Battery Charge and Discharge Rate Temporarily Reduced

Common Symptoms

• Touchscreen shows a yellow warning banner mentioning reduced charge or power
• Max charge rate drops noticeably at a Supercharger, sometimes capping below 50 kW even on a fast stall
• Regenerative braking feels weaker than normal, especially in cold weather
• Car takes longer than expected to charge to your set limit on Level 2 AC charging
• Range estimate on the touchscreen may show lower than expected numbers after a full charge
• Power output feels soft during hard acceleration, as if the car is in a derate mode
• Code appears in Scan My Tesla or TM-Spy alongside the yellow battery icon on the main screen

Probable Causes (Ranked by Likelihood)

• Ambient or pack temperature too low, BMS restricting charge rate to prevent lithium plating on cold cells Very Likely
• Individual cell group imbalance detected, one or more cell groups reading significantly lower voltage than the rest of the pack Very Likely
• Pack recovered from a deep discharge event, BMS applying a conditioning charge rate limit until cells are re-balanced Likely
• Degraded cell capacity in one module causing the BMS to reduce the overall C-rate to stay within safe limits Likely
• Coolant flow issue reducing thermal management effectiveness, causing BMS to derate as a thermal safety measure Possible
• BMS firmware bug or corrupted calibration data causing false derate condition that clears after a reboot or charge cycle Possible
• Failing battery coolant temperature sensor feeding the BMS incorrect temperature readings Less Likely

Step-by-Step Diagnostic Procedure

1. Check ambient temperature first. If the outside temp is below 40 degrees F, this code is almost certainly a cold-weather protection response. Precondition the battery using the Schedule or Climate app before charging and the limit will likely lift on its own.

2. Open Scan My Tesla or TM-Spy with an OBDLink MX+ or Veepeak adapter plugged into the OBD port under the left dashboard edge. Navigate to the BMS live data screen and look at individual cell voltages. A healthy pack has all cell groups within about 20 mV of each other at rest. Any group more than 50 mV below the others is a red flag.

3. Check the pack state of charge history. If the car was recently discharged below 5 percent, the BMS enters a recovery mode. Plug into a Level 2 AC charger and let it complete a full slow charge cycle to 90 percent. Check whether the code clears on the next drive.

4. In the touchscreen service menu (long-press the brake pedal and touchscreen simultaneously on Model 3 and Model Y, or navigate to Controls > Service on older models), check for any concurrent BMS codes, especially BMS_a035 or BMS_a046 which indicate cell imbalance or thermal faults that would explain this derate.

5. Inspect the front trunk frunk area and the charge port door for any standing water or moisture intrusion if the car has been in heavy rain or flooding. Water contamination near high-voltage connections can trigger false BMS readings.

6. Check coolant level in the battery thermal management reservoir, usually located in the frunk. Low coolant reduces the BMS ability to regulate cell temperature, and the system will derate to compensate. Top off with the correct Tesla-approved coolant if low.

7. If the code persists through two full Level 2 charge cycles and ambient temps are normal, the most likely cause is a degraded cell group. At this point you need Tesla Toolbox 3 or a Tesla service center to pull detailed pack-level diagnostics. An independent EV shop with Toolbox 3 access can do this without the dealership markup.

8. Do not attempt to open the high-voltage battery pack yourself. The pack operates at over 400 V DC and retains lethal charge even when the car is powered off. Any internal battery work is advanced territory requiring trained technicians.

Frequently Asked Questions