This is my second touch pro 2, each has had the same problem. The battery goes dead, then the phone freezes and now the batter goes dead after 3 hours unhooked from a power source. I am locking the...
The batteries in those devices are Li-Ion battery (look it up on wikipedia, if you want chemical details). They are VERY sensitive to deep discharging.
They are composed of several cells - and even one deep-discharge can fry at least one. In that case, polarity in this particular cell drops and can even be reversed, rendering the battery useless.
That is why all phones switch themselves off way before that occurs - in theory. If the phone hangs, it cannot switch itself off and abovesaid happens.
So what you can do: First, get a new battery. Yours is bad. They are not expensive at amazon or similar.
a) Prevent freezes. HTC Touch Pro 2's are not know to freeze out of blue sky (and mine rarely did), so I guess you keep on using an application that crashes you device. I suggest installing your apps one by one to see, which causes the crash. Meanwhile, rely on b).
b) Prevent deep-discharging. Keep it charged above 50% all the time until you are sure to get no more crashes. It will not hurt the battery to be charged often and only marginally to have that much capacity constantly.