I have a 24v battery bank that has a 120v battery charger connected to it that runs when I run a generator. There's also solar panels connected to the output of the charger to help the batteries stay charged. The problem I am having (I think) is the 120v charger is seeing the voltage from the solar panel and not actually charging the batteries when it should be. I measure 27v out of the solar charger when it is charging the batteries and I have noticed the charger will not actually switch on when that happens. When I disconnect the solar panel the charger switches on and takes over charging

Is there some way I can hook this up or some device I can connect the charger output and solar panel to that will automatically manage the charging of the batteries?

From other people asking similar questions it looks like a microcontroller monitoring the voltages of the devices and automatically switching MOSFETs to select the charging source would work but is there any prebuilt product on the market for this application or am I on my own in designing and implementing this?

  • \$\begingroup\$ Depends entirely on how it’s made and your circuit. Please draw a block diagram of it. What voltage do you measure across your battery when solar is charging? \$\endgroup\$
    – winny
    Commented Jun 13, 2023 at 16:52
  • \$\begingroup\$ Purchase advice is off-topic, design on-topic here. \$\endgroup\$
    – greybeard
    Commented Jun 13, 2023 at 16:58
  • \$\begingroup\$ Ah I didn't realize I couldn't ask purchase questions. Looks like I'm on my own. Thanks \$\endgroup\$
    – joshua0823
    Commented Jun 13, 2023 at 17:14

1 Answer 1


After thinking about it for a while I think I'll just add a relay that turns on when 120v is applied to the charger which connects the charger to the battery bank but when the charger isn't on it connects the solar panel to the battery bank

  • 1
    \$\begingroup\$ This is a very good solution for most users. Make sure your relay has adequate DC voltage rating. \$\endgroup\$
    – winny
    Commented Jun 13, 2023 at 18:52

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