36v/12v lifepo4 solar charging options?

[Tom Morrissette]

Hi all. My first post here. I'm venturing into the diy battery/solar realm with a system for a new truck camper (Lance 850), and a boat (23' World Cat with twin 2005 Honda 150hp outboards).

The camper comes pre-wired for up to two solar panels and two battery boxes (I have to check what kind of charging system it has factory installed). The boat takes two 12v cranking batteries and one deep cell house battery (all agm currently), that charge from the alternators and a Noco genius three bank shore power charger (will have to check model).

My plan is to buy 20, EVE 280ah, 3.2v lifepo4 cells. I'll build two 12v's for the camper (8 cells), and three more for the boat (12 cells). For now I plan to keep the agm's I have, and use the three lifepo4's (wired in series) for a 36v trolling motor (When the agm's are nearer the end of their life, I'd like to replace them with diy lifepo4's as well).

I think I have all the information and resources I need for the batteries (although all advice is welcome!), but my big question is: what is the best/most efficient way to configure solar to charge both the boat's 36v bank, and the camper's 12v bank?

I'd probably like to mount at least two 100w panels on the camper. I'd like to use four 100w panels total, but I'm not sure about space (especially on the boat). Assuming I can figure the space out and decide to build a 400w solar charging system, is there a good blueprint could I use, and what components should I consider in order to charge both the boat's 36v bank, and the camper's 12v bank?

Most likely, I'll keep the whole solar system with the camper, and plug the boat to it when it's on it's trailer, although I'm open to having separate systems, with probably just one panel on the boat, if it doesn't add too much cost (but it would be very rare, if ever, that I'd need more than 280ah on a boat trip). Is my best option to just use an inverter to run a designated 36v charger for the boat?

Thanks for anyone patience enough to read through all this! Look forward to your replies.

 

[circus]

I'd like to share how I solved the space for PV problem. At least when parked. 360w on the road, 720w parked. By the way, thanks Will for the blocking diode tip. Rained all day Thursday and I still was getting over 200W. The shade is nice too.
Wouldn't the systems almost have to be separate considering the voltages?

 

[Tom Morrissette]

I'd like to share how I solved the space for PV problem. At least when parked. 360w on the road, 720w parked. By the way, thanks Will for the blocking diode tip. Rained all day Thursday and I still was getting over 200W. The shade is nice too.
Wouldn't the systems almost have to be separate considering the voltages?

View attachment 55674

Very cool!

 

[Tom Morrissette]

I'm thinking yes, I'll have to keep things as separate systems unless I don't charge at the same time; and even then I'm not sure if there's a simple way to switch from the 12v to the 36v without it becoming too much hassle. I'm leaning towards an on-board 36v charger on the boat that I plug into an inverter on the camper. I do want to try and stay reasonably simple.

 

[circus]

I've got an upconverter to power my 19v computer from a 12v cigarette lighter outlet. No messing around inverting 12v dc to 120ac to power the 19v computers brick. Doubt there's a 12v to 36v upconverter (charger), at least big ones, and I believe charge controllers only downconvert. Which brings up another question. Would a 100w panel even charge a 36v battery?