[ShrimpBurrito]

Hi Kurt,

While I live in SoCal, I am a shade seeker myself. We also mostly camp in this TM in the winter, where daylight hours are less. But, I just installed the panels earlier this year, and so have been out only a few times with them. At home though, I can readily test cloud performance. Yesterday we got epic rain here, and at least when I checked in between showers, when it was still very densely cloudy, I was still getting 20-30 watts. While that's approaching only ~10% of peak performance, it's still 2-3 amps, so even if it were like that all day, and only 8 hours of sunlight, that's still 16-24 Ah. I have no idea what your power consumption is, but that is not an insignificant amount of power, and that might be at or near worst-case performance. My peak performance is 330 watts.

That's another reason for more panels. Not because you need 300 watts, but because you need 30 watts (with a 300 watt array) instead of 20 (with a 200 watt array) when it's raining (or shaded).

Also worth considering is whether you wire the panels in series or parallel. If you wire them in parallel, the array voltage will not exceed the open circuit voltage of any one panel (probably around 20 volts). You need ~14 volts to charge a battery, so if it's cloudy you have very little buffer before the array voltage falls below the minimum voltage to charge. You'll also need thicker wire because the current to the solar controller will be higher.

If you wire in series, however, the array voltage is the sum of open circuit voltages of each panel (so, 3 panels @ 20 volts each = 60 volts). In this scenario, you can still be charging the battery when it's very cloudy, or the sun is coming in at a sharp angle (sunrise and sunset), because the voltage would have to fall far more to get below 14-volt charging voltage. Another advantage is that the wire from the panels from the array to the controller can be thinner, which is especially handy in making that bend from the roof down to the wall. The disadvantage with wiring in series is that if one of the panels is blocked entirely, the output of the entire array can be significantly degraded. There are "bypass diodes" built into each panel that bypass sections of the panel in case this happens to mitigate this effect, such that the panel can still produce output. For that reason, as I understand it, the more bypass diodes the better.

One approach you might consider is putting panels on the roof and trying it out. You know that alleviates the setup/tear down hassle, and it might be all you need. You could even do a test run, and simply lay the panels on the roof during a camping trip to do a sample test. But, if you find you need more, which may only be on certain trips, you can always add-on a portable or TV setup later. But with such remote setups, really think about how far you'd have to put the panels away from your TV so that the panels are in sun and the TM isn't. It doesn't take much to get to 30, 40, 50 feet, and your cable size is going to have to rapidly increase with such long runs.

We're going out this weekend and expect to be in shade (and freezing temps). I can report more details when we get back.

Also, note that HQST panels are made by Renogy. I think they're identical, actually, and quite a bit cheaper.

Dave