Manually Stop Battery from Charging.

I have Compaq presario v6604au notebook and i have got a battery issue.

Since i bought this notebook nearly 18 months ago as a desktop replacement
so it is always plugged in to the power supply and now it has been showing its adverse effects.

My battery life has diminished to nearly 50% of original.

so my question is, as i have stated above can i manually stop my battery from charging even if its plugged in and charge it whenever i want except from removing my battery because it serves as my UPS.

Thanks in advance.

 

Ya I know that battery stops charging after it has completely charged but the problem with my battery is that it has stuck up at 89% and is not going above as a result battery never stops charging.

That is why i want to know how can i stop battery charging manually at any point when i want.

For ex.Most Lenovo-IBM, Dell and acer notebooks have a their vendor based software to stop battery from charging at any point set by the user(Thinkvantage power manager, Dell control point power mangement, Acer epower management).

I have even tried messing up with the circuit, and i was successfull in resetting battery usage data stored in the battery eeprom and i got it to charge to 100% but that lasted only for about 2 days than once it went below 10% it didn't charge to 100% it is again stuck up at 89%.

So my point is that if i could stop the battery to charge as soon as it reaches 80% i could get nearly another 6 months to buy a new 12 cell battery for my notebook.

Any help would be great

 

I am actually using Vista.