@waseeq I had the same thing happen to mine. It's caused by one of the cells of the battery being drained, the charger/balancer doesn't "recognize" it. What I did was take a AA 1.5V battery that had a two wire connector hooked to it and stuck the two wires in each hole on the end. I then hooked a volt meter to two wires and stuck the ends of those into the prongs of the battery which plug right into the drone (it read like 7mV). Where the charger plugs in with a three wire connector, I put two wires sticking out of the positive and the neutral. You can tell which is which if you take the battery out of its case and look in the inside at the connector. I took the two wires from the 2.5V battery and held them against the two wires coming out of drone 7.4V battery, held it there for about 30 seconds or so, watched the volt meter slowly rise and then just plugged it into the battery charger/balancer. It forced the battery to give a "recognizable" voltage to the charger. All good now.... ;)