I have a Victron MPPT 100/50 charge controller (firmware v1.61) charging a 1180ah 12v LiFePo4 battery bank. I have two 370w panels, flat mounted, on the roof, wired in parallel. When both panels are connected at high noon, sunny skies, I get about 315w to the battery. Each panel is showing about 35v and ~4.5amps, with the charger outputting ~13.5v @ ~23a. Seemed a bit low.
Note that my battery system is currently at only 30% SOC since I've had the solar disconnected for a couple weeks. So there's plenty of room left to accept amps. When I hook to shore power, I have no problem feeding in 100a to these batteries.
To test, I decided to isolate each individual panel. I hooked panel one up directly to the charge controller and saw the same output voltage from the charger. 315w. Obviously the amperage from the panel was greater, at 9a.
Second panel had the same when hooked up to the charge controller by itself. 315w max output at the batteries.
To further test, I tried wiring the two panels in series to the 100/50 MPPT. Voltages doubled, amperage halved, still 315w output with the two panels.
Something is limiting the charge current, and I do not understand what it is. I would expect to be getting 630w to the batteries from this setup given that each panel individually is charging at 315w.
I am not running DVCC on the system. The charge limit on the MPPT controller is set to maximum 50a, but I'm not able to get anywhere close to that. Absorption voltage is 14.2v, float is 13.6v.
As an aside, but potentially related, I noticed that the MPPT really wanted to go to float early. I have no idea why the MPPT controller would even leave bulk at such a low SOC, much less go to float. Also, my float voltage is 13.6 in the MPPT settings, and while in float, the battery voltage was only 13.35. Re-bulk voltage offset is .1v, so I would've expected the controller to go back to bulk with the voltage down at 13.35
Any ideas would be much appreciated.
Thanks,
Sam
