Quote:
Originally Posted by Bill
I'm not rickst29, and I am not an expert. But - if the panels are wired in series, and one panel is covered, then my understanding is that the total output would be spoiled.
But these are high voltage panels, and you would probably wire them in parallel. If so, and if you laid the panels crosswise on the rear roof, and arranged them so that when the trailer is closed, one panel is still fully exposed, then I believe that the uncovered panel would continue to produce output as if the others were not there.
Is a single 90-watt panel enough to charge your batteries while on the road? That is a different question. Probably not, since the refrig draws something on the order of 120 watts. But maybe two 90-watt panels exposed?
Bill
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With panels having just one to four "strings" of diode-separated segments, and shade on most of on panel, there is often a big advantage in setting them up parallel - exactly as Bill describes.
But these are 24V panels- you need an MPPT in any case, and nearly every MPPT can handle at least 100W of maximum
Open Circuit voltage. (In this particular scenario, two panels @ 33.6V is about 67V; it would become a bit higher in cool, clear conditions at any significant altitude). I suspect that, overall, a pair would best be wired in Series instead - less wire loss on the "PV side" wiring, and a bit of extra power yield at the start and end of the day.
A bigger configuration (for boondocking), 4 * 90W, would probably need to be wired as 2
parallel strings of 2 panels in series, at the same 'Open Circuit' voltage.
- - -
My comments on the "different question": SInce this would be an MPPT configuration, you really could expect to get a full 90W while driving down the road near noon in early Summer. (Maybe even more, in mountains.) One panel wouldn't charge the batteries, but it would greatly assist the TV in preventing Fridge operation from digging a hole into the batteries so quickly. The TV, and it's very long wiring to the Converter's Distribution panel (and then to the Fridge), would need to provide only 30-50W to keep the batteries from becoming depleted, instead of the whole 120-140W. (Don't forget, the Norcold Fridge element is a simple resistor, which will consume MORE power when voltage is high.
The Amps
and voltage drop on the TV-to-TM-Panel wiring would both be greatly reduced, in comparison to running from TV and TM batteries alone. In the latter configuration, the batteries can often be drained quite fast, because the wire length (and possibly thin gauge) form the alternator can't "hold up" to the battery voltage, as seen at the DC distribution panel, at higher levels of current. The total current can end up coming primarily form TM batteries, rather than the TV alternator.
