12 replies to this topic

[Noah]

Wen't to jump start the mini today, First off I had to orchestrate cars and a mini with 4 flat tyres, because Issigonis didn't bother to put a suitable earthing point in the boot. Or at least one that I could think off.

The battery wasn't awfully flat because the hazzards we're flashing normally etc. But when the Honda (Power Source car was on) Positive to Positive, Negative to the brake servo, (Don't know if this is right, but it seemed logical to me, earthing, metal etc) It didn't start? Some one want to enlighten me? Do I need to pop down to halfrauds by a battery charged and leave it attached for a few hours?

Thanks for the advice.

PS, I've never jumped a mini before, it was a bit confusing because of the whole battery at the back and the earthing point at the front, the only other earthing point I could get to was the top of the gearbox.

Noah

[Cooperman]

The Mini battery has a positive & negative post. Just jump to those from the doner battery. In a Mini there is even a negative strap from battery neg post to boot floor.

[gwatkins15]

I put positive to positive, negative to negative on the batteries. The car its jumped to should be earthed correctly, so mine usually starts like that. I've had recent battery troubles and sometimes its so flat it wont jump, but its fine when the battery has been charged and then connected. Always useful to have a battery charger! Probably best to make a new battery earth cable as well, halfrauds do a long cable that you can cut in half and use for £5 which isnt too bad.

Just read above, agreed!

Edited by gwatkins15, 22 September 2012 - 07:07 PM.

[Noah]

The Mini battery has a positive & negative post. Just jump to those from the doner battery. In a Mini there is even a negative strap from battery neg post to boot floor.

Okay thanks, Will give it another go. I "earthed" it because thats what you're meant to do on "modern" cars. for example in Dads mercedes you go positive to positive and negative on the powered battery to well I tend to use the crank case.

[Noah]

I put positive to positive, negative to negative on the batteries. The car its jumped to should be earthed correctly, so mine usually starts like that. I've had recent battery troubles and sometimes its so flat it wont jump, but its fine when the battery has been charged and then connected. Always useful to have a battery charger! Probably best to make a new battery earth cable as well, halfrauds do a long cable that you can cut in half and use for £5 which isnt too bad.

Just read above, agreed!

The cable is the original but I do have a battery terminal and cable cleaner thing that just takes the grott and contaminates of both, its a great tool for a £5.

[AVV IT]

Now I know all the best practice safety stuff about always connecting the negative jump lead to a separate earthing point ,and not the negative battery terminal itself, because it could create a short and all that. But....... in reality does anybody actually do that??

I've been jump starting cars (particularly minis) "the dangerous way" on a regular basis for the last twenty years or so and have never yet had a problem. I've seen mechanics, AA patrol men and other roadside recovery professionals do exactly the same thing too. Come to think about it I don't think I've ever seen anyone ever jump a car "the safe way", by using an earthing point, everyone always uses the negative battery terminal. I've only ever read about the "safe way" in manufacturers safety instructions.

Those with in depth electrical knowledge are free to shoot me down in health & safety flames by all means. I just don't think that "best jump starting practice" is actually common practice at all in the real word. Surely if connecting jump leads directly to the negative terminal was as dangerous as its made out to be, there would be fried & shorted out batteries throughout the land every winters morning??

Apologies if this is going a bit of topic by the way!!

Edited by AVV IT, 22 September 2012 - 07:16 PM.

[Noah]

Well this is what I thought, but as I read it online in a few places I thought, oh well better to be safe than sorry, but surely if the negative cable is connected first it shouldnt make a difference, just like when connecting up a battery?

Again, electrical wizz, shoot me down.

[gwatkins15]

But surely the charged battery you're jumping from should be earthed correctly in order to that battery be ok, so connecting negative to negative should still be ok as its earthed? My alternators knackered so I'm running by swapping batteries over all the time....

[Cooperman]

I've been going from battery to battery, +ve to +ve and -ve to -ve for over 50 years and it's always worked OK. In fact, it reduces power loss due to added resistance on the body to battery connection which would then happen twice over if not done this way.

[Noah]

Will give it another go tomorrow and let you know the results.

[Noah]

Well, It worked!

After a while, she burst into life, we done it in the rain so it was just to check if she would start, but as soon as I took the cables off, shut the boot got back in the car and pushed the choke in, she stalled

Oh well.

[mab01uk]

I also usually jump start older cars as described, (many modern cars also have a separate positive connection away from the battery under a red plastic flip up cover as the battery is often tucked away or in a plastic enclosure).
The reason for not using the negative terminal on the dead battery for jump leads was perhaps more important in the old days when most batteries leaked small amounts of acid and gas, which could turn into flammable gas around the battery. This gas could explode if the jumper cable clamp caused a spark just above the battery when connecting up........there are cases of people being badly hurt by an exploding battery and of cause battery acid is not good for your eyes or face.......

Less of a problem with modern sealed batteries with a vent pipe fitted to the outside world but worth knowing if you are in any doubt as to the battery condition with your head inside a Mini boot!

Note: If you jump start a modern car always check the handbook as some don't advise it at all and some require heater fan, headlamps, heated rear window to be switched on in the car to be jumped to absorb any sudden voltage spikes and prevent them damaging expensive body and engine/transmission electronic control modules.

Edited by mab01uk, 23 September 2012 - 06:23 PM.

[Noah]

Lol, I smartly connected up to the mini first, incase of incident. lol.