Here is a quick post on how to resolve the “Battery cannot be charged. You must use a Sony Ericsson battery.” message when connecting a Sony Ericsson to the charger.
First you will need the Sony Ericsson DCU-60 data cable, I purchased this from eBay for $2 including worldwide shipping.
Secondly, download the Sony Ericsson Update Service software.
Once the cable arrives, connect it to your phone and run the Update Service software, most likely you will receive a phone is already updated message, ignore that and continue to update the software, after a large download and install follow the prompts to update the software.
That should be all that is needed to resolve Battery cannot be charged issue.