Those who have AC300 with multiple B300: does your batteries' percentage stay in sync?

Me and my relatives both have AC300 + 2xB300. I have noticed that in my system the difference between individual battery charges is about 10% (i.e. battery 1 can show charge of 40% while battery 2 can show charge of 50%). However, my relatives’ system seems to keep batteries in sync and their battery percentage stays within 1-2% of each other.

We both did a full discharge test with a watt meter at about 1500 watts load and one of my batteries benchmarked about 70 watt-hours less than the other (the other battery benchmarked the same as both batteries in my relatives’ system).

I’m wondering if the 10% difference between the batteries in my system could indicate a fault or if this is common.

One other difference I have noticed is when looking at the batteries info in Settings: my system shows that batteries 1 & 2 are connected, but in my relatives’ system the batteries 2 & 3 are connected (this seems to be consistent with many youtube videos; never seen any other video where 2 B300 batteries show up as occupying logical battery slots 1 & 2 as in my system).

P.S.: to see individual battery percentages, one must tap the main percentage circle in the middle of the main screen in the UI.

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I just did my first discharge to 10% from a full charge and noticed that one of the B3000s discharged about 12% faster than the other. I probably wouldn’t have thought too much about it had I not seen your post.

Not as much as I’d like. There seems to be some amount of coordination, but I hope a firmware update can make it better.

To use an extreme example: If someone has (say) an AC300 and two B300s (which is actually my setup), they may want to keep a 50% SoC for long term storage or inactivity. And that’s great if both of the B300s are at 50%, and even if they are 40/60 it’s not bad. But 80/20? 90/10? Heaven forbid, 100/0? (I don’t think the extreme examples are likely to occur, but if there is no software to try to keep multiple units in relatively close balance, who knows?)

Realistically, I think they should be able to stay within +/- 5% of each other, or even 10%.

Hi guys, I have been experimenting around this idea in the past week. I am still unable to make a conclusive decision whether the charge controller even tries to keep both batteries withing some margin of difference or not. Here is what I have noticed so far:

  1. One of the batteries in my relatives’ system all of a sudden jumped up by 20% in the past week during normal usage and charging from PV throughout the day. Since then, the difference between their batteries stayed about 12%.

  2. I swapped my batteries in my system around and now they are staying within 1-4% of each other. I have my system connected as following: AC300 “batt 1” (top) connected to battery’s “batt 1” (top) port; both batteries connected between themselves via “batt 2” (bottom) ports. Again, I’m not sure if it’s a coincidence that now my batteries are staying more in sync. I am also not using my system in the same way as my relatives. They often have input from solar in the mornings that charges only one battery (~60 to 80 watts), while I usually connect to solar when input is more than 100 watts, such that both batteries are charging.

  3. I have noticed that when input wattage is low (~60 to 80 watts, such that only one of the batteries is charging) the system switches sometimes which battery is charging exactly. I.e. sometimes only battery 1 is charging and sometimes only battery 2 is charging. So somehow the system can switch which battery is charging exactly when input wattage is low.

  4. Even though I have swapped my batteries around, I see that the “logical” assignment for the batteries is the same. The battery that was initially “#1” when connected is still the battery “#1”, even though it is now connected as the “last” battery in the chain. Therefore, I’m thinking battery logical number assignment must be based on its serial number, so it’s remaining the same, no matter how one connects them (have tries all permutations of connecting the batteries with AC300 in both “batt 1” and “batt 2” ports).

I know this might a nit-picking, but still, I’m hoping that the charge controller is at least trying to somewhat keep the batteries in sync to not let the “10% / 90%” or “0% / 100%” case happen like @ziggy29 mentioned. I’ll continue to test and observe meanwhile…

Finally, here’s how my batteries are connected (after physically swapping them around):

Did this battery chaining work to keep them in sync?

Monitoring the charging behavior of AC300 + B300 I can confirm that the percentages shown have no real value. They seems to jump with larger steps sometimes.

I is much better to check the actual cell voltages. I have 2 full systems each with 4x B300 and these volgatages are nicely synced all the time. The percentage for me is just a rough indicator not to be taken very seriously.

i can’t imagine what the Controller does. I have one Battery with 65 % (Standby) and one Battery with 36 % (entladen/discharge). I’m worried :frowning:

Have you checked cell voltages?

How can the cell voltages be checked?

This is undocumented in the bluetti documentation.

On the screen goto DATA in the main menu. Now select battery information
In the most upper left corner of the screen you see a battery symbol. Tap this symbol 4-5 times and by magic the cell voltages pop up :wink: