Hi guys,

Just a quickie...
Does it make a lot of difference whether I hook up a battery kill switch to the live or the earth connection?

Cheers
Andy

From an electricity point of view no. I have mine in the neg line.
But…?

Recent discusion
http://www.locostbuilders.co.uk/viewthread.php?tid=187588

[Edited on 23/3/14 by ReMan]

All the fia wiring diagrams suggest live.

Strange that FIA suggest the switch in the positive, Brisca F2 cars MUST have the cut out in the negative. The reason is because it is safer.

Lets take the example of the cut out in the positive wire. If there is a short to the chassis in the length of positive wire between the battery and the cut out then the battery will discharge quickly probably causing a fire and turning the switch will have no effect.

If the cut out is in the negative wire then a short in the negative wire will not result in the battery discharging. The result will be that the switch has no effect but it would not cause an emergency just be unable to prevent one. So the switch in the negative wire is safer. The only connection between the battery and the chassis should be this wire.

If you must put the cut out in the positive wire then keep the wire from the battery to the switch as short as possible to reduce the chance of a short to earth.

Of course road cars are different to competition cars in that they have items such as clocks and radios that need a constant feed so these items should be wired direct from the positive terminal of the battery with the appropriate fuse, and back to the negative terminal.

[Edited on 23/3/14 by scott h]

[Edited on 23/3/14 by scott h]

Correct on my Jedi it is switched negative, much better in my opinion

Always negative assuming negative earth.
Same goes for disconnecting batteries manually.

Better in the negative. That avoids a situation where the alternator keeps the volts up and the reg gets fried.