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diy solar

Mixed solar panel considerations for 24v all-in-one system in a small camper

kaid

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Jan 8, 2022
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Hi folks, my family and I are taking delivery on a new 16' Scamp in May (yay!) and I'm planning to swap the group 24 lead acid battery for a LiFePO4 setup and 2000 watt inverter. Other than an induction cooktop, our power needs are currently pretty light - a DC fridge may be in our future at some point but not going to swap that out any time soon. Thinking about a Growatt or MPP plus 24v battery. The inverter won't be running much, maybe 20 min a day so not worried about excessive drain.

I may have 150-250 watts of solar on the roof, I'm still unsure exactly what my working dimensions are and I'm also loathe to punch holes in the roof of my brand new camper. And then either a single 100-150 watts in a fold out panel in addition to the roof panel OR just using two fold out panels when we camp and ditching the roof panel altogether. I'm wondering about how to meet minimum voltage requirements (30v) of an all-in-one given these solar sources. Folks more often concerned about the max voltage limit and here I am concerned with minimum!

Options as I see them - any better ones?
  • Roof panel(s) @ 30v minimum is easy, we try to park in the shade so more power generated when driving than at camp
  • Two fold out panels in series is also easy to get to 30v (but have to always use both panels and it's annoying to have panels & wires spread across camp chasing the sun), not generating when driving - just at camp
  • Mixing a roof panel with a single fold out panel is complicated. Fold out panels tend to be about 18v - I could match that with an ~18v roof panel of similar wattage for series connection but then the roof panel doesn't meet minimum voltage when we're driving, so what's the point.
  • Fold out panel(s) with independent charge controller - lose some of the cost savings from an all-in-one if I need to add another charge controller
  • Anything better?
More context:
I've been planning to DIY 12v EVE battery with an inverter and MPPT for solar (use existing Progressive Dynamics charger though it doesn't have a specific profile for Lithium and no alternator charging) but I started looking more at the all-in-one systems and am now really considering a 24v Growatt 3000TL or MPP LV2424 with a 24v 200ah server rack battery and 24v -> 12v converter instead.
  • Pro: Automatic cutover between charger and inverter - no need to manually switch between the two with those associated risks
  • Pro: $/watt competitive with DIY using server rack battery
  • Pro: simpler and can remove the Progressive Dynamics charger - and when building/installing I often wish I had valued simplicity more during planning phase!
  • Con: higher total cost, with larger battery than I need
  • Con: if one component in the all-in-one breaks, need to replace the whole thing

Curious for any thoughts / feedback. I feel like I'm spinning with options/decisions!
 
I would go with the AIO and server rack battery.
Shore power connected to the input.
For pass through and charging.
When choosing panels, you have to reach the minimum voltage for MPPT.
 
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