Correct way to disconnect battery?

[cmhj]

Originally Posted By: Pop_Rivit
Originally Posted By: HosteenJorje
Here is the answer. Put a wrench on the positive connection of a charged battery and let it touch a ground.I guarantee you will never ever do that again.


I've done that before on my Ford Ns without a single problem. In fact, when I remove the battery from one of them the positive cable is the first cable that I remove and I frequently touch the wrench to the hood without a single spark.

Want to guess why?


No need to guess. They were positive grounded.

 

[B320i]

Take negative off first is what I've always understood, this thread has clarified that you can't get a "zap" doing negative first.

But... What if your wrench / spanner (etc) touches the vehicle whilst undoing the positive on a typical negative-ground car. Won't that create a circuit?

 

[Jetronic]

the negative grounded car only exists as long as the negative terminal is connected. when disconnected, there's no circuit.

 

[Jetronic]

Originally Posted By: supton
Originally Posted By: Jetronic
Originally Posted By: eljefino
It takes 50 volts to break through your skin and give your body trouble.

However your tongue can feel 9 volts as it's more conductive. Give a 9V battery a lick and report back.

I can and have felt tingling from 24V....


Not surprised. Moisture content of skin and/or how much sweat (or other salts/metals) would impact how conductive you are.


I'm a good conductor

 

[supton]

Originally Posted By: B320i
Take negative off first is what I've always understood, this thread has clarified that you can't get a "zap" doing negative first.

But... What if your wrench / spanner (etc) touches the vehicle whilst undoing the positive on a typical negative-ground car. Won't that create a circuit?


Once one battery terminal is removed, the circuit is broken. No current can flow.

"Circuit" is Greek for "circle". Current flows in circles. If a continuous circle cannot be drawn, then current cannot flow. The battery cares not which terminal is removed first, as it opens the circle and breaks the circuit/circle.

You could make the rule "disconnect the terminal tied to chassis ground first" and that would cover both types of ground systems.

 

[ChiTDI]

The current is not the only danger.
Leaking sulfuric acid being trapped in a closed area can produce an unpleasant surprise when someone sparks a positive battery cable.

 

[exranger06]

Originally Posted By: ChiTDI
The current is not the only danger.
Leaking sulfuric acid being trapped in a closed area can produce an unpleasant surprise when someone sparks a positive battery cable.

Sulfuric acid is not flammable. The danger is batteries generate hydrogen gas when charging, which is highly flammable.

 

[Silverado12]

Originally Posted By: eljefino
It takes 50 volts to break through your skin and give your body trouble.

However your tongue can feel 9 volts as it's more conductive. Give a 9V battery a lick and report back.

Ouch!

 

[ChiTDI]

Originally Posted By: exranger06
Originally Posted By: ChiTDI
The current is not the only danger.
Leaking sulfuric acid being trapped in a closed area can produce an unpleasant surprise when someone sparks a positive battery cable.

Sulfuric acid is not flammable. The danger is batteries generate hydrogen gas when charging, which is highly flammable.


That makes sense.