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BytheCmpFire · 05-22-2023, 08:22 PM

I have a 12V refrigerator in my 2021 Cougar Half-Ton, with 2 lead-acid chassis batteries, and the InCommand system. It is not very boondock-capable electrically. So I installed 2 200 watt solar panels on the roof, and an MPPT Solar charge controller. But rather than connecting this solar setup to the chassis batteries, I put 2 100AH Lithium batteries in the pass-through and connected the MPPT Solar charger to these batteries. I then installed a Dc to DC charger, which charges my chassis batteries and, effectively, the whole chassis 12V system. Does that makes sense to you? I didn't have to replace the converter charger, or alter my chassis 12V/110 system at all. I have a Victron 30AMP battery charger that I can plug in and fully charge the Lithium batteries if necessary. Am I missing something or is this not a good solution for a modular off-grid upgrade?

Captain8 · 05-22-2023, 09:21 PM

Why not just remove the lead acid batteries? I'm assuming your solar setup is 12v so running a 12v to 12v charger just seems like a waste, what's the efficiency of your charger?

If I were you I would just run everything off lithium then keep the lead acid topped off and unplugged. Maybe a trickle charger on it. Then use that DC to DC charger to drain your lead acid and charge the lithium when it gets low, or just have a switch to couple both battery banks together if ever needed.... until you just replace with more lithium.

Persistent · 05-23-2023, 07:55 AM

As far as I can see, the system should work just fine. The B to B converter is a little inefficient, but the lead acid and Li will not work together without it.

Solar: (2*200w) / 12v = 32a given approximately 6 hours of collection that is 200 amp hours per sunny day.

You can dry camp indefinitely if you don't use more than 200 amp hours per day. That assumes every day is a sunny day.

Try it and see how it works.

BytheCmpFire · 05-23-2023, 10:54 AM

Quote:

Originally Posted by Captain8

Why not just remove the lead acid batteries? I'm assuming your solar setup is 12v so running a 12v to 12v charger just seems like a waste, what's the efficiency of your charger?

If I were you I would just run everything off lithium then keep the lead acid topped off and unplugged. Maybe a trickle charger on it. Then use that DC to DC charger to drain your lead acid and charge the lithium when it gets low, or just have a switch to couple both battery banks together if ever needed.... until you just replace with more lithium.

The solar panels are 24V, but the MPPT I assume takes care of converting this to my 12V system? Regards switching the chassis batteries to Lithium, my thought was that with the Lithium providing constant charge via DC to DC, the lead acid batteries would remain in optimum condition, whereas if the lead acid is the feeder batteries, I would have to vigilant about the below-50% state of charge.

BytheCmpFire · 05-23-2023, 11:04 AM

Quote:

Originally Posted by Persistent

As far as I can see, the system should work just fine. The B to B converter is a little inefficient, but the lead acid and Li will not work together without it.

Solar: (2*200w) / 12v = 32a given approximately 6 hours of collection that is 200 amp hours per sunny day.

You can dry camp indefinitely if you don't use more than 200 amp hours per day. That assumes every day is a sunny day.

Try it and see how it works.

I have the Victron 12/12 30 AMP DC to DC charger, which touts a 94% efficiency...I'm guessing that's pretty good?

Thanks for the well-wishes, and happy camping to you!