What type of battery is this - NiCd or NiMh?
If it is a NiMh it needs a form charge.
That is a C/10, 300 mAh, charge for 16 hours on a non-peaking charger.
Then cycle and see what you get.
If you do not have a non-peaking charger then cycling up to 10 times may solve the problem.
I suggest tracking each charge to ensure the battery is improving.
I hope this helps.
Good Luck,
KW_Counter