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)

  • \$\begingroup\$ A diagram would be really helpful. But if you have a transformer, why are you bothering with the solar panel and battery at all? \$\endgroup\$ – Simon B Jan 13 at 14:33
  • \$\begingroup\$ By "transformer," I suspect that you mean an AC-DC voltage converter that provides a regulated DC voltage of 12 volts. If that is the case, you can probably do what I think you are describing. \$\endgroup\$ – Charles Cowie Jan 13 at 14:56
  • \$\begingroup\$ Are you concerned about how much electricity the transformer might use? Which solar charge controller are you using? Have you considered reducing the power consumption by eg. using a less hungry board than the Pi? \$\endgroup\$ – Bruce Abbott Jan 13 at 14:57
  • \$\begingroup\$ Basicly i'm concerned that the fact the power brick left always plugged in to the system, even with the diode, might represent some hazzard that im not aware by lack of knowleged. I'm mixing a new power source and letting the voltage regulate everything alone. \$\endgroup\$ – Teker Jan 13 at 16:01

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