1) is the battery fully charged when you think it's done charging.
2) it could be the charger, if it's a 6 or 12 V charger and not working right you may be able to use a charger from a RC car or airplane, not the tiny one but one that you can control the output with.
If you know someone that flies(crashes) RC or a hobby shop see if you can use one. many shops service these things and will have a charger on the bench.