When I charge ():

- at first, only the red indicator glows;
- after about 6 hours of charging, the battery will be about 80% charged, the red indicator will stay on but the green indicator will come on as well;
- after another 6 hours of charging, the red indicator will go out, leaving the green indicator on by itself and the battery almost completely charged.

If you want to top up the battery completely, another 6 hours of charging is required.

One further possibility - is there any chance that your battery is one of these after-market lithium ion replacements, that require a different charger: