The solar Testbed has been running for a few weeks. I decided to leave an LED light on 24 / 7 just to see things cycle. Maybe 10W for the bulb another 10W for the inverter and logger. Everything is fine until there were a few cloudy days in a row. Eventually the battery fully drained, turning off the logger (the Raspberry Pi was plugged into the inverter).

I turned off the light for a few days and the sun came out and let the battery charge a bit. Expecting sunny days I turned on a larger load, maybe 60W, just to see how this cycled. Also plugged the Raspberry Pi into the wall so logging wouldn’t stop. It seems the controller is set for something called BatteryLife which is used to conserve battery life in lead acid batteries. This keeps the load turned off until the battery gets a full charge, to prevent short cycling. But I have a lithium battery and don’t care so much. I need to change this and try again. Anyway, the light would burn for a few hours in the evening and then turn off sometime in the night, charging again in the morning. But again a string of unexpected cloudy days moved in. Not enough panels + battery to keep a 60W load going full time. Lesson here is being completely off grid might be harder than it looks.