Battery failure, including short circuit, open circuit, single battery lagging behind;
Charger failure, component damage, etc.
Circuit failure, poor contact of charger plug, poor contact of battery series circuit.
Troubleshooting:
Charger and circuit inspection: insert the charger into the charging hole without connecting the 220V power supply. See if the charger indicator light is displayed. Not shown, depending on whether the connection between the battery terminal and the charging hole is broken. The connection is good. That's the problem with the charger. There is a display, and then connect 220V AC to see if the charging display is charging normally. It is the charger itself that is not charging normally. If the monitor can be charged normally, there is something wrong with the battery.
Battery test: After the battery pack is removed, test the capacity of a single battery to see the actual capacity of each battery in the battery pack. If the capacity varies greatly, or some batteries can't be discharged, the whole battery can't be used any more. If it is within the warranty period, you can ask for after-sales service.