There is a thread discussing this problem where the pronto shows a discharged battery but it is not the battery, unfortunately I can't find it again.
They were talking about a "cold solder joint" and because I have the same problem with my TSU6000 I opened it up and looked for a cold solder join in witch I have plenty of experience how to find it and how to solder it properly, I found nothing that looked bad, no one said where the cold solder join was, it might be in the battery or in the charger.
If any one can point out the thread I will appreciate it
Don't buy a charger before you read this thread and get some help.