Jump leads -- a cautionary tale

[news]

A few weeks ago I returned from holiday to find the car battery was totally flat. The only neighbour at home who might have helped start the car didn't have any jump leads, and neither did I, so I had to call in Homestart to get the car going.

Determined not to get into that situation again, I bought a pair of jump leads. Magnificent specimens, heavy cables, large crocodile clips surrounded in thick insulating plastic to prevent accidental short circuits.

Then, a few days ago, I came across an old gent in a car park, trying to start his car. As the car was a Rover, I felt sorry for him, and said I could give him a jump start. I positioned my car alongside his, and then got the brand new jump leads from the boot.

Major problem. The insulating plastic around the clips was so thick that it was totally impossible to attach them to the battery terminals in either car!

Half an hour with a hacksaw was needed to remove the plastic at the open ends of the clips, and now it's possible to attach them to the battery.

So if you have jump leads and have never tried them out, you know what you have to do.

[andrew]

Last time I helped someone out in such a situation, it was at work. I connected up my end, and he had the other ends to connect up his end. Big flash and crackle before I yanked a lead off. Well, he connected them round the wrong way. Was just thinking to myself that I should have done it and not trusted it to anyone else, when it dawned on me that he is the engineer who designs the high power (like 5V @ 1000W) supplies for the minicomputers we manufactured.

Fortunately, no damage done.

[Peter Taylor]

You still need someone kind enough to help you out. I remember coming back to Heathrow from Glasgow one evening to find I'd left my headlights on all day. I had a nice pair of leads with me, but not one person I asked had the kindness to help me. 'Twas a Triumph Dolomite. Maybe if I'd had a Rover......

Peter

[Jonathan Pearson]

.... or you lived up north! Jon

[Michael Chare]

With all the modern electronics in cars nowdays, I would be wary of using jump leads, but I do still carry an old pair!

[dennis]

Have you ever seen a car electronics damaged by using jumper leads? What would be the failure mechanism?

[Dave Plowman (News)]

The hand book of my car actually gives instructions on jump starting and provides terminals under the bonnet as the battery is in the boot.

[Doctor Drivel]

That's called crank handle.

[Dave Plowman (News)]

Like your 'name', John?

[Doctor Drivel]

My name is not handle.

[John Schmitt]

We all know that. It rhymes with the island of Sri Lanka.

John Schmitt

[Doctor Drivel]

Randolph, my name does not rhyme with Ceylon. Now your old name rhymed with S**t. Just as well you changed it.

[Nick]

not counting the ones I've missed....

Nick

[Doctor Drivel]

Randolph is a great admirer of mine.

[Hamie]

Same as mine. There's a dirty great +ve terminal on top of the engine under a plastic cover, and a (Brass looking) bolt on the front right suspension bolts for the -ve.

Although always connect last, and remove the +ve terminal first when it's started.

H

[Matt]

NO NO NO

Always connect the earthed connection last and remove first

Also never complete the connection in the vicinity of the battery i.e don't ever use the -ve battery terminal

[Bob Eager]

If you connect the earthed connection first...and then drop/brush the other lead against the body of the car.....

At least.

[Aidan]

Hydrogen and Oxygen. Yeah!

The battery can dry out leaving a empty space to fill up with hydrogen & oxygen, an explosive mixture.

A long time ago I blew such a battery up, left a spanner on it while turning the engine over. Big bang.

BLOODY HUGE BANG!

I was left with the bottom 2 inches of the battery casing containing a steaming puddle of acid and the remnants of the plates dangling on the connections. The only reason I didn't get a hot shower of acid and plastic shrapnel was that I was in the car & the bonnet was up. It was a "sealed for life" battery so I hadn't been able to check the electrolyte level. Not much acid spillage, other than droplets; there hadn't been much acid in it.

I repeat the embarrassing story only in hope of preventing anyone else getting blinded or killed by an exploding battery. The final connection is liable to cause a spark and so is to the chassis or engine and a loooooooooooong way away from the battery.

Treat with utmost caution. Be very afraid.

[Matt]

Because the first wire you connect is NOT a problem (unless the bodies are touching) You could drop the clips onto the body or anywhere and not cause a "flash" Then when you connect the 2nd wire, at the "good vehicle" end then its still a relatively safe situation as you can easily connect to the "flat battery vehicle" preferably on an earth strap well away from the battery terminals as if a spark occurs it will be away from explosive hydrogen that may be around the battery (its a slim chance)

Do it the other way round, earth first and you always have a +ve terminal to connect last and usually this can only be done at the battery, drop the jump lead in the engine bay of the "flat battery vehicle" and you may get a big bang and a screwed up electrical system on the "good vehicle" also as you connect to the "flat battery vehicle" you might get a spark and explode the hydrogen again.

Of course if you've done it loads of times you connect both wires to the good battery, walk to the flat one and connect the +ve one a second or two before you do the -ve one and all is well .......until the day you get distracted, put the clips on the floor, then there is a spark and the leads start smoking and glowing, the good vehicle revs drop and the alternator blows, the battery explodes and showers everyone with acid.

[Andy Champ]

I've often heard this said. Why?

Hydrogen?

Andy