Power it on with the battery only and let it totally discharge. Once it dies, start it up again and just let it die. Just trying to totally empty the battery. Once its totally dead, plug it in and recharge it. Also if there is a calibrate function on that model laptop try that. Don't know much about the Toshiba's or samsungs. Also is there a battery test in the bios?
But like the poster above said, if its older it could just be going bad.