I'm still looking for the biggest battery that can fit inside the Maestro battery compartment. The Mogix and the Polanfo fit nicely but don't utilize all of the compartment. I thought that the Puridea S3 was the answer but its thickness doesn't quite make it leaving the battery door slightly bulging even after removing the vinyl dot in the base of the compartment. Of course any battery must leave room to put the USB connector on.
Any other battery experiences?