Diagnosis: Bicycle battery charger not working

IS MY BATTERY CHARGER DEFECTIVE?

Is your bike battery refusing to charge, or not charging fully? The charger may be defective or malfunctioning. The following are possible causes:

1) Poor contact between the plug and the charging port
This occurs when the charger plug does not make proper contact with the e-bike battery’s charging port. The light on the charger remains green or jumps (at the slightest movement) from red back to green before the battery is fully charged. This problem occurs more frequently with 2-pin plug connections, such as those with an RCA plug. Through use, the RCA plug can become somewhat “stretched,” causing contact with the battery’s charging port to be easily lost.
→ use pliers to slightly reshape the charger’s RCA plug just enough to ensure it makes good contact with the socket on the e-bike battery.

2) The battery is charging, but not fully
Sometimes the charger does charge, but only to, for example, 60 or 70% of its maximum capacity.
→ A fully charged (36 or 37V battery) measures approximately 42 volts between the terminals. If the charger stops and the battery only measures 36 volts, for example, the charger may not be working properly. The best way to test this is to connect another charger after your own charger has stopped charging.

3) The charger is defective
If the LED light does not illuminate when the charger is connected to the mains, this could indicate a defective charger. However, if this light does not turn red when the battery is (partially) empty, it could also indicate a defective charger.
→ It is best to have the charger checked by an expert.