Battery Management System — Cell Overvoltage
The BMS detected one or more cells exceeding the maximum allowable voltage during charging or regenerative braking. This can indicate cell imbalance, BMS calibration drift, or a failing cell.
Do not charge with active overvoltage warning.
Estimated Cost
$0 – $7,000
Repair Time
1–2 hours (service appt)
DIY Difficulty
Professional Recommended
Can I Fix This Myself?
Professional Service Recommended
This repair involves high-voltage components or specialized equipment.
What professionals will use:
Use the diagnostic wizard below to gather information for your mechanic, then find a local EV specialist using the ad below.
Check Your Warranty Before Paying
Federal law requires EV battery warranty coverage for 8 years / 100,000 miles minimum. Many manufacturers offer 10-year coverage. An authorized dealership can confirm coverage for your VIN at no charge.
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San Jose, CA
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San Jose, CA · 4.8★
Step-by-Step Diagnostic Wizard
Answer each question to narrow down the root cause of your BMS_u029 fault.
Check Vehicle Driveability
Step 1 of ~5
Attempt to enter Drive mode. Note if the car is in Limp Mode (reduced acceleration), displaying a red battery warning, or completely unable to drive.
Is the vehicle driveable (enters Drive mode) even if showing warnings?
Need hands-on help?
Find a verified EV mechanic or dealership near you.