Solar educationAuthor: Dave Date: 01.28.26 - 8:18pm Ok, so I got a little more than i bargined for.. I bought 10 "tested" panels off of a guy on facebook marketplace. He showed a pict of pallets of panels. I figured he was an installer or a dealer. I knew 0 about solar panels so I was trusting. $50 each for used 235W panels. First up, they all came with the leads cut 1" out of the junction box. The bullect connector inside propiritary. Not supposed to solder this, so I had to do some testing and come up with my own butt crimp that latched onto the existing wire coming out of the bullet, and still fit inside the junction box. Ok cool i figured it out. (I also found some old new stock on ebay of exact sample junction boxes with the perfect connectors so I had 6 panels covered right there) 
Next, i figured Id test the panels to see which ones i wanted. I only needed 6-8, i figured id be safe buying 10 just in case. Here were my test numbers.
oof! Now talking with teh guy turned out he lived in a tiny home with 4 other families on teh same property. Immigrant. I dont think he was a dealer or installer. I believe he was actually acting like a broker and took a pict of some other guys pallets of solar panels! His testing was probably open voltage only..obviously not under load ampage. Only 3 of these panels are decent and some are outright junk! So i figured I would screw around. I took the 60 watt panel and snipped out the diodes and retested to see if one had shorted and was sucking current. Nope. I then meansured the diodes on the bench, all fine. Ok..so my solar tester needed more than 12v to turn on, so I disconnected the strings at the junction box and differential tested the different cells of strings
Since my meter couldnt test one string on its own, i ended up ordering a dc ampage clamp meter. I also build a load bank of 3s3p halogen bulbs. I will add those results once i get the new meter in. My current one wont do DC current. So what can I do..what can i do. Well how about I hook a power supply up to each string of cells and pump a couple amps into them and see what heats up on the thermal camera?! Bingo! Check out these results... 
Image 1 shows a nice even distribution, the current is making it to all the cells and their interiors. The other two images, only the bus bars are really heating up. The cells arent getting much electricity. Seems like they arent working right. This is mirrored in the differential outputs measured above. #3 must be the worst. What surprised me is that the panel visible looks perfect. No corrosion on the bus bars, the junction box was clean. It looked like a great panel, but...total junk! Also remember Voc no load testing also means nothing. You will get Voc at panel rating even on a cloudy day. You must know the amp output and if current will collapse the instant you apply a load. Voltage no load is just a saturation state. When I can load test each string independently then it will be more clear. So I got an education...I think I am going to sell off all these panels as a lot for $100 or something and just buy new ones. I need 120v for my charger to start, which means I would have to start using my mid panels. Not worth the labor of hanging them. bleh! but i wouldnt have learned this any other way.. Here is the solar cart i put together for it. 
Ok, so I finally got the Solar array all setup. I ended up ditching the old panels and buying new. The old panels were to mismatched. Im glad i did too. 
This is 4 Trina solar 435w bifacial panels. 53Voc, 10a. 1740 face rating, but the vertical mounting degrades that. April 16th I had a peak of 700w. This will continue to dwindle until the June 21st summer solistace. I did however oeder some materials to make ground reflectors which will probably get back in business cheap. I went with vertical mounts for convenience on several fronts. First..easy to mount. Second they take up no real yard space. These are for emergency use only so it was a good trade off. I was able to charge my 100ah battery 50% in 5hrs. My fridge only uses 25% per day, so I have a 2x safety factor, plus a gas generator backup. I will be interested to see how the reflectors increase yield. You will notice two electrical boxes mounted. I have the string in series at 200v, and I added a mid string fuse so I can shut down the string into blocks of two for safer maintenance. Also each panel only uses end clamps so I can replace any panel on its own without headache. It was also easier to install solo. Speaking of solo mounting. To hang the panels alone, I screwed a temp rail to the posts. This gave me a ledge to rest the panel on. I then strapped it to the frame and was able to install the mounts effortlessly. Comments: (2)On 04.19.26 - 12:48pm Dave wrote:
On 04.29.26 - 11:17am Dave wrote:
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