lithium battery won’t charge

The most common cause is that the charging circuit is interrupted, usually due to poor plug contact, a blown fuse, or BMS/low temperature protection triggering, which interrupts charging.

Troubleshooting checklist (arranged from easiest to most difficult)

1) Check the charger and mains power supply.

• Symptoms: The charger has no indicator light, the indicator light is not lit, or the charger is completely unresponsive.
• Possible causes: No power to the wall socket/circuit breaker, poor contact in the extension cord or socket, or the charger power switch is not turned on.
• Solution: Plug the charger into a known working outlet, confirm that the home circuit breaker/residual current device has not tripped, and confirm that the charger’s power switch is in the “on” position.
• Precautions: Do not use thin extension cords or inferior sockets to carry high current; disconnect the power supply before plugging or unplugging to avoid electric shock.

2) Check the charging plug and the vehicle socket (poor plug contact).

• Symptoms: The charger displays an error message when plugged in, or the connection is loose or the connector is hot/discolored.
• Possible causes: plug not fully inserted, pin corrosion, lock breakage, or contact carbonization.
• Solution: After powering off, unplug the connector and check the pins/sleeves for corrosion or foreign objects. Clean them (with a dry brush or contact cleaner), then tighten them again and ensure the clips are fully engaged.
• Precautions: Disconnect the power supply before cleaning; do not short-circuit the contacts with metal tools; replace the connector or wiring harness if severely corroded or damaged.

3) Check the fuses/circuit breakers on the vehicle body and charger.

• Symptoms: The charger indicator is abnormal, there is no output after connection or the circuit breaker trips immediately.
• Possible causes: The main fuse in the vehicle body or the fuse inside the charger has burned out, or the circuit breaker has tripped.
• Solution: Locate and replace the fuse (using the same model as the original), and reset the vehicle circuit breaker. If the fuse blows again after replacement, continue to investigate the source of the short circuit.
• Precautions: Do not risk replacing fuses with those of higher specifications; repeated blows indicate an electrical fault and the fuse should be taken out of service and professionally inspected.

4) Check the charger indicator lights/fault codes and output voltage.

• Symptoms: The charger light flashes or displays an error code; the charger does not output current.
• Possible causes: internal charger malfunction, charger detects abnormality at the battery end (such as BMS disconnection).
• Solution: Read the charger manual for the corresponding indicator light/fault code; use a multimeter to measure the charger’s output open-circuit voltage and the voltage when the battery is connected (it should be slightly higher than the battery’s nominal voltage, for example, the charging voltage of a 48V system is usually in the range of 54-58V, depending on the battery specifications).
• Precautions: Pay attention to polarity when measuring; if you are not familiar with electrical work, please ask a professional to measure; do not operate with wet hands or in a damp environment.

5) Measure the total voltage of the battery pack and the voltage of each individual cell (voltage mismatch).

• Symptoms: The charger is connected but the battery does not absorb power, the charging current is 0; or the voltage of some batteries is abnormally high/low.
• Possible causes: The charger’s rated voltage is incompatible with the battery pack (e.g., using a 36V charger to charge a 48V battery), the individual cells in the battery pack are unbalanced, or one cell is severely depleted.
• Solution: Measure the total voltage of the battery pack and measure the voltage of each individual cell (each battery or each string); confirm that the charger model is completely consistent with the battery’s nominal voltage; if there is a large difference between individual cells, equalization is required or professional replacement/repair of the faulty cells is needed.
• Precautions: Take care when measuring each section to avoid short circuits; if the voltage is low enough to fall below the BMS lockout range (over-discharge), do not force it to charge with high current, but first use professional equipment to wake it up/equalize it.

6) Check BMS protection (including low temperature protection/BMS protection)

• Symptoms: The charger is powered on but the current is zero; the charger or vehicle displays a BMS error; it only stops charging at low temperatures.
• Possible causes: The BMS detects excessively low/high voltage, excessively low temperature, or cell imbalance and disconnects the charging relay; low temperature protection prevents charging to avoid battery damage.
• Troubleshooting: Check the error code displayed by the vehicle or charger. If it’s low-temperature protection, move the battery to a warm environment or use a blanket/heater to slowly warm it to the recommended temperature range (usually >0–5°C). If the BMS is disconnected due to cell imbalance, a professional equalizer or repair is required. Some BMSs can be reset by disconnecting the power (disconnect the main negative line for a few minutes and then reconnect it).
• Precautions: Do not use open flames or strong heat (such as direct connection to a dryer) to quickly heat the battery; if BMS errors occur frequently, do not continue to try to reset it roughly, but seek professional diagnosis.

7) Check the compatibility between the charger and the BMS/communication line (voltage/communication incompatibility).

• Symptom: The charger displays “connected” after being connected to the battery, but does not start charging or continues to display an error message.
• Possible causes: The smart charger needs to communicate with the BMS (CAN, signal lines) to allow charging, or the charger’s chemistry/charging profile is incompatible with the battery; the charger’s rated voltage is incorrect.
• Solution: Check the charger specification label (output voltage, current, applicable battery type) to confirm it supports your battery chemistry (e.g., LiFePO4); check that all communication lines are intact; if possible, try testing with an original or known compatible charger.
• Precautions: Do not use non-dedicated chargers with similar but incompatible nominal voltages as long-term substitutes; incorrect charging curves will damage the lithium battery.

8) Check battery health or BMS/relay hardware malfunction (requires professional expertise)

• Symptoms: All external checks are normal, but the battery still won’t charge; battery capacity has decreased significantly or the internal resistance of some battery strings is abnormally high; the charger works normally with healthy batteries.
• Possible causes: battery cell aging or short circuit, damage to the BMS internal relay/control board, or internal wiring breakage.
• Solution: Send the battery to a professional repair shop for unpacking and testing of individual cell voltages, internal resistances, and BMS board status; replace the damaged cells or the entire battery pack according to the report, or repair/replace the BMS.
• Precautions: Disassembling the battery poses risks of electric shock and chemicals. Do not attempt to disassemble the battery pack or solder the battery cells yourself. Choose a qualified repair service and retain the test report.

When should the charger be replaced?

• The charger does not produce any DC output when the AC power supply is confirmed and the connection is correct (the multimeter measures 0V or much lower than the nominal output).
• The charger overheats abnormally, emits smoke, smells burnt, or sparks during operation;
• If the charger continues to report a fault or fails to start charging even after testing with a known good battery, and the charger’s fault indicator does not disappear
  , replace/repair the charger first.

Three recommended criteria for choosing a charger: 1) Voltage fully matches the battery chemistry and supports BMS communication: The charger’s output voltage must be equal to the battery pack’s nominal voltage and be able to communicate with the BMS (if the battery is LiFePO4, choose a charging curve that supports this chemistry and can communicate with the BMS or has relevant configuration). 2) Output current matches the battery’s allowable charging rate: The charger’s rated current should be equal to or slightly lower than the battery manufacturer’s recommended maximum charging current (usually 0.2C–0.5C is safe) to avoid long-term high-rate charging that accelerates aging. 3) Comprehensive protection and certification: Choose a smart charger with overvoltage, overcurrent, short circuit, overtemperature protection and temperature compensation, and prioritize brands with CE/UL or relevant local certifications, a good reputation, and after-sales support.

If you’d like, I can help you verify the charger model or interpret the parameters on the charger label based on your golf cart model or battery specifications (e.g., 36V/48V, LiFePO4, or others).