Battery doesn't charge all the way up?

[*^___,^*]

I have an HP computer (with Vista), I bought it about 1 1/2 years ago, and lately I've been noticing that the battery only charges to 22%, then stops and says "Not Charging". I have been using it a lot, so does usage of the computer affect the rate at which the battery deteriorates? How much do batteries for HP's roughly cost?

[Human Helper]

They burn out. You need to buy a replacement and fully charge/discharge it before use. Then only use it when you need the Laptop in battery mode. This will prolong it's life.

They can vary in price, you need to look around. The 2 links below are for UK & US, HP batteries.