I got this AC200L + B300K combo to act as a UPS for our refrigerator.
I set customized UPS mode with 70% SOC for upper threshold for AC charging.
It seems to be known in several posts here that the internal components draw from the battery and slowly drain the battery which then recharges.
However, with two packs, and the SOC target of 70% this is slowly causing the packs to drift apart.
initially they were 66% (AC200L) and 74%. (B300K)
now they are 61% (AC200L) and 79% (B300k)
it appears that the AC200L is doing the self discharge, or self discharging faster, then they are both being charged in parallel til they average the 70% target again. causing the B300K to keep rising higher.
I expect they will drift until they reach 40% + 100%
Hi @Merle, Could you please provide the SN code and the current firmware version of your AC200L?
We will check if there is any new firmware available to optimize the SOC balancing performance.
Per DMs I updated the firmware on the ac200L to v1043.13
Then performed drain to 0, charge to 100% for SOC calibration as per instructions.
with Customs UPS Mode now set to 20/80% and load attached.
the AC200L drains faster then the B300K.
and once it got to around 80% the AC200L continues to drop and the B300K continues to rise.
Hi @fessyfoo, Could you also let us know your DSP and ARM firmware versions? Our new firmware is highly beneficial for optimizing the performance of the B300K.
By the way, please note that if you need my assistance, please @BLUETTI_CARE, otherwise, I might not see your message and be able to help you promptly.
That is the reason why we can’t reply to you in time.
@fessyfoo , just mentioning to help: FYI you need to tag @BLUETTI_CARE per their response to you in their last message: "By the way, please note that if you need my assistance, please @BLUETTI_CARE, otherwise, I might not see your message and be able to help you promptly. That is the reason why we can’t reply to you in time"
Hi @fessyfoo, I have forwarded your information to the engineer, who confirmed that all your firmware is already updated to the latest version. Therefore, no further firmware updates can be pushed.
We can only suggest recalibrating the battery. Please note that a certain level of SOC discrepancy is objectively inevitable and acceptable. The entire system will maintain dynamic balance, ensuring no impact on actual usage.
@BLUETTI_CARE , when you say “The entire system will maintain dynamic balance, ensuring no impact on actual usage”, are you meaning that there is no system capacity lost? If so, could you clarify how that would occur?
I thought that with this large of a capacity difference (AC200L is ~50% SOC while B300K is at ~100% SOC), wouldn’t the system shut down earlier due to the 200L running out of power?
@BLUETTI_CARE note, recalibrating capacity was done, and the issue persists.
or with the current custom ups 20% / 80% settings. i’d expect 60% and 100%
however it does seem to have hit steady state at
65% AC200L and 95% B300K
I suspect this means that the B300K will age worse than the AC200L because it’s battery will spend more time at a higher SoC. which is the reason I was concerned in the first place.
Hi @jCs, We completely understand your concern about this issue.
We previously addressed this issue in another post regarding the SOC discrepancy between the AC200MAX and B230. Here, we would like to reiterate our earlier response.
From our perspective, the power station and the battery pack are designed to function as a unified system. Therefore, we focus more on the overall performance of the system rather than on individual SOC discrepancies.
If the entire system can charge to 100% and discharge to 0%, we consider it to be functioning normally.
The SOC difference arises due to the inherent characteristics of the product. Our batteries use premium lithium iron phosphate (LiFePO4), which is exist the inconsistency among cells. This inconsistency stems from the high internal resistance of LiFePO4 batteries. Each cell’s internal resistance varies slightly, causing some energy to be consumed by internal resistance during charging and discharging. Over time, this leads to increasing discrepancies in the charge levels of individual cells.
Additionally, during the redox reactions, ferrous iron (Fe²⁺) may oxidize to ferric iron (Fe³⁺) or reduce to metallic iron, potentially altering the internal resistance of the battery.
Coupled with SOC measurement error, overcharging or over-discharging individual cells can further affect internal resistance. This may eventually result in varying SOC levels among the cells in a battery, which is a common manifestation of LiFePO4 cell inconsistency.
Hi @fessyfoo, We would like to confirm if your recalibration process follows the recommended steps. If the SOC difference between the units is significant, you can try disconnecting them, then charging or discharging the AC200L individually. Once both units have matching SOC levels, reconnect them. This helps manually minimize the SOC discrepancy.
The AC200L and B300K operate as a single system, so a moderate difference in SOC is acceptable. While they strive to maintain balance, achieving absolute parity is not feasible.
@BLUETTI_CARE understood on this and that makes sense But also curious to understand, what is considered normal disparity? You mentioned “absolute parity is not feasible”, but the SOC differences people are talking about are eg a large 30%, and (of course) those people can’t be said to be trying to reach perfectly matching charge
So hence trying to understand, is 30% considered large by Bluetti, or is that considered normal? (This is genuine question and not a leading question )
Hi @jCs, Thank you for your attention to this matter.
We do not set a specific normal or abnormal value; everything is based on the customer’s feelings.
If a customer feels the difference is too large, we will try to maintain a relative balance using the new firmware. Additionally, the customer can recalibrate, especially when ensuring that each battery’s charge level is consistent before connecting them. This can be very helpful.
@BLUETTI_CARE in this case. there’s a load. a refrigerator attached. and the AC200L+B300K are plugged into the mains. the ac200L is in custom UPS mode. in custom UPS mode the unit is not acting like a UPS, powering from mains unless mains is lost, instead the load is being powered by the battery and then the battery is being recharged from the mains. as this happens the SoC of the AC200L goes down, and the SoC of the B300K goes up as far as it can.
Hi @fessyfoo, Could you provide a screenshot of how you set it up? We would like to confirm your settings, such as which UPS option you selected, the SOC value, and the time period.
Under normal circumstances, if charging is not allowed, bypass cannot occur, and the AC200L’s power will be consumed instead.
But also curious to understand, what is considered normal disparity? You mentioned “absolute parity is not feasible”, but the SOC differences people are talking about are eg a large 30%, and (of course) those people can’t be said to be trying to reach perfectly matching charge 
)