1. Downloaded cm-9-20121209-NIGHTLY-galaxys2.zip (verified MD5 checksum 4b133e775ca7d48b7d5a970b4cd69e41)
2. Reboot into Recovery and created backup.
3. Select "choose zip from internal sdcard"
4. Flashed cm-9-20121209-NIGHTLY-galaxys2.zip
5. wipe cache partition.
6. advanced > Wipe Dalvik Cache.
7. Reboot.
Battery dropped from 51% to 13%???
