For now I am going to use a small car battery to power the car's 12V system ... With a DC-DC converter to recharge this battery off the main pack (kind of like an alternator).
I am going to try and mount both the battery and the DC-DC converter in the standard battery position.
The first problem I had to face was that the DC-DC converter closely resembles a computer power supply. So the last thing I wanted was for dirt or water to be sucked through the unit.
My first idea was to buy an airtight food container and mount the DC-DC converter (and a few other things) inside ... Here is the container I picked up from K-Mart ... It is slightly larger than the DC-DC converter.Then:
I mounted the DC-DC on one side leaving an airgap below
I drilled out another side of the container for air intake and made a foam filter
I installed a 12V extraction fan on the lid
I installed the 50A shunt for the low voltage ammeter
I installed 2x 12V relays with their own fuses (for the power steering pump and vacuum pump)
I installed a 40A DC circuit breaker for all the cars remaining 12V power.Basically what this unit does is the car battery 12V positive power goes in one end ... runs through the shunt ... splits in 3 (the 3 large bolts on top) for the power steering, vacuum brake booster and remainder of the car. All while keeping my DC-DC converter and relays away from any dirt under the bonnet.