The Ipaq 2215 has a supercap as a temporary backup while you change batteries. It's supposed to give you several minutes grace. As the other poster said, yours is probably done dead.
You could get it replaced, or order the supercap and replace it yourself, but you have to be handy with a soldering iron, as it is soldered to the board.
Or you could get a charging unit for your car.
Failing that, you could get one of these
http://www.thepocketsolution.com/PSI-1173/...ry+Booster.html
That may be your best solution, a little more to carry around with you, but probably worth it.