I have a small solar setup running with a low capacity battery plus a 100w solar pannel and i have 3 raspberry pi's getting juice from it. The thing is that sometimes with a cloudy day i can have my batteries runing low on voltage. Can i have a transformer hooked up to my load with a diode to prevent the eletricity to go to the transformer when the voltage is higher, and let the power flow from the transformer to the load as the battery voltage goes below? Or should i put relays to switch the power source? (batteries / transformer)
What can go wrong if i take the simpler aprouch? can the transformer be back feeded when the sun is shining even with the diode properly placed?
The system is 12v rated the transformer too, near the load i have at minimum 10.5v and when the sun is shining its near 14v.
-The transformer its just a 12v power supply from a old WiFi router;
-I'm doing this just to learn / have fun, i know that i can toss the pannel and the battery away and plug everything to the wall;
-I can reduce power, but i cannot power off all the RPI's its a web server (or a cluster :P)