Charging problems

Most charging problems stem from simple contact/power supply issues—poor plug contact or external power/fuse problems are the most common.

Troubleshooting steps (from easiest to hardest) – each step is explained as “Symptom → Possible cause → Solution → Precautions”:

1) Check the power and charger indicator lights.

• Symptom: The indicator light does not light up or does not respond after the charger is plugged in, and the car does not charge.
• Possible causes: The wall socket is not powered, the switch/leakage protection trips, the extension cord is faulty, or the plug has poor contact.
• Solutions: Try a different outlet or connect the charger directly to a known working outlet; check and reset the circuit breaker/GFCI; do not use a damaged extension cord.
• Precautions: Ensure the power is off and the area is dry before plugging or unplugging the plug, and avoid operating in a humid environment.

2) Check the external/vehicle fuses.

• Symptom: The socket has power, the charger light may be on, but it cannot charge the battery or the power cuts off momentarily.
• Possible cause: The external fuse or the vehicle fuse has blown.
• Solution: After disconnecting the power, check and replace the fuse with one of the same specifications; if you are unsure of the specifications, consult the vehicle/charger manual.
• Precautions: Disconnect all power before replacing the fuse; do not use a fuse of too high specification to avoid damage to equipment or safety risks.

3) Check the connection between the charger output cable and the plug (poor plug contact).

• Phenomenon: Charging stops after a short time, sparks appear when in contact, and the contact area becomes hot or shows signs of carbonization.
• Possible causes: poor plug contact, contact oxidation, or cable wear.
• Solution: After disconnecting the power, clean the connector (with alcohol or contact cleaner), tighten or replace the damaged plug/cable; ensure the plug is fully inserted and securely fastened.
• Precautions: Disconnect the power supply when cleaning; avoid using a wire brush to damage the coating; replace directly if there is obvious burning or deformation.

4) Measure the battery pack voltage and the individual cell voltage (to check for voltage mismatch).

• Symptoms: The charger displays an error, is not fully charged, or has a very low charging current.
• Possible causes: The total voltage of the battery pack does not match the output of the charger, or there is a large difference in the voltage of individual cells.
• Solution: Use a multimeter to measure the voltage of the entire pack and the voltage of each individual battery; confirm that the charger’s rated voltage matches the battery’s nominal voltage (e.g., 36V/48V); recharge or replace batteries with significant differences.
• Precautions: Avoid short circuits during measurement and wear gloves; voltage mismatch may damage the BMS or battery. Consult a professional if you are unsure about any situation.

5) Locate BMS protection and low temperature protection (BMS protection / low temperature protection)

• Symptoms: The charger is connected but does not output, indicates a fault, or flashes a specific code; it does not charge in cold environments.
• Possible causes: The battery management system (BMS) cuts off charging (e.g., due to over-discharge/overcharge/cell malfunction); or low-temperature protection is activated, and the BMS disables charging to protect the lithium battery.
• Solutions: Refer to the vehicle/battery manual to view the fault codes and reset the BMS according to the steps; if the temperature is low, move the battery/vehicle to a warm environment to allow it to warm up before charging; if a single cell is abnormal, it needs to be maintained or replaced.
• Precautions: Do not attempt to force charge at extremely low temperatures or directly heat the battery surface with an external heater; repeated BMS triggering usually indicates a problem with the battery and should be further tested.

6) Check the communication and wiring (including grounding) between the charger and the battery.

• Symptoms: The charger displays a fault code, the charging curve is abnormal, or it stops quickly after starting.
• Possible causes: The communication line (CAN, signal line) is broken or incorrectly connected, or the grounding is poor, causing the control circuit to malfunction.
• Solution: Check and confirm that all control/signal cable connectors are secure and free from corrosion; consult the service manual to verify the wiring sequence; if possible, use a diagnostic tool to read BMS/charger error codes.
• Precautions: High-voltage systems pose risks. It is recommended that qualified maintenance personnel perform the diagnosis of complex communication faults.

7) Charger malfunction or temperature protection triggered

• Symptoms: The charger stops working after a period of time, or the casing becomes abnormally hot to the touch; the fan does not turn or makes abnormal noise.
• Possible causes: aging of internal components in the charger, poor heat dissipation triggering temperature protection, fan failure, or damage to the power module.
• Solutions: After powering off, check if the vents are blocked; restart and observe after cooling; use a multimeter to measure if the output voltage is stable; if an internal fault is suspected, contact the manufacturer/professional repair or replace the charger.
• Precautions: Do not open the charger casing for repair, as there are high-voltage capacitors inside that may store energy; if repair is required, please leave it to a professional.

8) Severe degradation or internal short circuit in a single battery cell (deep fault)

• Symptoms: Even when the charger is working properly, the battery cannot be fully charged, its capacity drops drastically, or the charging current is very low; the BMS repeatedly alarms.
• Possible causes: severe degradation of individual battery cells, increased internal resistance, or internal short circuits leading to imbalance of the entire battery pack.
• Solution: Check the voltage and internal resistance of each individual cell, replace the weaker cells or reset the entire battery pack and perform equalization charging; if necessary, replace the entire battery pack.
• Precautions: Battery maintenance and replacement are risky (acidic or lithium batteries are dangerous). When replacing batteries, check the specifications and dispose of used batteries properly.

When should the charger be replaced?

• If the charger still has no output or unstable output after completing the above troubleshooting steps (the output voltage is zero or fluctuates greatly after multiple tests).
• The charger has obvious physical damage (cracked casing, burning, water damage, fan failure) and the repair cost is close to or exceeds the replacement cost.
• The charger frequently overheats, triggers protection mechanisms repeatedly, and cannot be restored to reliable operation even after manufacturer or professional repair.
• Replacement should also be considered when there is a significant age gap between the charger and the vehicle/battery, or when older models are discontinued or incompatible with modern BMS.

Three criteria for choosing a charger: 1) Voltage and current matching: The charger’s output voltage must match the battery pack’s nominal voltage, and the output current (A) should match the battery manufacturer’s recommended charging rate (too high or too low is unsuitable). 2) Battery/BMS compatibility: Confirm that the charger supports battery chemistry types (lead-acid/lithium, etc.) and can communicate with the vehicle’s BMS or has recognized protection logic. Overcharge, short circuit, over-temperature, and low-temperature protection functions are more reliable. 3) Quality and certification: Choose products with safety certifications (such as CE/UL, etc.) and products from brands or suppliers with after-sales service and warranties; pay attention to the protection rating (IP), heat dissipation design, and usage scenario (indoor/outdoor).

If needed, I can help you determine if the charger is compatible based on your vehicle model or battery specifications and provide several recommended options. Would you like to send me your vehicle model/battery information?