your battery is in need of conditioning, or else replacement. they all go like this after a while. if you want, you could take a 12V, 5W bulb for a car rear light or interior light, and connect it across the two outer contacts on the battery (the ones with + and - markings over them) . leave the bulb connected until it goes out (to flatten battery completely) . then charge up fully in the phone. repeat a couple of times, and the battery should be good as new. If none of this makes sense, get a new battery, or a new phone with lithium battery e.g. 3510. you may need to solder wires to the bulb, or else get a holder with wires.
Owen.
Owen, August 2004