|"time to try a new battery."|
Laptop main batteries usually work as they should for a year or so, then they begin to rapidly deteriorate. From what I've seen, by two years they cannot be charged to anywhere near their full capacity, and it gets worse after that.
They often develop internal shorts when they are older. If the battery gets HOT rather than just warm after you have attempted to charge it for at least a half hour, or after you have been using the laptop for a while with the AC adapter plugged in, it's definitely internally shorted and you must replace it. Internally shorted batteries getting too hot have been known to cause the laptop to catch on fire.
If your battery is NOT old, or in any case you could try this.....
HP Notebook PCs - Calibrating the Notebook Battery in Microsoft Windows 98, ME, XP, and 2000
For Vista and Windows 7:
Calibrating the Notebook Battery
NOTE that if you use the laptop on just the battery a lot and it's important to you to have a longer run time, SOME HP and Compaq notebooks have the option of you installing a battery that has about twice the wattage capacity / run time as the standard capacity one it came with.
It sticks out of the bottom of battery compartment a bit such that the back of your laptop rests on the battery case, rather than it sitting flat on the computer base, and that tilts the top of laptop's base slightly towards you.
If you wouldn't mind that, usually if the ~2X capacity battery model fits, it's listed in the parts list for your model.
Scroll down a bit.
Look for the similar label on the outside of your computer.
The specific model number - that's at the end of the first line.
The Product number - that's on the third line.
Use one of those to search with there.
Don't type the # and the characters after that in the Product "number" .
You DO NOT have to buy a HP or Compaq brand battery - you just need one that is compatible with your notebook model. Use the HP part number of the battery or your specific notebook model to search for the correct battery.
There are lots of clone batteries on the web that have the same 1 year warranty that are much cheaper.