How to change battery in iPhone? - Apple iPhone 4S

what is your problem exactly. your iphone wont charge fully at what percentage it stop like 90 %.. it may possible that your battery one or two cell not working and that is why it want able to fully change. here is how to do ipad iphone troubleshooting. try to restore iphone to latest version of ios 11. remove your battery then clean connector point of your battery and then reinsert battery.
check your iphone with other battery and then check whether it fully charge or not. also
http://ipodtips-tricks.blogspot.com/2017/09/ipad-iphone-troubleshooting-guide.html

This could be due to a lot of apps and services running in the background, when double pressing your home button, are there any apps open?

You can replace it with an aftermarket battery. That takes opening the case and a bunch of fiddling around inside .. If you are good with tools and have a lot of patience then go for it .. look at ifixit.com or iphone4parts.com for the stuff needed .. Otherwise .. Get an external battery case like a mophie or find a local iphone repair place and pay them to do it for you..

Links:
iFixit The free repair manual iFixit iPhone4Parts Custom Aftermarket Parts for iPhone and iPad

First, try to charge it again, if still not working get a new battery or your friend iPhone battery for check up your iPhone.
Start your iPhone with new battery and if still your phone not working than restore your iPhone by this tutorial http://support.apple.com/kb/HT1414 and need any technical help follow Apple Customer Service .

you cant remove that back like you can on the iphone 4/4s.. you have to remove the screen then all internals.. you can change the glass bit on the back of the phone though they are on held in be sticky tape

The iPhone 4 has a limited number of charging cycles. The battery in the iPhone 4 is a older type of battery that does not keep well depending on the environment you live in. iPhone 4 is in "end of life" status with Apple and is no longer provides support. There is many cellular stores that will change the battery for $25. The replacement battery's are often better than the ones provided by Apple.

Hi,

please refer to the video to check/change the battery:

http://www.youtube.com/watch?v=qAy3xgdci4s

http://www.ezcomputerhelp.org/how-to-replace-the-iphone-4-battery/

Thanks,

E-ware

Its really simple, you need a buy a replacement battery from an online vendor and also a repair kit (probably from ifixit, they are best in the business) and follow the video and instructions on how to replace the battery

http://www.ifixit.com/iPhone-Parts/iPhone-3G-Replacement-Battery/IF137-002

iPhone has an internal rechargeable battery. The iPhone battery isn't user replaceable; it can
only be replaced by an authorized service provider. For more information, go to
www.apple.com/support/iphone/service/battery.

My iphone frooze until the battery drained. now i charged it and i can't turn it on... i don't know