I bought 4 of these solar panels in June 2021, for a total of 400W. After delivery I tested the open circuit voltage (Voc) and short circuit current (Isc) and both were roughly as specified so I installed them with spacers (corrugated plastic) on the roof of my Airstream travel trailer. After installation the maximum power delivered was about 200 Watts which was lower than what I expected. I was disappointed, with that outcome, but initially attributed it to the rounded roof, the higher temperature of the panels, etc. But then the output went downhill even in the very best conditions. In winter the maximum power delivered was about 100 Watts which I attributed to the sun being low on the horizon. But in June 2022, with the sun high on the horizon, the sky bright blue and at noon, the power delivered was about 40 Watts with new LiFePO4 batteries about 15% discharged. I also realized that all four solar panels were badly delaminated.I contacted the seller because it was four days before expiration of the one year warranty period. The seller asked me to take measurements at the panels, which I did. The measurements showed what I already knew: Voc around 19V and Isc between 0A and 1.6A dependent on the panel. A typical case for failing solar panels. The seller didn't like my measurements and accused me of lying.The only positive thing about the solar panels was that the seller agreed to refund the money for the faulty solar panels. But the seller insisted that I returned the solar panels on my expenses, which was about $60. Also the seller insisted that I payed 18% restocking fee, which was ridiculous. Theses solar panels were faulty. I didn't return them because I didn't like the color or something. I wanted to return them because they very obviously were not working. That meant another $90 gone for no good reason. All together I lost $150 with these solar panels.In the meantime I bought 4 x Sunpower 100W flexible Panels and 2 x Sunpower 50W flexible Panels from another vendor and installed them on the same Airstream travel trailer. They are a complete other league. These solar panels deliver about 200W in the midst of winter. I can't wait for summer to see how much they will yield.