Dual Battery System (cont')

	Now for some of the wiring details. I found that the stock alternator did not have any connections directly to the stock battery. Instead there are two leads that are routed to the black plastic fuse-box which is mounted behind the OEM battery. One of these leads is actually a bundle of small wires that clips into the fuse box via a plastic pig-tail harness connector. The other lead is a heavier gauge wire that snakes up inside of the box. Then there is a wire that leaves the box, and splits into two cables. One goes to the starter and the other goes to the OEM battery positive connection. All I had to do here was extend the cable that goes to the positive battery terminal.
	Here is a basic diagram of how the system is wired (minus the sensing lines which go from the isolator to the controller). The only alterations that I had to make to the factory wiring was to extend the cable from the fuse box to the starting battery, extend the ground cable from the starting battery, and add a cable from the starting battery (positive) to the Pathmaker solenoid/isolator. All of the other wires and cable were add-ons, independent of the factory wiring harness. The sensing wires (not shown) connect from the solenoid/isolator to the control panel in the cab, and also go to ground.
This photo just shows where I routed the ground cables for both batteries. I decided to retain the OEM battery grounding bolt on the driver-side of the engine block, so I routed a new negative cable from the starting battery, around the front of the engine, and to the bolt. I routed the negative cable from the auxiliary battery similar to the stock cable configuration, where it meets up with the other negative cable and is attached to the same ground bolt.

As of the time this article was written, I have been using this system for almost two years. The only problem I have had is that the original yellow-top battery that I bought (via an Optima reseller on eBay) was a defective unit. Optima provided a replacement at no charge and everything has worked flawlessly since then. The Optima is working well, and the tough case really saved my hide on a trip to Mexico in 2003. The battery bracket worked it's way loose and wedged against the alternator bracket and fan shroud (vibration does amazing things! I have since used loc-tite on the bolt threads). The bracket wore a deep gouge into the case, but the case never broke! A standard battery case would have been disastrous in this situation.