I have used this controller before, and I can tell you from personal experience that it's crap. It has no sense of 3 stage charging, more or less PWM. The design is really not that great, and it's not reliable. I had one managing a small bunch of 20w panels and this thing just clicked on, then off, then on, then off, constantly. Who knows how long the relay will last. Plus, since batteries have a surface charge phenomanon (when the battery voltage is high, yet the actual charge level of the battery is lower. So the voltage usually would rise under charge, trip the controller, and then dump power when the battery's not fully charge. Then it began malfunctioning and saying my battery was fully charged at guess what? 12.0 volts. Really? I asked the company, Coleman air, which isn't affiliated with Coleman, the common camping company, and they wanted $30 to take a look at it. I would just get rid of it.