National Luna Dual Battery System

Another modifications complete. Today I finished the dual battery system install in our new Toyota FJ Cruiser. For this build I chose to go with the National Luna Dual Battery system.

“The National Luna Intelligent Split Charging System allows you to maintain two or more batteries in your vehicle. The Intelligent Solenoid manages the charging of both of them when the vehicle is running, and isolates them when the vehicle is off. It is all automatic. You can monitor the status of the batteries, and manually override the connection from the Dual Battery Controller.”

The controller monitors the charge level of both batteries and provides alarms for low voltage and faults. The controller also provides a manual function to connect the batteries.

Charge Controller

The charge controller is mounted on the left inner fender. Both battery circuits are protected with 100 amp circuit breakers which also allow the battery to be isolated from the system. For this install I moved the small relay box that is attached to the left fender.

Circuit Protection

The charge controller is mounted on the dash panel in front of the passenger  seat.

Charge Controller

The system is wired with 0 gauge wire to reduce voltage loss in the charge circuit.


  • 0 Gauge wire: $35.00
  • Circuit Breakers: $24.00 each
  • Dual Battery System:  $145.00
  • System Controller: $90.00

Time to install: 6.5 hours



Tomas has lived in Colorado since age 5. Having grown up on the Western Slope of Colorado lots of time was spent in the Desert Southwest. Tomas' father introduced him to the love of 4 wheeling at an early age in the high mountains around Aspen, Colorado. While an avid Mountain Biker, Tomas and his Family enjoy adventures in the mountains and desert in the remote locations that can only be reached by 4wd. Day hikes are always a must when on the family trips. While enjoying outdoor activities he wants to share his love as a certified 4wd trainer and ski instructor. Tomas also enjoys caving and cave exploration. Tomas currently resides in Colorado Springs. 

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