So you managed to install CyanogenMod 11 on your phone. Very good, till you realize that the battery just lasts 12 hours.
Nothing to worry about, as CyanogenMod has provided features that can help conserve the battery life once you activate the Performance menu.
To activate Performance Menu, go to
Settings->About Phone. Look for the
Build Number and press on it 7 times. It grants Developer Access.
Once that is done, the Performance menu option becomes visible on the phone in
Settings->Performance and in
Performance Profile, choose
Balanced. Next Select
Processor and in
CPU governor, choose
CONSERVATIVE. Check the option that says
Set on boot. This will be enabled each time the phone is booted.