And now for the big one. Over the past season, we started having a number of electrical problems. Basically, the batteries were holding less and less charge, to the point where we could barely go a day without full blazing sun or hours of driving without losing the voltage overnight to the point where we'd lose power to the fridge. The whole concept of "don't drain your batteries too far" is something we never followed, and given the kind of remote camping we do, I don't see how you could do that. It's not usually a good option to lose your perishable food. So guess what? We killed our AGMs in just over 2 years.
It got so bad that the voltage would get so low (~10.5V - now that's
dead) that the (terrible) battery separator that FWC installs wouldn't even let us charge the batteries off the alternator because the house side was too low. There is no override switch, which I think is a bit of an oversight.
So my project over the past few weeks has been to retrofit the system for LiFePO4 batteries. Much thanks to the folks at Batteborn for helping me think through this project. As many of you probably have already figured out, these batteries are
not a "drop-in replacement". At least, not if you really want to maximize the benefit of your brand new $2k batteries.
My plan was to replace the two AGM 75 amp hour group-24 batteries with two BattleBorn 100Ah LiFePO4 GC2 (golf-cart form factor) batteries.
In order to maximize the solar system, switched out the Zamp ZS 30A with a Victron MPPT solar charge controller. I also installed a switch that would let me pick which solar panel I was drawing from: Roof, external rear plug, or both combined. I did this because I think the system doesn't perform well when one panel is in full sun and the other is in full shade, so I wanted to be able to select panels.
The battleborn folks recommended that instead of a simple battery separator or ACR, that I install a Battery to Battery charger to charge the batteries from the truck's alternator or from shore power. This was to prevent the LiFePO4 batteries from drawing too much current into themselves too quickly, which apparently shortens their life span.
And lastly I wanted to install a modern power monitor so I could see what was really going on with my system and not just rely on voltage readouts, so I installed a Victron BMV 712.
Here is the diagram of the final system I put together: