National Luna Dual Battery Install

National Luna Dual Battery Install

Dual Battery Install Toyota FJ CruiserA dead battery as a result of the wrong setting at Overland Expo (twice) reinforced the need for a dual battery system in our TRD. While running LED lights and manually disconnecting items we don’t use every day worked ok, in reality any truck that may perform overland/camping duty will need an auxiliary battery eventually.

After attending Paul May’s overland electronics class at the Expo I was sold on the National Luna system. The fact that you don’t have to match batteries was one of the main selling points, but the easy to use controller and automated nature of the system are huge advantages over other systems. I called Equipt Expedition Outfitters and got a kit on the way.


It’s apparent from the packaging that National Luna has been doing this for a while. The kit is put together very simply, and the instructions while a little complicated, are easy to follow. There are many steps involved to properly install a dual batter kit, so if you’re not 100% comfortable with major electrical work, we recommend you have a professional shop do the install.


I was lucky enough to have Jim Akers from Tacoma Magazine, and the illustrious Tim Mitchell to help make this project a reality. Without their help I fear it would’ve taken days instead of the 4 or so hours on a sunny Sunday afternoon. The major issue with the install is that all the cables from the kit have to be cut to length, and finding enough room in the FJ can be difficult.

In addition to the intelligent solenoid from the National Luna kit, we installed a Blue Sea fuse block to handle all the accessories. I labeled all the wires from the original install to make it easy to setup the block. We also had to extend quite a few of the original wires since we moved to the other side of the engine bay. It’s important to use good soldered connections and heat shrink whenever possible with this type of install, so that took quite a bit of time.

We sourced an Odyssey Extreme series for the auxiliary battery. It’s heavy duty deep-cycle capability means it’ll hold a charge and take the abuse of all the accessories attached to it for years. For the main battery we used an Optima Red Top, it’s perfect for the primary job of starting in the cold Colorado winters. Together these two really are the perfect setup for our needs.

One great feature of the intelligent system is that it automatically switches to dual-charging 5 minutes after the truck is started. This allows the main battery to get charged up after starting. You can bypass this feature using the controller if needed. The controller also shows levels for each battery, and features a low battery alarm if either voltage drops too low. The intelligent solenoid also automatically uses the auxiliary battery for starting if the main drops too low, so you’re assured a start even on the coldest days.

An issue anyone with an early model FJC dual battery system has dealt with is where to mount your auxiliary battery. While we had a general idea during the install, there was no way to mount the Odyssey battery tray to the truck with my limited fabrication skills. Luckily I was able to drop the FJ off at Armorology here in Colorado Springs for a day and Jed fabricated an awesome custom mount. It’s now solid an won’t move an inch either on the road or on the trail. If you’re lucky enough to drive a 2010+ FJC, the right side of the truck is already setup for a battery, so mounting is much easier to accomplish.

So how does it work? Well, so far I’ve managed to leave my lights on & drain the Optima a little too much on one occasion. The system worked flawlessly and the FJ started right up. I’m very happy to see battery levels all the time, although I may have a drain on the main battery I have to track down. This system really provides great functionality and peace of mind. The first step in our Extreme Makeover: FJC project for 2013!


More Photos!

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