I've bought two of these so far and they both work fine. They will get hot if you don't install a fan. The lifespan of any electronics will be shortened if they get hot or hot. Use them at 3570W on one panel and 4140W on the other. 9/27/2017 This charge controller worked perfectly. I increased the battery bank to 16 golf cart batteries, two banks of 8, and the controller works very well.