Disconnecting Battery

[mike142sl]

OK, is it Neg off first or Pos off First ???

Then putting it back, is it Neg on First or Pos on First ???

[Disco-Ron]

My opinion.....

Neg OFF first, that way if the spanner touches earth when you're doing the positive it won;t arc......

and when refitting, positive first, for exactly the same reason!!

I'm prepared to be prooved wrong though....LOL!!

[Bishops Finger]

Neg off first

Pos on first

[Range Rover Blues]

Like RON says, the one that should be connected on it's own is the positive, same with jump leads, always isolate with the negative terminal.  It's exactly the opposite of where you fit a switch, hence the confusion.

[mike142sl]

Thanks guys, I got the first bit right so it's off to get the second bit right now. How am I going to remeber that? NOFPOF hang on that could go both ways.

[V8MoneyPit]

That applies to neg earth cars like yours anyway! Old pos earth cars would be the other way round. I always have to think carefully when jump starting the Grey Fergie. It's pos earth and being jumped by a neg earth car!

[Range Rover Blues]

That applies to neg earth cars like yours anyway! Old pos earth cars would be the other way round. I always have to think carefully when jump starting the Grey Fergie. It's pos earth and being jumped by a neg earth car!

Hmm, I'm sure there is way round that but I bet it made you Very careful ;)

[hobbit]

Another little thing there is on jump starting a vehicle, his connect dead battery to live, ie, connect up each lead from the dead battery to the live battery, and look properly to make sure of the polarity of the other vehicles battery, especially if you haven't used it before, sometimes what may look like pos may not be, check for the markings on the battery itself you are connecting form

It may sound obvious, but some of the vehicles I've had to start, sometimes you could make a mistake, too easily done, not worth the hassle and damage it can cause especially on modern cars

Even now with myself, my lightweight has a live feed drain, so I normally disconnect the offending item if I'm not using it for a day or two, and reconnect when starting, but sometimes I forget, then out come the leads, although I do this on a regular basis on the same vehicles, I still have a second look out of force of habit to make sure I have the right lead going to the right connections, cold morning, tired eyes can = lovely sparks shower

Have fun :)

[muddyjames]

Neg off first

Pos on first

I was told positive off first then positive on last. That way it kills the whole vehicle being live and you always have a neutral back to the battery. If the neutral is off but positive is on then anything will find a way to earth through vehicle etc.

[freeagent]

neg off first, then neg on last.. that way you can't short out if you touch the bodywork with a spanner while touching the live side...

[Nick4X4]

I was told positive off first then positive on last. That way it kills the whole vehicle being live and you always have a neutral back to the battery. If the neutral is off but positive is on then anything will find a way to earth through vehicle etc.

you was told wrong then

[mike142sl]

Neg off first

Pos on first

If the neutral is off but positive is on then anything will find a way to earth through vehicle etc.

How would this work?, surely there needs to be a connection through the battery and if one is NOT connected there can't be a current.

[karlo]

You always remove Neg - first then Pos +.

You reconnect Pos + first then Neg -.


This prevents any chance of the Pos + lead touching an earth point on the vehicle and shorting out.

[Disco-Ron]

My opinion.....

Neg OFF first, that way if the spanner touches earth when you're doing the positive it won;t arc......

and when refitting, positive first, for exactly the same reason!!

I'm prepared to be prooved wrong though....LOL!!

I don;t understand why people don;t get it, the same answer has been posted all the way down the page.......

[muddyjames]

You always remove Neg - first then Pos +.

You reconnect Pos + first then Neg -.


This prevents any chance of the Pos + lead touching an earth point on the vehicle and shorting out.

cant get my head around it at all I a affraid. same with accounts, I cant do them either! :lol:

[karlo]

OK, if you disconnect the positive + lead first from the battery and it touches something you will get sparks, bangs, fried electrics, risk of the battery exploding e.t.c. which is not good.

a bit like this:

http://uk.youtube.com/watch?v=LyY0JFhThfM