Battery Dangers.

["therealdmcvegas" <DMCVegas@xxxx>]

Not so fast! Correct grounding points on a car are far from foolish when 
jumpstarting a battery! I wanted to research this one first before I responded. 
The danger is this: When a battery charges, it will give off hydrogen gas, 
which is VERY explosive (the Hindenburg was inflated with it, and everyone 
has seen the old newsreel it it catching fire. Although a car battery will not be 
this severe). When you are jumpstaring a dead car, you are charging the 
battery, it will give off hydrogen gas (the weaker the charge, the more gas that 
will be given off). So the reason that you don't ground the connection to the 
dead battery is that you don't want any sparks to accidenty ignite the 
hydrogen gas. Sparks from when you connect the jumper cables, and if any 
grease is on top of the battery that may possibly allow an arc. And of course 
you don't want to simply attach the cable to anything else but a hoist point on 
the engine. Anything else you will risk damage to. It's basicly an arc wleder 
wich will ruin the paint, and will not give as clean of a ground connection (the 
epoxy coating on the chassis for instance is a pretty good insulator). And 
especially don't clamp the negative cable to a fuel line!

Now, as to why the negative cable must be connected to the live car, I don't 
honestly know. If I were to guess, I would say it would be to provide proper 
feedback to the alternator so it can give the correct output. A few hunderd 
amps to start another vehicle is a far cry from a slight dim when you turn 
normal accessories on. Or maybe it's so the battery can absorb electical 
spikes, I don't know.

Over all, I've seen a few methods on the internet written on how to connect the 
cables. But all of them list connecting the negative cable on the dead car to 
the engin last! As usual, here is a reference page:

http://www.popularmechanics.com/automotive/sub_care_sat/2000/9/
jumpstarting/

-Robert
vin 6585 "X"



--- In dmcnews@xxxx, "Phillips Jeff 1Lt AFCA/GCF" <jeff.phillips@xxxx> wrote:


> All this talk about where to connect jumper wires is foolish. Electrically there 
is no difference where you connect your ground jumper as the negative 
terminal of the batery (regardless of jumper or jumpie) is directly bolted to the 
engine block. Check it out for yourself. And as the hip bone is connected to 
the thigh bone, so is the engine block to the frame and etc. Granted if I was 
truely conserned that I had a bad gorund somewhere in my vehicle then I 
would try to connect as close to the battery terminals as possible when 
charging the battery, but as the car runs fine and I don't have electrical 
problems I always just use the post in the engine compartment and the largest 
piece of unpainted metal that my charger cable can reach.