24v system with 12v starter


Solar Enthusiast
Looking to build my first DIY LFP battery to replace my pair of 12v FLA group 24s (guesstimated 85ah each) in my slide-in truck camper.

Originally I was set on just building a 12v 4S 280ah to replace the pair of FLAs mentioned above. Most of the big 'load' wiring would be pretty well concentrated in one area, maybe within six feet of each other (most of it much less). I came across some discussions that sparked my interest in the possibility of going with a 24v system, mainly for the sake of some of the optional upgrades I'd *like* to have - 3000 watt inverter charger, vs. 2000, maxing out the solar on the roof, etc.

One complication is that I have an onboard Onan 2500 LP generator, which is started via #4 cables ran directly from the battery terminals. I put a clamp-on ammeter on the positive lead last night, and cranked it up - 350 amps, at least for a second or so.

That seems a little steep for any kind of reasonable expectation from a DC-DC 24/12v converter, and I'm not sure I have the room to keep a separate, dedicated 12v starter battery - though I don't know how small of a battery I would really need if that's *all* it's going to be used for.

Any thoughts or suggestions? Better to stick with a 12v main system, given the short distances involved and the requirement for 12v starting power for the generator, or are there other options besides a dedicated 12v house/starting system that I should be aware of?


Solar Honey Badger


Solar Enthusiast
Separate question.

Exploring options at this point, so I imagine it may appear to be all over the board at times ;)