battery charging not working

The most common cause is usually poor contact of the charging cable or plug, or that the fuse/circuit breaker on the vehicle/charger side has been blown, resulting in the inability to establish a stable charging circuit.

Below is a checklist arranged from easiest to hardest to check, with each step including: phenomenon → possible cause → solution → precautions.

1) Check the charger indicator lights and sound.

• Symptom: When the charger is plugged in, there are no indicator lights, no fan is running, or the indicator lights are flashing abnormally.
• Possible causes: The charger itself has no power supply, an internal malfunction, or a problem with the input power supply.
• Solution: Confirm that the charger plug is correctly inserted into the wall socket and has power; test with a known working power outlet; observe the indicator light status and consult the charger label or instruction manual for its meaning.
• Precautions: Do not disassemble the charger in a humid environment; observe for any burning smell or obvious signs of damage such as bulging.

2) Check the wall/camp power supply (external power source).

• Symptom: Other devices work when the socket is in the home, but the charger does not respond; or the charger works in some sockets but not in others.
• Possible causes: No power to the socket, power switch/delay device not turned on, circuit breaker tripped, or ground/neutral wire problem.
• Solutions: Use other electrical appliances or a multimeter to check if the socket has power; check the circuit breaker/leakage protection in the distribution box; try another socket that you have confirmed is working properly.
• Precautions: Always turn off the power supply and follow safety procedures when inspecting the distribution box; if you suspect a wiring problem, please have it handled by an electrician.

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

• Symptoms: Overheating at the contact point when connected to the battery, loose contact, unstable charging indicator, or intermittent charging.
• Possible causes: Oxidation, corrosion, loosening, or bent pins of plug/socket terminals; poorly tightened wiring terminals.
• Solution: After disconnecting the power, inspect and clean the terminals (lightly brush or use a contact cleaner); tighten the terminal screws; replace severely corroded connectors; when reconnecting, ensure the plug is fully inserted and locked.
• Precautions: Disconnect the charger and battery before operation; avoid touching the terminals with wet hands; if the terminals are severely damaged, replace them with professional parts.

4) Check the fuses/circuit breakers in the vehicle or charger.

• Symptom: The charger is plugged in but there is no output current, or the charging process suddenly disconnects and cannot be restored.
• Possible cause: The vehicle’s main fuse, charger input fuse, or on-board circuit breaker has blown/tripped to protect the wiring or equipment.
• Solution: Check and replace the fuse with one of the same specifications according to the instruction manual; if it is a resettable circuit breaker, disconnect the load first and then reset it; find and eliminate the short circuit or overload that caused the fuse to blow.
• Precautions: Use fuses of the same specifications as the original fuses; do not replace them with fuses with higher current ratings. If fuses blow frequently, find out the root cause before powering on.

5) Measure the battery voltage and check for voltage mismatch (voltage mismatch).

• Symptom: The measured battery terminal voltage does not match the charger’s nominal output voltage, or the charger displays abnormal voltage/current.
• Possible causes: The charger voltage is not compatible with the battery pack’s nominal voltage (e.g., using a 24V charger for a 36V battery), or the individual cells are unbalanced, leading to an abnormal overall voltage.
• Solution: Use a multimeter to measure the voltage at the battery pack terminals and compare it with the nominal voltage of the battery; confirm that the charger model and battery pack voltage are consistent; if the voltage of individual cells are inconsistent, balance or replace the faulty cells.
• Precautions: Ensure safe wiring during measurement to avoid short circuits; different battery chemistry systems (lead-acid, lithium) have different requirements for charging voltage/curves and must be matched.

6) Check BMS protection or undervoltage protection (BMS protection/undervoltage disconnect)

• Symptoms: The charger is connected normally but cannot charge, or the charger displays a “fault” or “obstruction” message; sometimes the vehicle’s display will show “BMS fault” or “charging prohibited”.
• Possible cause: The battery management system (BMS) cuts off the charging output to protect the battery after detecting over-discharge, overheating, overcurrent, abnormal individual cells, or communication abnormalities.
• Solution: Check the BMS error codes using a vehicle or battery fault code reader; address the root cause of the BMS activation (low cell voltage, imbalance, abnormal temperature); some BMS systems can be reset by power-off restart or with professional equipment.
• Precautions: Do not bypass BMS protection at will, as this may cause permanent battery damage or safety risks; professional personnel should reset or replace the BMS when necessary.

7) Low temperature protection (low temperature protection)

• Symptoms: The charger fails to start or its charging performance drops significantly in cold environments; a low-temperature alarm is displayed or the charger cannot charge to the normal voltage.
• Possible causes: Some chargers or BMS automatically disable charging to prevent battery damage when the temperature is below a set level; lead-acid/lithium batteries experience increased internal resistance at low temperatures, leading to charging difficulties.
• Solution: Move the charging location to a warm place or preheat the battery to a safe range (using a battery heating pad or room temperature), and try again after the temperature rises; purchase a charger with low temperature tolerance/temperature compensation function.
• Precautions: Rapid heating of the battery is not recommended (e.g., using an open flame) to avoid sudden temperature changes that could cause internal stress; refer to the safe charging temperature range provided by the battery manufacturer.

8) Charger and battery incompatibility/charger internal malfunction (voltage/current mismatch or device failure)

• Symptoms: The device still does not work after replacing the power supply and terminals, or the charger is aging, overheats abnormally, makes strange noises, or has a burning smell.
• Possible causes: The charger’s output parameters (voltage/current/charging curve) are mismatched with the battery chemistry/voltage; the charger’s internal circuitry or transformer is damaged.
• Solution: Check the charger nameplate parameters against the battery requirements (voltage, maximum charging current, compatible charging curve); replace with a known working charger of the same specifications to rule out equipment malfunction; if the charger is diagnosed as faulty, contact the manufacturer for repair or replacement.
• Precautions: Do not use non-original chargers or chargers with incorrect specifications as long-term replacements; there is a risk of electric shock from the high-voltage components inside the charger, and non-professionals should not disassemble and repair it.

When should the charger be replaced?

• The charger has no output under multiple normal power sources/outlets and has been confirmed not to be a fuse or external problem.
• The charger exhibits signs of damage such as continuous overheating, unusual odor, burning, or bulging.
• Professional testing or replacement experiments have confirmed that the charger output is unstable or the output parameters deviate from the nominal value, affecting battery charging efficiency or safety.
• The charger is aging, frequently malfunctions, or cannot support the requirements of new battery packs (e.g., voltage/communication incompatibility).

Three recommended standards for choosing a charger

1. Voltage and battery chemistry must be perfectly matched: The charger’s nominal output voltage must be consistent with the battery pack’s nominal voltage and correspond to the battery chemistry (lead-acid, AGM, gel, lithium iron phosphate, ternary, etc.) to ensure that the charging curve and termination voltage are correct.
2. The charging current should match the capacity/charging demand and have protection functions: the maximum output current of the charger should match the battery capacity and the manufacturer’s recommended charging rate; it should also have protection functions against overvoltage, overcurrent, short circuit, reverse connection, temperature compensation, and communication with the BMS (if the battery has a BMS).
3. Certification, connector compatibility and after-sales service: Choose products that have passed safety certifications (such as CE/UL, etc.), ensure that the charger connector/wiring harness is compatible with or replaceable with the vehicle interface, and give priority to brands or dealers with good warranties and after-sales support.