I'm setting up a simple portable solar system primarily for ham radio and a diesel heater. I have a single 12V 100aH LiFePO4 battery, a 30 amp MPPT charge controller, and a 200Wh solar panel. I'm considering adding an AC-DC charger with a 14.6V output for charging from the grid. My main questions are: Can I connect the charger directly to the battery? Will I need to worry about the current or voltage potentially backfeeding into the controller from the battery connection? Or should I plug the charger into the PV connection of the controller instead? I've heard mixed things about that approach. Any insights would be appreciated!
2 Answers
If you're worried about backfeeding energy into your MPPT, just know that as long as you’re not charging with both solar and AC at the same time, you should be fine. Most users prefer connecting the charger directly to the battery in setups like yours. Just remember to keep an eye on the charging process to avoid confusion with the MPPT reading.
You can go ahead and connect the AC-DC charger directly to the battery. Just make sure to include a fuse or breaker to protect the circuit. One potential issue is that the MPPT might misinterpret the battery as being full when you're using the charger, especially if the battery is nearly full. But typically, the battery voltage will regulate the system, so it should work fine together without too much hassle.