Theory and operation
A weak cell often separates most when current flows and may recover at rest; temperature gradient and state of charge strongly affect the apparent delta.
Battery & High Voltage / Diagnostic guide
BATTERY IMBALANCE DIAGNOSIS.
Distinguish normal cell variation from repeatable weakness under load or charge.
EV GUIDE07/24
Use this guide to organize evidence. Vehicle-specific high-voltage access, measurements and component isolation require OEM procedures, appropriate qualifications, rated PPE and approved test equipment.
GUIDE PURPOSE
Diagnose the system—not one isolated value.
Confirm vehicle state, operating conditions and the full DTC record before clearing evidence or opening the high-voltage system.
Diagnostic evidence
Trend cell-group voltage, module temperature, pack current, balancing command and power limits during the same controlled event.
Safe diagnostic path
Compare repeated charge and discharge events, confirm sensor plausibility and follow OEM pack-level or module-level service policy.
Boundary and common error
Do not force deep discharge, overcharge or unsupported balancing to exaggerate a difference.
Specifications, connector access, disable sequences, wait times and allowable tests vary by model and voltage architecture.