The last camping trip was a week long during a lot of cloudy weather. I noticed that the 220 watts of solar panels on the roof had a hard time keeping up when I was watching TV and the refrigerator was running. The solution -turn off the TV? No way, I added two more 90 watt solar panels! However, this time there was a twist (pun intended). The only area I had left on the roof was the poptop. It's already heavy so there was no way I could add traditional framed panels, I wouldn't be able to lift it. Enter eBay with a 90 watt, high efficiency, flexible solar panel that only weighs 4 pounds.

The panel is 19% efficient, which is quite a bit higher than my nicest panel, a KD135 Kyocera (which I think is around 14%). It's set up for charging a 12V system so a traditional PWM controller can be used. The panel voltage is compatible with the existing panels at 17.6 Vmp so I could run all the panels in parallel if it made sense to do so. I had a Sunsaver 10 left over from the last system upgrade so I'm using it to control the new panels. The two existing panels are being controlled by a Sunsaver MPPT but it's tapped out with the 220 watts already connected to it. I'm running the Sunsaver 10 in parallel with the Sunnsaver MPPT.

I attached the panels directly to the roof using 3M VHB 4941 tape. I cleaned the surfaces with isopropyl alcohol and used a roller on the tape to ensure a good bond, per the 3M instructions. I also made sure it was warmer than 60F when I attached them. I've tried to pry them off and they feel like they're attached pretty good. I hope so as it would suck if they blew off.

Since the panels are on the poptop, the routing of the wires from the panels to the battery was a challenge. I never thought I would be adding panels to the poptop when I was building so I didn't include any wiring provisions for future panels. I ended up connecting the new panels in parallel to a power pole connector at the edge of the roof. I made a removable jumper wire that connects the panels to the Sunsaver controller behind the refrigerator access panel. I'll have to connect the panels when I pop the top and remove the jumper for transit. I'm not very happy with the lump of connectors on the roof and I need to figure out something else. However, this works for testing, I'll figure out something tidier later.

The panels are very thin compared to the traditional panels on the roof, I'm hoping the won't be in the wind much at all. They're certainly a lot smaller than anything else I've bought to date. I tested one that was tilted to the sun and it was putting out 85 watts, which isn't bad for a 90 watt rated panel.

I rolled the trailer our today and the panels were putting out 6 amps. Not bad for panels laying flat and a charged battery. That puts my roof PV capacity at 400 watts. Add in another 140 watts of portable panels and I have a total of 540 watts.

These new panels seem a little delicate, the composite surface scratches pretty easily. I don't think I would leave these in the sun all the time. Since the trailer is garaged most of the time I don't think it will be a problem. I'll need to be careful cleaning them to make sure I don't scratch them up. I keep saying I'm not going to buy any more panels but advancing technology keeps bringing out new products. Maybe I'll be buying solar paint for the trailer in the coming years...
Bruce