Question about LiFePO4 cell voltages vs. SOC and how the system works. Charged my B300S batteries to 100% via the AC500 and turned everything off as I didn’t need the system for a while. Checked individual cell voltages periodically and after a couple months, all batteries were at 3.32 or 3.33 volts. According to Bluetti’s LiFePO4 voltage chart, this suggests that the batteries are now at a SOC of approximately 80 to 83%. Since the AC500 has been off while the batteries self-discharged, it thinks all the batteries’ SOC are still 100%.
When I turn the AC500 on and plug it into the grid (as though I want to charge the batteries), the AC500 shows the grid connection, but does not start charging. Although the AC500 “knows” that the B300S cell voltages (as seen on the battery information screens) are indicating 15 or 20% less than a full charge, it appears to be prioritizing its last known SOC value (which is still 100%) and does not initiate the charging function.
This is obviously how the system is designed, but I’m wondering why it wouldn’t try to take advantage of the actual cell voltages and use them to determine the SOC and begin charging when they are showing a voltage less than the full 3.40 volt value that represents 100% SOC? Both the batteries’ BMS and the AC500 “know” what the individual cell voltages are whenever the system is turned on and it seems like that might be able to give a more accurate SOC than the current methodology, although I’m probably missing something due to my incomplete understanding of how everything works.
@TMan
After verification: The current system does not use battery voltage as the initial SOC value but retains the capacity value at shutdown. You may try discharging it slightly and then recharging it to observe the result.