How to solve Error Code 31

Fault code:

【31】Low capacity battery shutdown (effective after successful BMS communication)

Reason:

The main reason is that the BMS system misjudges the battery capacity, resulting in premature protection or abnormal communication protocol between the inverter and BMS.

BMS system misjudgment leads to premature protection

1. SOC estimation deviation: Due to inaccurate algorithms, some low-end BMS may result in a power estimation deviation exceeding 10%, triggering protection mechanisms. For example, when the actual remaining power of the battery is 20%, the BMS misjudges it as 5% and cuts off the power supply in advance.  ‌

2. Balance management failure: The voltage inconsistency of individual cells in the battery pack exceeds the threshold (such as exceeding 50mV), and the BMS fails to balance in a timely manner, resulting in the overall capacity depletion of the pack.  ‌

Communication protocol abnormality

1. Baud rate mismatch: The communication baud rate between the inverter and BMS is inconsistent (such as BMS actually using 250Kbps while the inverter is configured as 500Kbps), resulting in data transmission failure.  ‌

2. DBC file configuration error: Communication protocol parameters (such as variable offset and data format) were not configured correctly, resulting in instruction execution errors.  ‌  ‌‌

Solution:

1. Optimize BMS parameters

Adjust the accuracy of SOC algorithm to reduce the probability of misjudgment

Regularly calibrate battery cell voltage balancing strategy

Ensure that temperature management parameters are adapted to actual operating conditions (15-35 ℃)

2. Check communication configuration

Check if the baud rate and data format of the inverter and BMS are consistent

Reconfigure DBC files to ensure accurate data transmission

3. Strengthen environmental management

Avoid working the battery in high temperature (>35 ℃) or low temperature (<15 ℃) environments

Ensure good ventilation and reduce electromagnetic interference.

Note: Please do not dismantle the machine without permission, otherwise it will be out of the warranty of Ktech.