electrical system quest

[rogerman]

What happens when you connect the + to the - and the - to the + on a battery? what damage does it do to the car? i know this sounds stupid in all but what fuses would blow if this was to happen?

[Tommy]

well, if you do it for more than like a split second, you risk blowing up the battery

Ive bridge the terminals before, not paying attention and dropping a screw driver or hitting it while undoing a terminal, you just get a big spark and a chunk on metal missing from your tool. doesnt seem like there is any serious damage with a quick tap, but i wouldnt do it more than that, or make it a habit.

[flex-appeal]

Like the man said, dont make it a habit - a quick tap is ok to see if the battery is dead.

In more technical terms what happens is this (i'll try not to get carried away with my explanation). Current flowing through a circuit is determined by volts/resistance - in a short circuit situation resistance is of course very very small, the voltage we know is 12V so therefore the current is 12 / Resistance . This ends up being a huge number and does damage somewhere if there are no fuses to blow etc.

For example, on a car battery if you short circuit it with a wire that has a resistance of 0.1 ohms (many wires could be even lower than that) then your current value is :

12/0.1 = 120 Amps

If there is no fuse then the wire will simply melt, burn, you can also start engine fires this way. Remember that this high value of current is only through the path with the low resistance , so your short circuit wire will melt but other car systems will probably be ok.

[rogerman]

alrite thanks for the replys guys i ended up blowin my Alternator,Efi and dome fuses replaced them and my truck was good to go

[nkhhh]

if i am not mistaken, the alternator would be the first to get burnt

[rogerman]

yup your correct and its the hardest god damn fuse to remove