Xperia XL - only works when plugged in
My Sony ZL works now once is plugged in to a power outlet, however once unplugged dies, instantly,
Replace the battery. Even if the phone says that there is a high quantity of battery life available, the phone draws too great of a charge and instantly shuts down.
In the next 2 or 3 days, I will have a complete battery replacement guide for the ZL, and you also may want to re-file this question under the proper title.
Even if you had a different Sony phone, there seem to be a number with this same problem.
The guide is now active, view it at the following link: