i was watching motor week and they had a skit on jumping a car

on the good battery
attach the red cable to the pos and the black to the neg

on the dead battery
attach the red cable to the pos and the black to the frame or block BUT NEVER the the neg

they didnt say why but i always have done pos to pos and neg to neg

anyone ever hear of that?

 

Batteries produce a small amount of hydrogen gas as the liquid inside of them evaporates. Theoretically, if the battery has been sitting there dead for a while then the hydrogen could be dense enough to explode. Since the negative or ground on the dead car is the last to be connected, there is going to be a spark. You don't want that spark to come in contact with hydrogen and go boom.

Before any hydrogen is produced the battery has to have been setting long enough for the liquid inside it to start evaporating. Were talking weeks if not months and not over-night or a weekend. I have always just put it on the negative post of the dead car without thinking. But its a good practice not to because of the possibility of the BOOM.

 

Actually when the battery recharges hydrogen gas is created. If you've ever had a battery charger fail and stay on.... holy ****! Shop smelled like rotten eggs for a whole day.

Yes, he's right, it's for not wanting the spark to happen near the battery, they tought us this at school as well.

 

Last connection to body ground or the engine block is the way it's recommended in all the owner's manuals I've come in contact on any car I owned.

 

The main reason is because the engine block provides a MUCH better ground than the negative terminal. the body is usually a dumb place to put it because it is typically aluminum.

 

unfortunately, ive never had any luck jumping a car the correct way. as soon as i jump it directly on the battery, it starts. dont know y

 

I do cause ur a num num

 

The body is aluminum?

 

how would the block provide a better ground then the actual ground?

aluminum?


i think ill take the answer : Actually when the battery recharges hydrogen gas is created.

 

oops wasnt thinging....you know what i ment.

 

I'm fairly certain the last two times I jumped a car (my car was the live battery, red top FTW!) I did the opposite of this and connected the black to my block.

What you are saying here is i've been doing it backwards?

Worked both times btw. The explanation I received was to prevent computer damage.... Guess there was a better reason.

 

I always go pos to pos, neg to neg, hooking up the good battery last. I was taught this at the technical college i went to.
A dead battery could have boiled off enough electrolyte and left hydrogen gas behind that an internal spark would cause the battery to explode. You don't want to stand over a dead battery while making the final connection regardless of whether its on the terminal or block.
My instructor claims to have seen this, and I believe him.
Rapidly discharging batteries make hydrogen as well as charging batteries.

 

right i usually connect the bad battery first and then the good one

 

Red on Red and Black on Black. Let's keep it simple. Electrons aren't magic.

 

Good to know , living in canada there always someone looking for a boost in the winter!