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100 Watt HQST Panel Comparison

We stuck with 12 v system as that’s what was already in place. But now I’m wondering if that’s really the best option, as the panels are not generating anywhere close to what we had anticipated. And with the very limited rooftop space on the truck camper, and the investment in the 520 amp hr battery capacity we now have, I’m thinking that the solar is not capable of keeping the batteries topped off let alone give us the ability to use the dc electric while the suns out. (Thankfully, we have been driving a lot, and the dc dc charger has been working awesome! We are running the fridge off of it much of the time and the batteries seem to be staying at 100%.) But the plan was to stay at a place for a month at a time and not need to use shore power if we can avoid it since we had installed solar. Right now we only have installed 2 100 watt HQST panels in parallel…but it’s no where close to even generating half of the expected watts (its not even reaching 80 watts let alone 180 watts) and we have 2 additional 100 watt panels we can add, so maybe if we do 2 series and 2 parallel that will help … plus we can’t go over 400 watts as that’s the limit of the Epever tracer 30 amp SCC we have currently…
Your statements seem true. In my head solar calculations say your system with 400 watts of panels is capable of around 120 amp hours of production. 120 ah would be OK for me for most nights, but I would not be able to use any high wattage loads for more than a couple minutes at a time. My microwave draws 155 amps, which if I used that to watt 2 meals up at two minutes each, three times a day, that would pull 30 ah alone. Idle draws can add up, like my inverter at an amp an hour, or 24 ah if I do not shut it off, and if I forget to shut the radio off that is an additional 1/3 ah, or 12 ah. Adds up on only 120 ah of production.

Honestly what I use the most of is the 9 amp propane blower motor. My biggest usage was 165 ah, and most of that was a below freezing day with the motor blowing nearly non-stop.

Whether you set the panels up 4 in series, 4 in parallel, or two in series and two in parallel, you still can’t make more than 120 ah (perhaps the in my head calculation was off, but not by a lot).

So, to increase power production need more panels. Could add a second SCC (I have three on my RV). This second could be ground mount panels, of which for me are a much better production. I used 400 watts of ground mounted panels and these would produce more than the other 950 watts of roof mounted panels, because I kept the ground panels out of the shadows like RV vents, Air Conditioning Vents, and I could also point and tilt the ground panels at the sun, owing them three times a day. The ground panels started making power earlier and lasted making power later because of the tilt and point and move.
 
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Second panel says 64 cells but it is actually 64 half cells based on Vmp.

This makes it a 32 series cell panel. 18v Vmp on 32 series cells is a stretch, more likely yielding 15.5-16v Vmp under heating of full sun and may not work well with a 12v LFP battery using a MPPT controller. It may not have enough overhead voltage above battery voltage for MPPT controller.

First panel is 33 cell panel, a little better but still marginal for MPPT controller.

When there is not enough overhead voltage from panel, an MPPT controller will just drop back to PWM mode of operation. If you plan to run an MPPT controller on a 12v battery should go for at least a 36 series cell panel, or run two panels in series.
Would running two 33 cell panels in parallel be seen as 66 cells by the MPPT controller? Just wondering if two 100 watt panels like this would be better than one 200 watt panel with 36 cells.
 
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