AC200Max + B230 Battery, uneven discharge rates

I’ve added the B230 for about a week and noticed that the discharge % is getting further away from the AC200Max as per the graph.

I never AC charge up to 100%, usually leave up to 80% total battery for solar to top off during the day, but due to autum solar, I never get that 100% as I always have 100-200w load 24/7.

I’ve drained and charged both from 0 to 100% separately with T500.


I’m hoping that the AC200Max will be smart enough to drain BOTH batteries to 0 but will stop draining B230 (lets say 1%) to turn it off before the AC200Max battery goes to 1%, at that point, its critical and both will shut down if they continue discharge which is fine. I just dont want to see B230 discharged to 0 and off while AC200Max still has say 50%.

Same issue here and I have had my AC200 and B230 for over 2 years now. I only occasionally use solar to charge. Mosty my units are emergency backup incase SHTF. I use it intermittently. That being said, My AC200 always drops first and then the B230 picks up along the way and begins to discharge, Its uneven at first but as they deplete they get closer and closer until they are both discharging at identical rates. They both reach zero charge at the same time, charging with the AC charger is similar, one first and then the other picks up until they both reach 100%. There are a lot of posts related to this exact subject, I have fully discharged and recharged without interruption a few times to calibrate the BMS and it has helped but never eliminated the issue. I think upgrading the firmware on my battery and AC 200 would help or solve my problem, but I have read to many horror stories about firmware upgrades going wrong that I will probably never upgrade my firmware out of fear of bricking my unit. I have also read that this is a BMS issue and its really not a big deal, its just the nature of the system,. You would think they would share the load equally and discharge together at the same rate but they don’t.

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Thanks for the reply, yeah I noticed that it switches between the batteries to discharge while the other sits on standby.

I guess over time they even out, I’ll just need to trust the AC200Max logic to manage the battery discharge and that it’ll do that right thing :slight_smile:

The battery voltages between battery packs may be different. When different DC voltages are connected in parallel, the battery pack with higher voltage discharges more and the SOC drops faster when discharging. When charging, the battery pack with lower voltage has more charging current and SOC rises faster. Even if there is a difference in SOC between them, they will still be fully charged to 100% or fully discharged to 0%.

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