www.PaulDotTrip.com

My 72 westy didn't have a second battery, but I wanted one for camping with my 12v fridge, fans, interior lights etc. The BN4 heater had died, so I used the heater real-estate for a second battery. (didn't need a heater for a trip to Central America)

I've never owned a bus with factory dual batteries, so I cannot compare this solution to the factory solution. I am not concerned about appearances and decided this aftermarket solution would be best for me.

The solution below may help you, it may not. It has certainly worked for me the last 6 months driving 8,000 miles through Mexico and the 7 Central American countries. Since adding the 2nd battery I've never ran out of cranking power after camping for a couple of days. (those 12v fridges sure suck power!)

The separator is an automatic relay that normally keeps both batteries wired in parallel. However, when the voltage in the engine battery drops below a certain point, it disconnects the two batteries from each other.

This allows you to run devices hooked into the accessory battery until you drain the accessory battery. However, the engine battery will always have enough cranking power left. As soon as the engine is running, the alternator starts charging BOTH batteries as a single entity. This separator was very easy to install. I did not have to splice into any factory harnesses or mess around with the alternator or voltage regulator. The separator performs its job automatically.

The separator also has terminals for a "booster button" that you can mount on your dash. Even though I haven't used this feature yet, it's pretty cool.

For example, let's say you left the headlights on and it drained the engine battery (the separator would automatically disconnect the two batteries from each other). Now you have a fully charged accessory battery and a dead engine battery. How do you start the engine with a dead engine battery? Just press the "booster button" and give yourself a jump start! The booster button manually connects the two batteries together. Great for when the engine battery is low or you're in freezing weather etc. Alternatively, If you don't want to hook up the booster button you could always jump yourself with one (positive) jumper cable between the two batteries (the negatives are always connected to the frame).

I'm sure there are many separators on the market. As I recall the one I used costs around $70 (plus $60 for a deep cycle RV battery and box from Walmart). Vendor was Mobile Power Inc. of New Jersey. Phone 1-800-433-0781

Here's the battery separator mounted in the engine compartment. The heavy positive wires connect each battery to the separator. All "accessories" are connected via 12 gauge wire with inline fuse close to battery.	Here's how to hook up the battery separator.	The separator I used is model 1315 from Mobile Power Inc. of New Jersey. Phone 1-800-433-0781	Accessory power feed comes up through hole in spare tire well then alongside wall in rear seat area then along floor behind table. Make sure there is an inline fuse as close to the battery as possible.
I mounted a 12v silver socket behind the drivers seat. This power socket is ONLY connected to the accessory battery. I continued a powerline into the roof then into the rear cabin light assembly.	A radio shack SPDT (single pole, double throw) switch was added to the cabin light assembly. When it's flicked one way, the lights are working off of the accessory battery. Flicked the other way, lights are connected to the engine battery.