Is your battery still alive? Check with a multimeter whether it still outputs 3-4V.
Is the polarity correct? The charger and the battery may have different pinout...
It's possible, that your battery is dead. Btw, most likely you can get the battery locally (altho don't know where you live), or from a proper electronics parts supplier (digikey, farnell, mouser. Or one of the hobby electronics stores).
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