Unofficial Forum Librarian
I am posting this here on behalf of an acquaintance on another forum, since the good folks here have much more expertise in this area than the people in the forum it was originally posted to. Can anyone help diagnose the problem here, or point out any obvious things to test?
Now, the battery bank is giving me some problems, so I'm hoping someone here has an idea of how to proceed. I have a 24v LiFePo4 bank with 120 amps capacity. The positive terminal is wired to a 100 amp inline fuse, which then goes to the master battery switch on the electrical panel, but it also goes directly to the positive terminal on my AIMS 2kw inverter/charger. The negative terminal of the batteries is attached to the BMS from electrical car parts company, which is then hooked up to a Victron Energy BMV-700 shunt for battery bank monitoring. That shunt, like the inline fuse, is attached to both the negative bus bar at the electrical panel, and also the negative terminal on the inverter/charger.
Everything was working great--the inverter/charger had charged the batteries to max capacity, and when I unplugged the shore power, found that the batteries could power my shop vac no problem through the inverter. Great. Well, after I topped up the batteries overnight, I unplugged the shore power and turned the inverter off. The battery voltage then rapidly dropped from 26 to 24 to 22 and then the BMV-700 display went blank.
I tested the voltage of the batteries themselves, and they were good (like 26-28v, I don't remember). Then I tested the voltage between the shunt and the fuse, and it was like 4v. I disconnected everything, and reconnected it again, and it went back to normal. Okay.
A few days later, the same thing happened. I suspected the inverter was the culprit (because it happened only after I turned it off), so I disconnected the inverter--but it didn't work. I disconnected everything again, and reconnected, and it went back to normal. But this time, I left the inverter disconnected. A few hours later, I noticed it had happened again. So obviously it's not the inverter, it's either the shunt or the BMS.
I can't trouble shoot for a while, but has anyone heard of this happening? Anyone have any ideas? Is the shunt confused and blocking the battery power? Or is this normal?