yeah i'm afraid there is not much you can do for the battery on the stock system. Some people have seen great amounts of time rooted. I use my phone a lot during the day so I'm lucky if my battery last for 8 hours period.The battery is one of the negatives of this phone. I personally think Sprint was in to big of a rush to put the phone out and some very basic things were not really thought out.
for what it's worth, i can tell you that i have 0 battery problems now that my phone is rooted and i was absolutely furious when i first got the phone. same physical battery, night and day difference.
while the battery is fairly mediocre the real problem is that out of the box the phone is great but the battery it's atrocious...
in lieu of rooting:
turn off radios you're not using - especially 4g and gps, both of which will suck up battery at an unbelievable rate.
If you are using gps, get a car charger.
i use wifi over 3g but only to my preferred networks, ie home and work.
don't just let it search endlessly for wifi networks that arent there or worse, bad connections.
turn down brightness
turn down screen timeout time
avoid fancy cpu-sucking animation screens, backgrounds, themes and screensavers.
avoid task killers
move apps to your sdcard if possible
turn OFF push. push is a great idea at first - but it's not necessary. unless you're some power day-trader, polling every 5-15 minutes is probably fine. do you really need to be reading your email while the person who sent it to you still has his finger on the send button?
push kills battery and is, in my opinion, a gimmick - at least with today's battery technology.
technically i use push, but i also use an app called Green Power Premium which turns everything off when not in use and then connects and syncs periodically.
check what accounts your phone is syncing. do you need a stock ticker on your phone? Do you need the weather? it is nice to have, but how often do you want it updated? do you need the news?
is your phone accessing other accounts - like social media? facebook, twitter etc all take power and you need to decide how often you want them doing this.
chances are you'll learn as you go - i will say many people were pretty PO'ed about the batteries
finally - since this is a used phone, your battery problem could be a simple battery calibration issue. there are a million things out on the web about "calibrating" your battery by some variation of charging and running it down but since you do not have superuser access the only way that i know of for sure to reset the battery stats is to do a factory restore. since you just got the phone you probably don't have much on there but you can back up what you do have (files on the SDCARD such as pictures, songs, videos etc don't need to be wiped) do a factory reset and that could fix some problems. couldn't hurt.
hope all of this helps, good luck!
