Jumping a car

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It's more important with older batteries (the ones you top up with DI water) which can emit hydrogen. If there's a spark when the leads are removed it can explode the battery and cause injury.

I've jumped a few cars with modern sealed batteries and have connected to the neg terminal with no ill effects. I wouldn't know where to clamp the neg lead otherwise!

HBS x

Norman_Castle

EssexExile wrote: »

Never heard that one, why?

I believe its to bypass possible losses from a weak engine earth strap.

colino

You don't connect to a dead battery negative terminal simply because it will draw most of the power trying to recharge instead of it getting to the starter and ignition circuits where you want the power.

facade

I try to connect the engine blocks together, as some manufacturers have no idea that black=negative.

If you connect the engine blocks together then connect only the positive lead to the positive terminals, the worst that can happen is a blinding spark, rather than a dead alternator or ecu.

It can also help a little with voltage drop around earth braids, but that isn't the reason.

EdGasket

Don't do it; you risk frying the electronics on one or both cars. Either get a new battery if you are sure it is the battery and not the alternator or else remove the battery/disconnect one lead and charge it with a battery charger. It is the only safe way.

See:
http://www.dailyrecord.co.uk/authors/the-judge/driver-vents-fury-after-simple-1558512

B6 Quattro blown ECU jump starting another car:
http://forum.a8parts.co.uk/showthread.php?t=3980

Damage ecu posts 16 and 21:
http://www.audizine.com/forum/showthread.php/295951-Jump-starting-an-Audi

Blown air bag module:
http://www.vwaudiforum.co.uk/forum/showthread.php?150126-Brake-and-Air-Bag-Warning-lights-after-jump-starting

Blown alternator + ecu?:
http://www.vwaudiforum.co.uk/forum/showthread.php?51896-Damaged-Ecu-Due-To-Jump-Leads-Spike-Golf-Mk4

RMS2

Zola. wrote: »

I plan to jump it when I get back.

I'm not sure how this is going to help. It sounds somewhat sexually deviant and may involve an officer of the law turning up.


However, 'jump starting' a car is a good way to get a car going that has a flat battery.

robotrobo

jack_pott wrote: »

jumping a car.

fender bender!.

---lee---

colino wrote: »

You don't connect to a dead battery negative terminal simply because it will draw most of the power trying to recharge instead of it getting to the starter and ignition circuits where you want the power.

Electricity does not work like that. The battery is still connected to the circuit and will draw as much power as it can once the circuit is made. As already stated the reason is to keep sparks away from the battery.

BeenThroughItAll

EdGasket wrote: »

Don't do it; you risk frying the electronics on one or both cars. Either get a new battery if you are sure it is the battery and not the alternator or else remove the battery/disconnect one lead and charge it with a battery charger. It is the only safe way.

See:
http://www.dailyrecord.co.uk/authors/the-judge/driver-vents-fury-after-simple-1558512

B6 Quattro blown ECU jump starting another car:
http://forum.a8parts.co.uk/showthread.php?t=3980

Damage ecu posts 16 and 21:
http://www.audizine.com/forum/showthread.php/295951-Jump-starting-an-Audi

Blown air bag module:
http://www.vwaudiforum.co.uk/forum/showthread.php?150126-Brake-and-Air-Bag-Warning-lights-after-jump-starting

Blown alternator + ecu?:
http://www.vwaudiforum.co.uk/forum/showthread.php?51896-Damaged-Ecu-Due-To-Jump-Leads-Spike-Golf-Mk4

For every example of a damaged ECU I raise you hundreds of cars successfully jump started every day.

RMS2

Well, you could use the good olde fashioned way, like we used to do when we were younger and battery life was counted in hours, or you could sit and watch a Fiat rust during the two minute warning.


That was to get a couple of mates to push and bump start it (notice I didn't say to bump or hump the vehicle). The trick was to, get ready to stand up and not fall flat on your face as the vehicle coughed and spluttered and then pulled away in 2nd gear rather sharpish.