Battery discharges unevenly

Hello everyone,

I have an AC500 with 4x B300S. I’ve only been using the power station for a few weeks. Now I noticed that the state of charge of the batteries are extremely different.
total charge=50%
battery 1=65%
battery 2=70%
Battery 3=27%
battery 4=38%
I have the SOC at 30% and am now “afraid” that e.g. battery 3 will be deeply discharged because it is already extremely different.
what can you do about it?

The batteries are each connected in series on the two terminals of the AC500

BMS version 1022.08
DSP version 4047.03
ARM version 4048.02
HMI version 6052.04

Can someone help me here?

Having four expansion cables and two expansion battery ports, I suggest swapping cables and batteries between the two ports in order to localize the weaker charging port or the bad expansion cable. Many others and myself have done this procedure and have localize the bad component or resolved the problem, since the AC series of controllers and their B series batteries are sensitive to the expansion cable connections. I hope Bluetti eliminated this problem with the new AC900 model.

1 Like

@J0hnny Based on this question, @BLUETTI_CARE team will offer you detailed and more professional advice.

I just added a 4th B300s and twice now, after topping all the batteries off at 100%, this new battery stays in “Standby” mode while the other 3 discharge. Today, the other 3 were in the 70% range while the new battery stayed at 100% on Standby.
Yesterday I powered everything down and when it came back up the new battery started discharging normally. So I did the same thing just now but I also swapped some cables around while it was off. I turned ONLY the new battery back on and it started discharging like it should. If it happens again a 3rd time tomorrow I’m going to need some help.
It sounds like the software has a problem with 4 batteries. When I had 3 they all charged/discharged at almost the same rate.

1 Like

When I swapped cables around, the Head unit would not turn on (all the battery green buttons were lit.) So I swapped cables around again and then the Head unit came on. I “daisy chained” them but I was using only one of the Head unit ports; it didn’t like that.
I now have 2 batteries on each of the Head unit ports.

1 Like

@J0hnny Please update the firmware version to 1022.09, and then do several times of cycles one by one to test.

I would like to ask a Bluetti engineer whst is the limit of B series batteries attached to each expansion port of the AC300 and AC500 controllers. Maybe all of the batteries can be serial connected to just one port since they are actually in parallel, and the firmware will recognize and assign a battery pack number to each.

I did that and the AC500 would not turn on. Pressing the on/off button did however turn on all the batteries, so electrically they were all connected and communicating with the AC500.