Abel's set up is similar in concept to my set up, but executed 100x better.

My schematic here 

http://shufti.wordpress.com/2013/06/24/vanagon-auxiliary-fuse-panel-schematic-update/

Since I wrote that post I have changed charger to a promariner, and added a solar charge controller.

I also have the voltage sense wire for the blue seas ACR connected to the auxiliary battery. That means that when the on board charger or the solar panel is supplying power, the ACR will connect the aux battery to the starting battery when the aux battery reaches a user defined setpoint voltage, I think I have mine set at something around 13V.

I also have to emphasize that you should find out from either the battery case or the manufacturers published data, the specific charging data for your auxiliary battery. 

In the winter, because if my driving habits and the lack of sun here, I plug in the on board charger at least once a week.

Alistair

> On Jan 13, 2015, at 6:39 AM, Abel Longoria <houstonphotog@GMAIL.COM> wrote:
> 
> here you can see what I'm talking about... where I can easily see the
> status of the charger...
> 
> http://dasmotoclub.com/wp-content/uploads/2015/01/auxbattery4.jpg
> 
> you can also see my Blue Sea emergency battery disconnect switches are
> easily accessible as well.
> 
> Abel.