National Luna Dual Battery System 

Great to hear! It's meant to be a simple system and it should work when you need it. Love to hear it.

You would need to hook the solar panel directly into the battery. If you wanted to charge both at once, you'd need to use the override feature on the controller and bridge the two batteries.

@@tacul9333 DO NOT connect a solar panel directly to a solar panel. You need a solar controller between the panel and your battery. The controller is essentially a funnel that dumbs down the voltage generated by panel to a voltage that the battery can safely accept. High output panels can put out close to 40v, you don't want to connect that to a 12v battery.

Connect the solar panel to a charge controller and connect the output from the charge controller directly to the battery you want to charge off solar. If you want to charge both batteries off solar panels, then get 2 panels and 2 controllers (one for each battery/panel). I've been running like this for 8 years on the same pair of batteries. Batteries always full when vehicle standing unused for a while. This National Luna system had been rock solid

I have this setup for my Xterra. Curious to know can this system charge a lithium battery. I’d like to get a 100ah lithium battery as my secondary.

We've noticed if the four pins in the controller get tweaked or make poor contact with the female contacts in the wiring, it can cause some bugs. Also, the sequence in which wiring gets connected is very important in this system. Most folks connect the ground and then the positive. This creates a tiny arc of electricity. This arc is enough to cause issues in the circuitry. This is why National Luna requires the positive cable to be connected first, then the negative. There is no arc in this sequence. More often than not, we see issues with this system after someone has done some work requiring cables to be disconnected, we've also had shops replace these for customers because the shop did not connect wiring correctly. Please note, if anyone is having issues, we have parts available and you're covered under a three year warranty.

Great question. The solenoid connects and disconnects based on voltage levels. A recently charge/energized battery can take some time to drop to resting voltage, unless there's a load on the aux battery immediately. This means, the car can be shut off but voltage doesn't drop to the disconnect threshold of 12.7v. Let's say a fridge is connected to the aux battery when the vehicle is shut off, the load on the battery will drop the voltage level of the two batteries faster than no load. In this case, this would cause the solenoid to disconnect more quickly. Generally they should disconnect within 20-30 minutes but it varies based on the batteries, solar connections, etc.

@@Equipt1 thank you for that reply helped me a lot