Ich glaube ich hab das Akku Problem gelöst!

I dont charge the new phone for 8 hours.
Normaly charge too 100% is enough
The easiest way to save power:
1. set a 15 minutes data timeout in both profiles
2. disable 3G Network and turn it on when required
3. disable "show me open networks" in the wireless settings
4. disable wifi, when you have near networks but no access to use
5. set brightness manually (for me 20% is enough)

Ok
but did you put it straight to charge out of the box , or use it to low battery level and then charge?

charge it before use