I have a 12v lithium battery connected to a 150/30 victron MPPT controller and a 12v inverter coming off that (also victron). My problem is that my controller sees the voltage wrong and keeps going to float. Where as my inverter sees the voltage correctly. Below is the screenshot from my home assistant integration. “100%/Charged” is 14v for this setup.
Any thoughts around what this could be? the issue is that my controller keeps going to float rather than pushing the charge it could have.
Battery, Inverter and MPPT controller are all connected to a bus bar. Connections all look good.
Turning off the solar panels (I have an isolater switch) results in the controller seeing the voltage correctly. Turning off the inverter doesn’t make any changes.
You most likely have a high resistance connection between your MPPT controller and the bus bar. This is very common in DIY builds. When you turn off solar, there is no current flow so no voltage drop. Get your multimeter out and check voltage at each connection when solar charging. Common causes are poor crimps, screw terminals not tight enough, poor bolting torque, undersized cables and quite often the cheap resettable breakers shown below.
I replaced the breaker with my old 75/15 MPPT controller as it had a load output and re-crimped a cable that didn’t look too good. Now I’m only off by 0.2v and my controller is pumping in double the amps during the day as everything is looking right.
