In the event the battery get's drained what is the proper jumper wire connection? The ground connection should be clipped to what grounding point in the boot?

 

Here you go:

 

What would be the problem in connecting the negative jump lead directly the the discharged battery ?

 

It's all about minimizing Risk. Risk of accidental short circuit. Batteries produce hydrogen gas, risk of explosion from spark negative terminal while connecting.

These unlikely possibilities are the only reasons I can think of. I almost commented on how " highly" unlikely these are, then I remembered that one time a car I was working on almost rolled off the jack while I was changing a flat. It woke me up fast. Some things are just not worth taking a chance with.

Anyone else got any other reasons I missed?

John

 

(Edit: had not seen Jonken's post when I posted this. Mine is sort of redundant.)

In a word, sparks. When making -- and even more so, breaking -- the last of the four jumper connections you're likely to get some. With traditional batteries, hydrogen is being burped out during charging and hydrogen + sparks = trouble. So we want that last connection made at a spot not near a battery.

Not so much of an issue with AGM batteries, but better to follow the safest procedure.

 

Direct battery jumping connections can result in battery explosion and put you at extreme risk. The car being jumped should always have it's ground jumper wire attached to a grounding point somewhere on the vehicle frame/grounded bracket other then the negative battery post of that vehicle. The starter car battery cables are simply connected to the terminals, red positive to positive post / black to negative post but not the vehicle being jumped.

 

Thanks guys.
This should never happen in the boot of a Jag

 

very important, the explosion risk is bad enough in an enclosed area. the worse part is that caustic chemicals and debris can be propelled into delicate areas of your body such as the eyes. usually you are performing the jump start away from necessities such as water to flush the acid away. always keep a pair of protective glasses in the boot kit and use them when doing things such as this.

 

THANKS for this! A picture may be worth a thousand words, but a video is worth a thousand pictures. I'd never seen this oft-described phenomenon, and it is now indelibly imprinted on my brain.