why is battery not charging

The most common cause is poor contact between the charger and the battery/wiring harness (loose plug or wiring, oxidation), which prevents the charging circuit from being established.

Troubleshoot in order of easiest to hardest (each step: symptom → possible cause → solution → precautions)

1) Check the charging plug and connector.

• Symptom: No indicator light is displayed after plugging in the charger; the device fails to charge or charges intermittently.
• Possible causes: poor plug contact, oxidized pins, or loose/damaged plug (including inside the charging port).
• Solution: After disconnecting the power, unplug the plug and check for corrosion, burn marks, or foreign objects; clean the contacts with alcohol/contact cleaner and let them dry, then plug it in firmly or replace the damaged plug/socket.
• Precautions: Disconnect the mains power and the vehicle’s main switch before operation to avoid cleaning while the power is on; after cleaning, plug and unplug the switches several times to confirm good contact.

2) Check the fuses and circuit breakers.

• Symptom: The charger does not respond at all or the charger indicator light does not light up.
• Possible causes: blown fuse in the vehicle or charger, tripped vehicle circuit breaker.
• Solution: Refer to the circuit diagram to locate the fuse/circuit breaker and replace it with a fuse of the same specification or reset the circuit breaker; if the fuse blows repeatedly, find the source of the short circuit.
• Precautions: Do not use wires or copper wires that do not meet specifications to replace fuses; if the location is unknown or the fuses are frequently blowing, contact a professional.

3) Check the mains/power socket and power cord.

• Symptom: The charger indicator light is on, but charging is unstable or interrupted, and the charging time is abnormally long.
• Possible causes: Unstable external power supply voltage, poor socket grounding, or damaged power cord.
• Solution: Replace with a reliable power outlet and check if the power supply voltage is stable (use a multimeter to measure); check and replace any damaged power cords; use a voltage regulator if necessary.
• Precautions: Be aware of the risk of electric shock when measuring mains electricity; if necessary, please consult an electrician.

4) Measure the charger output voltage (to check for voltage mismatch).

• Symptom: The charger’s working indicator is normal, but the battery voltage does not change or the charging voltage is abnormal.
• Possible causes: The charger’s output voltage does not match the battery’s nominal voltage; there is an internal output fault or incorrect setting in the charger.
• Solution: Use a multimeter to measure the charger’s output voltage under no-load and load conditions to confirm that it matches the battery pack’s nominal voltage (e.g., a charger outputting approximately 54-58V for a 48V vehicle). If it does not match or has no output, replace or repair the charger.
• Precautions: Avoid short-circuiting metal tools when measuring terminals; ensure the measurement method complies with the charger’s instruction manual.

5) Check the BMS (Battery Management System) and protection actions.

• Symptoms: The charger stops charging quickly after being connected; the charger or meter displays an error code; no current enters the battery during charging.
• Possible causes: The BMS detects an anomaly (overvoltage/undervoltage/overcurrent/short circuit/individual cell imbalance) and cuts off the charging circuit, or communication failure causes the charger to be prohibited from charging.
• Solution: Read the BMS fault codes (some vehicles can use diagnostic tools or instruments to check), and reset the BMS according to the manufacturer’s procedure; for individual cell imbalances, first perform equalization charging or contact a professional to perform individual cell testing and repair.
• Precautions: BMS protection is a normal behavior to protect the battery, and it is not recommended to force the protection to be skipped; please have professionals handle any BMS disassembly, installation, or parameter changes.

6) Low-temperature protection and the influence of ambient temperature (low-temperature protection)

• Symptom: The charger cannot charge or the charging current is extremely low in low-temperature environments, and the charger displays a limit/stop message.
• Possible cause: The battery or charger has built-in low-temperature protection (or the BMS prohibits charging at low temperatures) to prevent electrochemical damage.
• Solution: Move the vehicle or battery to a warm environment to a suitable charging temperature, or use a dedicated charger that supports low-temperature charging mode (if the battery allows).
• Precautions: Do not forcibly increase the charging current at extremely low temperatures; do not directly heat the battery with an open flame or at high temperatures.

7) Damaged or degraded individual battery cells

• Phenomenon: It can accept some charging but cannot be fully charged, the battery life drops sharply, or the voltage drops quickly after charging.
• Possible causes: Some battery cells have high internal resistance, capacity degradation, or are damaged, making them unable to properly accept and retain charge.
• Solution: Perform internal resistance and capacity tests on the battery pack, replace damaged cells or the entire battery pack; if necessary, perform equalization or maintenance charge-discharge.
• Precautions: Battery replacement requires matching specifications (voltage, capacity, chemical system) and professional installation; used batteries must be recycled in accordance with regulations.

8) Internal charger malfunction or communication problem (difficult to repair yourself)

• Symptoms: The charger displays an error code, the charger overheats, the charging process disconnects abnormally, or it cannot communicate with the BMS.
• Possible causes: Faulty charger control board, relay, cooling system, or damaged communication lines (CAN/RS485, etc.).
• Solution: First, try charging with another known working charger to rule out vehicle-side issues; if the charger is confirmed to be faulty, please send it to the factory for inspection or replacement.
• Precautions: Do not attempt to open the high-voltage section of the charger for repair (risk of electric shock); within the warranty period, please contact the manufacturer first.

When should the charger be replaced?

• The charger has no output or the output voltage is consistently abnormal when connected to multiple different power sources/sockets.
• The charger repeatedly exhibits the same fault after repair or emits irreparable high temperatures, smoke, or a burning smell;
• The charger is incompatible with the vehicle’s BMS/voltage, or the charger is old, the manufacturer has discontinued production, and it cannot meet safety standards.

Three criteria for choosing a charger: 1) Voltage and current fully matched and compatible with battery chemistry: Choose a charger with the same nominal voltage as the golf cart battery pack (note the rated output voltage/charging termination voltage), and the charging current should be within the battery’s allowable range. 2) Support for BMS communication and protection functions: Preferably, the charger should support communication with the battery’s BMS or have necessary protection functions (over-temperature, over-voltage, under-voltage, over-current, short circuit, low temperature protection, and equalization function) to ensure charging safety and battery life. 3) Quality and safety certifications, good heat dissipation, and after-sales service: Choose brands with CE/UL certifications, good IP/heat dissipation design, and clear warranty and after-sales channels; durability and after-sales service are more important than simply low price.