My Multiplus-II for some reason is overvolting my batteries- Settings confirm bulk voltage is set to Lithium profile, 14.4 Absorption, etc, but for some reason it’s deciding in Absorption and bulk seemingly at random to dump 17 or more volts into them. I thought maybe it was firmware so I upgraded, and it immediately did it again anyway. I’ve had to disable the charger function as it swelled one of my batteries badly and I’m afraid it’s going to pop the other now I’ve cut the battery bank in half with just the 1 battery that’s unswelled.
You need to check if the battery can charge to 14.4V. It’s completely normal for the charge voltage to increase when the battery disables the charge MOSFET or disconnects completely. If it’s a brand new lithium battery that has not been top-balanced, they usually get to 13.8 13.9V before one cell goes over voltage.
You will have to do some testing.
So if the battery disables the charge mosfet… is the 17v from the multiplus normal? or a problem?
Topped off is in the 13s, 14.4 is just the voltage applied for absorption charge, not actually what the battery will go to.
The multiplus needs a reference voltage. If you have a load that will not tolerate the higher voltage, then you will have a problem. MPPTs do it as well. They will voltage spike when the BMS disconnects.