Advanced phone customization/Improving battery life

Improving the battery life of your phone is another popular reason of using a custom ROM.

Customizing power management
Custom ROMs often include a greater level of power management options, and you should take some time to find out which setting really suits you best. The procedure for accessing the power management features vary between ROMs. You can also change the phone governors; try with the  or   for a start, though they may impact your performance in return. It depends on your tolerance level.

Using apps
There are apps like Greenify which can be used to aggressively manage battery life, some even without root. Again, you should take the time to find out which app suits you best, and make sure that the settings you apply still allow the apps to sync regularly.

Hardware
Often, the grim reality is that
 * your phone simply has a small battery or uses older, inefficient components
 * your battery has degraded over time.

In both situations, your only options are to
 * add a battery pack or keep spare external batteries
 * replace your phone's battery if you can
 * replace your phone

Unfortunately, all the customizations we did here can only improve your phone by so much; as we said, these techniques are software and can't account for hardware limitations beyond a point.