Sometimes my Xperia play battery will last almost 2 days. Other times it will only last 4 hours?

as is 99% of the time , all USP on earth
the batteries are no good, now, or the lugs not clean and tight.
RIP all old battries,
you do know too that all batteries as you use them Amp./hr rating s drop in run time ,right>? less RUN TIME< on ALL UPS on earth./

How old is your controller, maybe your battery is dying. Try opening your controller and replace it.

Apps and services in the background drain your phone even while in standby mode. Turning off your 3G or 4G connection will deprive you of the internet but it will still permit you to get phone calls. Meanwhile, you are not having apps such as Google constantly draining your power in the background. And they are, even in standby mode. Charge your phone frequently to help preserve battery life.

The charging base is loose you have to replace.
It will work.

Hi,
As far as I discover ,up to now, the battery life of the Sony Ericsson Xperia X10 smartphone has been kept under wraps. The official product page is just left blank under the battery performance section. However, with the news of the handset launching in Japan, the official SE Japan site does reveal this juicy information. Given its 1GHz Snapdragon chipset and 4-inch screen, I wasn't putting too much hope in decent battery life, but it's looking reasonably okay.
Talktime with 3G networks should last for 4 hours and 50 minutes, whilst a 3G standby time of 200 hours is quoted. Obviously official numbers are always inflated, but at least you'll hopefully be able to get a good days use out of it before having to re-charge.
Just for your own test;
On the dialler press * #*#4636#*# * and under battery history make sure that your phone is sleeping when you are not using it. (Time spent not sleeping)
If its at 100% then an app you've installed is preventing your phone from sleeping. I think the latest firmware fixes the issue
Please switched off the auto screen brightness and set it manually at about 75% which should shorten the battery life but so far no.
A free program called TaskKiller will definetely help to close the .apps draining battery...
Pls read the articles on the URL below for more info and Tips..
Hope this helps! Take care and please Remember to rate/vote and give me
4 Thumbs Up for me to continue for Helping out the Community :)
Thanks
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How To Fix The Battery Life On The Sony Ericsson XPERIA X10
http://www.sonyinsider.com/2010/04/13/how-to-fix-the-battery-life-on-the-sony-ericsson-xperia-x10/

The litium battery should last u about 3 and 3 1/2 years.The minium used about 4 1/2 hours a day,about 3 times a month.Tries Websites Amazon.com,Ebay.com should have this Litium battery.

Charging duration does not connect to battery lasting duration in any way.Optimal charging time is 3 to 4 hours.your battery will drain soon if you keep your touchscreen pressed continuously in your jeans pocket.Keep bluetooth switched off. Reduce the brightness of your mobile display. Play music threw headphone rather than using loudspeakers.

try when your not using it putting it into flight mode

if you are running alot of programms and your screan brightness is on full your laptop battery will die fast.
try running one or two programms at a time. this will lenthen your battery time. plus dont leave it charging all the time this will ruin your battery.

It depends on how much talking your doing. The Slvr is known for its low talk-time battery power. My slvr would last about 3 to 4 days on a charge, unless i was talking on it a lot. sometimes i would be charging it every other day. So it really all depends on the talk-time. Invest in a car charger for sure.