Re: How to: Relocate a Battery.
I hope you don't mind if i add a few things, i'm going to anyway.
Any cables that run through a bulkhead or any metal area, must have a grommet in the hole to provide insulation between the positive cable and the body of the car. The reason is simple, if it wears through the cable insulation you will short to earth and set fire to the car.
Using a standard lead acid battery inside a car is a disaster waiting to happen, even in the boot but if you do use one the battery needs to be boxed and vented to atmosphere and well secured. The boot does not vent in the way an engine bay does, obviously, it's a sealed compartment and will store fumes from a charging battery, this is very dangerous, even more so on a hatchback type of vehicle.The fumes from Sulphuric acid are both toxic and highly flammable.The terminals need covering and isolating from any possibility of anything stored in the boot from contacting them and shorting to earth or the negative terminal, which again is a potential disaster in the terms of fire risk.
I would also advise you to fit an in-line circuit breaker into the system, as near to the positive terminal as feasable, this will protect you in the event of a short circuit or overload.
If you really want to relocate a battery, use a dry cell option.
The picture below is of my own install, we have done many variations and there are obviously many options. This install does have an aluminium cover. The battery is secured via a large central stainless steel clamp which uses a bolt lock at the rear and the base of the clamp is bolted into the body of the car. This is a Yellow Top dry cell battery, there is no possibility of acid leakage in the event of an accident.
I'm not trying to preach here or say that this is the only way but if you have ever seen the downside of an acid spill inside a car as the result of an accident, you will know what i am referring to.
Do modifications thoroughly and correctly and always think through safety options.