Touch Diamond users who are deperately asking for an extended battery option will be able to buy the battery soon. Expansys in UK has just put up a pre-order page of the HTC Touch Diamond Extended Battery, comes with a back cover to fit the bigger battery.
This should be the official extended battery offer from HTC, according to the retail packaging and it has a model number BP E270 on it. The original battery is BP S270, which is a 900 mAh battery. With the new battery, you will be getting a total of 1340 mAh. The thickness of the HTC Touch Diamond body should be increase a little with the new back cover replaced.
Expansys has put it up for pre-order at 80 USD a piece at the moment.
