FoxESS
BmsCellImbalance
Battery Cell Voltage Imbalance
Individual cell voltages within the battery pack have drifted apart beyond BMS tolerance. Passive balancing has not kept cells aligned.
Common causes
Battery never reaching 100% SoC (balancing only runs at high SoC)Aged or degraded cellsManufacturing cell variation
What to check
STEP 1
Balance charge: force battery to 100% SoC and hold for 2-3 hours. BMS balancing circuit only operates at high SoC
STEP 2
Check Fox Cloud or battery app for individual cell voltage data. A cell >50 mV from neighbours at rest indicates a degraded cell
Escalate if
Imbalance persists after balance charge — degraded cell, escalate
Need full interactive diagnosis?
Faultpath walks you through decision trees, fault codes, and commissioning — built for solar & battery engineers.
Open Faultpath
More FoxESS fault codes