July 18, 20251 yr Hi all,I have 2x 16s 5.1kWh 48V LiFePO4 battery packs that use Seplos v2.0 BMS to my understanding. The system was disconnected for a few months during renovations, and reinstalled 4 months ago. Both battery packs were discharged quite low while stored, so they were individually charged back up to 100% SoC before being reconnected in parallel to the inverter. Recently I started noticing that the battery packs are NOT tracking each other's SoC %, but rather just Voltage - which leads me to believe the parallel connection is not setup correctly. After both being charged up to 100% and discharged during the day, I notice a ~10% difference in SoC:Top is the master battery 0, and bottom is parallel slave 1Does anyone have knowledge of the parallel function of Seplos BMS and whether I should expect the SoC or the PackV to track one another? Is there perhaps a communication issue between my battery packs?Kind regards,Francois
July 18, 20251 yr 1 hour ago, Karnallie said:Hi all,I have 2x 16s 5.1kWh 48V LiFePO4 battery packs that use Seplos v2.0 BMS to my understanding. The system was disconnected for a few months during renovations, and reinstalled 4 months ago. Both battery packs were discharged quite low while stored, so they were individually charged back up to 100% SoC before being reconnected in parallel to the inverter.Recently I started noticing that the battery packs are NOT tracking each other's SoC %, but rather just Voltage - which leads me to believe the parallel connection is not setup correctly. After both being charged up to 100% and discharged during the day, I notice a ~10% difference in SoC:Top is the master battery 0, and bottom is parallel slave 1Does anyone have knowledge of the parallel function of Seplos BMS and whether I should expect the SoC or the PackV to track one another? Is there perhaps a communication issue between my battery packs?Kind regards,FrancoisWhy the big difference in pack voltage if I my ask?
July 18, 20251 yr Author 50 minutes ago, Stefan Cornelissen said:Why the big difference in pack voltage if I my ask?The left and right images are at different times - look on each image there are 2 LCDs: one top and one bottom which are the 2 battery packs.As you can see the Pack Voltages are within 50mV of each other
July 18, 20251 yr Since you manually charged the batteries after deep discharge, it's likely their internal SoC counters are desynchronized, especially if the BMS didn’t perform a full learning/calibration cycle. Fully charge both packs together in parallel until they stop charging (rest at ~54.0V). Let them sit idle for 1-2 hours so internal cell balancing completes. Then fully discharge both packs together until the first one shuts off or reaches 0% SoC. Then recharge to 100% — this gives the BMS a full charge/discharge cycle for recalibration.Even if the voltage matches, cell imbalances within a pack can lead to early cutoff or SoC errors. Check cell voltage differences/pack, if any cell is more than 0.05V from the others then it needs to balance. Seplos BMS does passive balancing, but it can take many hours or days to fully balance a pack if cells are way off. Each individual battery pack BMS is responsible for balancing the cells within that pack
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