Start by separating a display problem from an energy problem
A battery showing 40% state of charge does not prove that exactly 40% of nameplate energy is available. The displayed value is estimated by the battery-management system from voltage, current, temperature, historical charge throughput and manufacturer algorithms. If the percentage begins jumping, sticking near a limit or reaching empty much earlier than expected, first record what the system actually did: starting SOC, ending SOC, delivered kWh, load level, temperature, alarms and whether grid or PV charging was active.
Check software and system context before assuming cell failure
Firmware, inverter-battery communications and reserve settings can change what the user sees. Confirm the exact battery and inverter models, current approved firmware pairing, backup reserve, minimum SOC and any time-of-use automation. Melnti’s BMS communication checklist is useful when the displayed SOC, inverter status and battery status disagree.
Calibration procedures are manufacturer-specific
Some systems periodically relearn their usable range during controlled full-charge or full-discharge events; others explicitly warn against owner-initiated deep cycling. Do not invent a “calibration” routine from another battery brand. Follow the manufacturer’s current service guidance and let a qualified installer handle any procedure that requires electrical access, firmware tools or changing protected parameters. Repeated deep cycling solely to force a percentage reset can add unnecessary battery wear.
Build a service record that can support a warranty claim
Save screenshots and export monitoring data before settings are changed. Record dates, ambient conditions, usable-energy observations and error codes. Compare the symptoms with the usable energy and degradation guide and the battery warranty documentation checklist. A consistent evidence trail helps distinguish normal estimation behaviour, a configuration issue, communication loss and genuine capacity deterioration.