How much will cost for battery replacement..?

Go to this web site for information about how to request battery service for your iPhone: iPhone Battery Repair & Replacement - Apple Support

For cost and availability, enter your model information in the "Get an estimate" box at the bottom. (I will let you do this since the answer will depend upon the country where you are located.)

Is it really time to change your battery? See this excerpt from: Batteries - Maximizing Performance - Apple

"A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge."

Hello ~ Take a look here by clicking on below…

iPhone Battery Repair & Replacement - Apple Support

Scroll down to “ How much does it cost? ” and enter your information for an estimate. You can also set up your repair from the link about as well as below…

Genius Bar Reservation and Apple Support Options - Apple

~Katana-San~