Ammeter with Auxiliary Battery

[rpmerf]

That diagram is VERY helpful! I was confusing how the factory setup was wired. I had removed the factory aux batt harness about 7 years ago. The second battery was in the bed, and I wasn't crazy about that setup. I wasn't sure how factory it was, and there were some other wires run also that certainly weren't factory.

I've attached an image of how I wired it. I thought I was basically replacing the relay with an isolator, and moving the alternator from the driver's side junction to the isolator, but I was wrong.

A bit of explanation on why I wired it this way. The isolator has 2 diodes, so each battery get charged by the alternator, but they are never directly connected together. I am using the isolator because I've always heard you do not want to directly connect the batteries as it can cause a large amp flow if they are unevenly charged. I've also heard it can under charge / overcharge from the alternator if they are not equal charge and capacity.

I like it wired this way, because if I leave my headlights on (or something on the in cig lighter, or a door not closed all the way, etc.), it will kill the driver's battery, but the passenger's side battery will remain fully charged, and be ready to start the truck.

Hope this all makes sense...

Given this, I think I will move the amp meter between the driver's side junction and the driver's side battery. This way I can see charging from the alt to the driver's side battery, and discharging from the driver's side battery into the fuse block and accessories.