Is it normal for two of these batteries to become ‘lopsided’ while charging/discharging? I charged them both up to 100% but within a week of daily use I saw one at 29% while the other was at 50%.
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What happens if one goes down to 0% while the other is say, 30%? Is there some kind of built in protection to keep one battery from being totally discharged (while the other battery still has power)?
This is not an uncommon issue on the B300 batteries. This thread talks about the issue a good deal AC300 - Different BMS on B300 and different discharging rates - #11 by BLUETTI
I have an AC300 with 2 B300 batteries. I have drained them all the way to zero to calibrate the SOC and when the lower of the two gets closer to 0% the AC300 draws more power (seemingly) from the battery with the higher SOC. So far other than being annoying, it hasn’t been a problem. My only two cents is to keep an eye on it. Don’t leave it unattended for extended periods of time when there is a constant load on it. Some users on the forum have reported their B300 battery getting discharged to extremely that they couldn’t revive it and had to return it to Bluetti for a replacement.
@St8kout Are both B300S connected to the AC500, or one by one in series? Please connect both batteries to the AC500.
Is your Bms version up to date? You can fill the batteries separately and connect them together again to see.
Yeah, each are plugged into the AC500. No updates are pending.
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The trick seems to be they have to be recharged to 100% to “reset” the imbalance back to equal charge/discharge percentage.
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When I first noticed this we had 4 days of clouds and rain, so the batteries only got recharged to about 90% when the sun peeked through. So without getting to 100% charge the imbalance kept growing day by day. It has to get to 100% to reset them to be equal.
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Maybe all it needs is a line of firmware code to monitor the imbalance (and make corrections if needed.)
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