Help wiring Blue Seas Add a Battery kit

[jeepskinc]

Okay, so I am not experienced with electrical wiring but thought I would give a try at adding a "house" battery to my 2007 Outback. I'm looking at using the Blue Seas Add a Battery kit which comes with a manual switch and ACR. I have been going through threads on this forum and many others and I am not clear on gauge of wiring I need to be using. On the house side I will be running a 400 W (30 amp draw) and 800 W (60 amp draw) AMPS. The 400 W amp is original equipment is currently wired with 10 wwg wires. On the motor side I have 2/0 positive and negative cables currently attached to the starting battery. I plan to run the positive cable from motor to the Blue Seas manual switch using the existing 2/0 cable. Question I have is what gauge should I be using from the switch to the startup battery and from the startup battery to the ACR. I'm thinking a 2 or 4 gauge cable for this. For that matter, I'm thinking 2 or 4 gauge for all the new wiring with only the amp to positive bus being something smaller gauge (e.g. 10 awg). My concern is that Moomba used a 2/0 from the motor to the startup battery. Am I going to have a problem using a 2 or 4 awg cable from the switch to the startup battery on the motor side? I have seen others using a 1/0 cable from their switch to the hose side fuse panel. Am I going to small with 2 or 4 awg cables?

[MLA]

I would certainly consult your blue sea dealer/installer for the specifics and a custom diagram. In general, cable gauge is based on the length of the circuit and the load it will potentially carry. Its better to go larger than smaller.

[jeepskinc]

After doing more research I was able to find the equations needed to select the proper cables for my application. Attached is the final schematic and couple pix of the install. This is on a 2008 Moomba Outback DD. I ended up connecting the house and amp cables directly to the stud on the switch eliminating the need for the positive bus. Negative leads from house and amps go to the negative post on the house battery with a 2/0 cable going from the house battery to the startup battery eliminating the negative bus. Startup battery continues to be cabled to the motor as originally provided by the manufacturer. With this setup, when the switch is in the ON position, house is isolated from startup system. But when engine is running and ACR detects low voltage on the house battery and charged battery on the startup side, the ACR will close and allow charging of the house battery. I'll likely install an additional control wire from the key switch to the ACR which will always close the ACR when engine is running and not rely on the low voltage detection to trigger charging. When switch is placed in EMERGENCY position, I have access to both batteries to run either side of the system with primary purpose is to use to start the motor should the startup battery not have enough juice.

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