battery charger not charging

The most common cause is poor contact of the charger or battery (corrosion or loosening of the plug/clamp), which results in an unstable charging current input to the battery.

Check items in order of easiest to check to hardest to check (checklist format):

1) No indicator light on site or charger not working at all

Problem → No lights/indicators are displayed after the charger is plugged in; there is absolutely no response.
Possible causes → No power in the socket/circuit breaker tripped, charger power switch not turned on, charger power cord damaged or plug has poor contact.
Solution → Try a known working outlet or use a test pen/multimeter to confirm there is power; check and turn on the circuit breaker in the distribution box; try a different power cord or plug the plug in fully and test by shaking; ensure the charger switch is in the “on” position.
Precautions → Exercise caution when working with live electrical equipment; unplug the charger before using tools; do not use power cords with damaged insulation.
2) The charger has an indicator light but is not supplying power to the battery or the charging is unstable (plug/wiring problem).

Symptom → The charger indicator is normal, but there is no voltage at the battery terminals or the voltage is intermittent, and the charging current is extremely low.
Possible causes → Poor contact of battery clips/plugs, wire corrosion, contact surface oxidation, reversed wire polarity, or poor contact of multi-pin connectors.
Solution → After power off, clean the electrodes and clips (use sandpaper or a metal brush to remove rust), tighten screws, replace damaged wires or connectors; confirm that the polarity/wiring direction is correct; re-insert the multi-pin connector and apply contact protectant.
Precautions → Disconnect all connections before cleaning to avoid short circuits; be aware of the risk of sparks when the clips come into contact with exposed metal.
3) Triggered by the fuse or the charger’s internal protector.

Symptom → The charger suddenly stops working, the indicator light turns red or flashes, and the charger cannot be started but is otherwise undamaged.
Possible causes: blown input or output fuse, internal overcurrent/overtemperature protection tripped, circuit breaker in the distribution box tripped.
Solution → Locate and replace the external fuse or the fuse inside the charger (using the same model as the original); check for a persistent short circuit causing the fuse to blow again.
Precautions → Replace only with fuses of the same current/type; frequent blowing indicates a deeper fault, do not repeatedly replace with larger fuses.
4) The AC power supply voltage is incompatible with the charger (voltage mismatch).

Symptoms → The charger fails to power on or trips the circuit breaker quickly after powering on; the charger’s nominal input voltage differs from the actual voltage at the site.
Possible causes: The charger is rated for 110/120V but the power supply is 220/240V (or vice versa); the on-site voltage is unstable or there is a phase loss.
Solution → Check the input specifications on the charger’s nameplate and measure the actual supply voltage with a multimeter; if necessary, replace with a charger that matches the voltage or use a transformer/modify the circuit (to be done by a professional electrician).
Precautions → Do not connect a rated 110V charger directly to a 220V power supply; electrical modifications should be handled by a certified electrician.
5) Low temperature protection or battery management system (BMS) intervention protection.

Symptom → The charger is connected but the battery does not accept current; the charger displays “Charging prohibited” or flashes an error code; this is especially noticeable in low-temperature environments.
Possible cause → The BMS detects that the battery temperature is too low or the voltage is too low/too high/unbalanced, and automatically disconnects charging (low temperature protection/over-discharge protection/abnormal cell voltage).
Solution → Move the battery to a warm environment to allow it to warm up to the allowable charging temperature; check the BMS status lights/error codes; for lead-acid batteries, perform equalization/activation charging; for lithium batteries, reset according to the BMS instructions or use the manufacturer’s tools to remove protection.
Important Notes → Do not attempt to bypass the BMS or force charging; both low-temperature charging and forced charging can damage the battery or pose safety risks.
6) Abnormal charger output voltage/current (charger aging or malfunction)

Symptom → The charger shows it is charging, but the output voltage is abnormal (too low or too high), or the output current is insufficient or unstable.
Possible causes → Aging of internal rectifier/filter/control components, temperature control failure, or damage to the power module.
Solution → Use a multimeter to measure the DC voltage and no-load/load current at the charger’s output terminals and compare them with the nameplate specifications. If there is a significant discrepancy, contact the manufacturer for repair or replacement of the charger.
Precautions → Ensure correct wiring and polarity during measurement; there is a risk of electric shock from high-voltage parts, do not disassemble if you are not a professional.
7) Problems with the battery itself (unbalanced cells, high internal resistance, battery damage)

Symptoms: Charger is working but battery voltage is low; battery capacity is extremely low after full charge; voltage of one battery cell is abnormally low.
Possible causes → Individual cell failure (aging, sulfation, increased internal resistance), battery pack imbalance, open circuit or short circuit in individual cells.
Solution → Measure the voltage and specific gravity (lead-acid) of each battery/cell separately; perform a discharge test or internal resistance test; try surf charging/equalization charging for lead-acid batteries; consider replacing irreparable cells or battery packs.
Precautions → When replacing individual batteries or cells, ensure they are of the same specifications; replacement or repair of lithium battery packs must be performed by the manufacturer or a professional organization.
8) Internal circuitry or firmware malfunction in the charger (most difficult to diagnose)

Symptoms → Unstable charger behavior, inconsistency between indicator light and actual output, overheating or unusual odor, complex error codes.
Possible causes → Damage to the control board, thermal fuse, transformer, or firmware; ambiguity between components due to aging.
Solution → Send the charger to an authorized service center for repair or replacement; if under warranty, contact the manufacturer for a claim or return for repair; if you choose to repair it yourself, first assess the cost before deciding whether to replace the entire unit or the module.
Precautions → The charger contains high-voltage components; do not disassemble it unless you are a professional. Do not open the box during the warranty period to avoid voiding the warranty.
When should the charger be replaced?

If the above basic troubleshooting (power supply, connectors, fuses, voltage matching, BMS, measurement output) still fails to produce normal output or exhibits unstable performance;
The charger frequently triggers protection, overheats internally, and emits a burning smell or smoke.
The charger has been used for many years (e.g., beyond the manufacturer’s recommended lifespan, commonly 5–10 years) and requires frequent repairs, with repair costs approaching or exceeding the cost of purchasing a new device.
Three criteria for choosing a charger: 1) Compatibility and charging strategy: The output voltage/current should be fully matched to the vehicle’s battery type (lead-acid/AGM/deep cycle/lithium iron phosphate, etc.) and voltage level, supporting appropriate charging curves (constant current-constant voltage, equalization/regeneration/temperature compensation, or able to communicate with the BMS). 2) Safety and certification: It should have overcurrent, overvoltage, reverse connection, short circuit, and overtemperature protection, as well as low-temperature charging prohibition functions, and have locally recognized safety certifications (such as CE/UL or local mandatory certifications); the protection rating (IP) and heat dissipation design should be suitable for the golf cart’s operating environment. 3) Practicality and service: Sufficient charging current to meet charging speed requirements (neither too low to cause slow charging nor too high to avoid battery damage), the interface/plug should be compatible with the golf cart or easily replaceable, and the brand should have good after-sales service and available spare parts/technical support.