It was my initial way to do it, but I wasn't 100% sure the wiring I've done would work and not explode. I have a poor history when it comes to wiring!

The other reason is that I won't be using the cut off all the time, which means it's more likely to be left connected than not, as most of the time it's parked fairly securely.

Merryck said:

It was my initial way to do it, but I wasn't 100% sure the wiring I've done would work and not explode. I have a poor history when it comes to wiring!

The other reason is that I won't be using the cut off all the time, which means it's more likely to be left connected than not, as most of the time it's parked fairly securely.

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The battery clamp is to secure the battery in the event of an accident ...

If in doubt of your wiring get an auto electrician to check it ...

Merryck said:

So I bought myself a nice big 40 amp relay and a switch. I'd like to wire them into a battery cut off to try and deter any would-be thieves.

I was going to separate the battery cable between the positive terminal and the starter somewhere, would this be the right point to break the circuit?

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Poooft, that's the smoke and melted plastic when you try and start it...

It's simple enough to work out it properly with P = I x V. Bosch starters are about 2.2Kw so at 12V that's 183A, however it not as easy as that, take a cold day, a longer crank, battery voltage falls off and before you know it that could shoot up to 244A. Then there are issues such as the starter getting lazy and drawing more power.

I would say to be safe 300A minimum SUSTAINED, but personally I would go even higher and probably use a marine switch. That's just me though.

Also, you may want to consider a small bypass line with a fuse in it to continue operating your clock etc if you have one.

Cheers for that, certainly good info for those wanting to do it. I went with a cot off for the fuel pump in the end, the other advantage being that they can still crank it but it won't start, making it look like it's just a ****e Land Rover as opposed to intentionally disabled.