DISCLAIMER:
YOU MUST BE ROOTED 
Some users, when flashing new ROMs,
have noticed that their battery life goes
down a little bit. With just a simple
wipe of the battery stats file, though,
you can get your battery back up and
running to its full capacity.
The battery stats file basically tells
your phone how much battery it has
left. The problem is, sometimes this
file can get a little out of whack and
tell your phone it' s fully charged when
it isn't done charging yet—so your
phone will charge to, say, only 93%
instead of 100% before stopping. If
you're rooted and running
ClockworkMod recovery (which most
root users are), you can wipe the
battery stats, giving you a fresh slate
and allowing your battery to more
accurately judge its fullest potential.
To wipe the stats file:
1) fully charge your device, until your
home screen says "Charged" .
Reboot into recovery mode.
2) When you reboot into
ClockworkMod, head to Advanced
> Wipe Battery Stats and hit Yes.
When it's done, go back to
ClockworkMod's main menu and
reboot your phone.
3) After doing this, let your battery
die completely before charging it
up again (you can use your phone
as normal, just don't charge it
until it dies). This will help re-
calibrate it.
I've tested this myself and, while it's
hard to judge what it' s done to my
battery life (I already get pretty
rocking battery life on my Mmx a70), I
haven't seen any adverse effects, so it's
worth a shot if your battery life is
killing you. I'd note that you probably
don't want to do this too often—that
can't be good for your battery. The
general consensus is to do it every
time you flash a completely new ROM.
YOU CAN ALWAYS HIT THANKS
[TUT] Fix battery drain issue on ANY Rom
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