount of charge needed, right?
What am I missing?
The explosion thing is ancient rubbish, it's far more important to get the order of connections correct. The reason the negative goes last is because of the risk that if it's done first, then just brushing any metal component with the positive end will short the donor battery through whatever it's just touched.
You can’t bump start an automatic.
You also can’t bump start a diesel which we found out the hard way by trying to push start a rented minibus round a car park and writing off the engine in the process.
Having recently had to jump start a neighbour’s car there was something in the manual about putting the heated rear screen on to absorb any voltage spikes?
Having recently had to jump start a neighbour’s car there was something in the manual about putting the heated rear screen on to absorb any voltage spikes?
Nah, that's just to keep your hands warm.
Having recently had to jump start a neighbour’s car there was something in the manual about putting the heated rear screen on to absorb any voltage spikes?
Nah, that's just to keep your hands warm.
Why does a lada have a heated rear window...
The batteries on my transit are under the front seat so it has a positive near the fuse box under the bonnet and a massive metal lump sticking up from the engine block for the negative. I don't know if this common or just a Transit thing
I think with a few transit sized vans it can be a case of "well surely it must have a battery somewhere" In my boxer and previous sprinter it's under the carpet in the passenger footwell. In the sprinter you had to remove the carpet which revealed the jack - take that out, then, take out the plastic housing for the jack, then upbolt the floor panel to get to it.
In the engine compartment there was a red pull out doofer that gave a positive connection for jumpstarting - which was somehow stark-staringly obvious every time you opened the bonnet until the one time you needed to jump start something when it would magically become completely invisible - in fact I'm certain that it just disappears completely.
In the engine compartment there was a red pull out doofer that gave a positive connection for jumpstarting - which was somehow stark-staringly obvious every time you opened the bonnet until the one time you needed to jump start something when it would magically become completely invisible - in fact I'm certain that it just disappears completely.
Audi A4 - battery in the boot, there are two terminals on the right side of the engine bay for connecting jump leads.
My van has a sticker pointing to the earthing point as the negative is tucked away out of reach. I carry a jump battery, and have used it a few times on other people's cars, not mine. We camp quite a bit and folk forget and leave doors open. Fine if the car has a time out, not so fine if it doesn't. I usually google before jump starting, or looking at the connection process on the bag the jump battery pack is in - I never 'remember' as I do it so infrequently.
sneak up behind it and give it a good jump scare.
sorry
I remember, about 45 years ago, helping my brother replace a choke cable on his ancient Mini Cooper. I'm under the bonnet and he shouts "OK, just pull it", which I did.....Also DON'T let a metal spanner touch both battery terminals at the same time, 'cause that makes welding come alive 😎
....and dragged the cable straight across both battery terminals.
That was an interesting few moments with the bangs and fireworks 😂
Just don't cross terminals with a lipo... whoops
Jump Leads ? Peasants
We have two vehicles that probably need new batteries - if they are run regularly then they are fine - - but if left for a bit then can be tricky to start. We've got a good size NOCO to give them the required juice to get things going. Highly recommended
Good car engine running.
Red to dead
Red to good
Black to bad on a earth point, bare metal many cars have an earth point
Black to good
You may need to increase the revs a little on the good car, start the bad car after a couple of minutes.
Your last two are the wrong way round. The whole point of using a grounding point is that you don't risk a spark next to a battery.
(Also, is it just me that now has "Red Dead Redemption" as mnemonic for remembering where to start?)
Otherwise the negative terminal is fine providing you're careful.
It’s going to make a small spark regardless, and that’s the risk. That said, when you reconnect a battery after working on a car, it’s the same risk (maybe slightly less as the battery is likely to be in good condition/unstressed.
trying to push start a rented minibus round a car park and writing off the engine in the process.
Transit? Timing chain tensioner is hydraulic so when you shock it by bump starting it can jump the timing. We used to bump them all the time at work as the beacons would flatten the battery, loads of them were sluggish to start as they jumped a tooth!
flat car refused to start until I revved my car pretty hard
Car off battery 12.7v
Car idling, battery somewhere between 13 and 14v
Car revved slightly to 2000rpm, battery 14.4v
When using cheap and nasty jump leads with a mediocre earth on an engine lifting eye or similar, you could easily lose a few volts by the time it gets to the non runner. I don’t think revving it higher than 2000rpm will result in any more volts/currents as the alternator will be giving full output already.
The explosion thing is ancient rubbish,
I've seen it happen. You really do not want sparks next to a battery.
What am I missing?
I was going to say resistance down the jump leads and at the connection clamps, but Spooky beat me to it.
Also of you increase the current needed without adding more juice into the situation your voltage will drop won't it?
The explosion thing is ancient rubbish,
I've seen it happen. You really do not want sparks next to a battery.
If the battery is in the cabin, a gas vent tube should go to the outside. I guess you wouldn’t need to worry about sparks then.
Years ago on a tv program ’The Garage’ one of the mechanics disconnected a charger from a battery, without switching it of from the wall first. It went pop in his face, didn’t look staged.
If the battery is in the cabin, a gas vent tube should go to the outside. I guess you wouldn’t need to worry about sparks then.
Yes, but to connect a jumper cable to the battery, you need to open the battery compartment, which is where the hydrogen gas will potentially be.
On mine certainly, where the battery is in the rear hatch area, you pull one of the two vent plugs out of the side of the battery, push in a hose that goes to outside, via a small reservoir through a boot floor grommet, allowing gas to vent outside.
It is really old but my understanding is that hasn’t changed on modern cars with batteries in the passenger cabins.
