The battery is an internal battery, pls replace by professional person or go to repair store. or you could search on Youtube and watch the video to learn how to replace the battery correctly.
*New Lithium Ion batteries must be FULLY CHARGED and FULLY DISCHARGED 2 to 3 times, before being FULLY CONDITIONED. Please remember that a new Lithium-Ion battery’s full performance and longevity is only achieved after 2 to 3 complete charge and discharge cycles. After you go through 2 to 3 cycles, you’ll never have to condition your battery again!
*All talk and standby times are approximate, depending upon carrier’s network settings, signal strength, and features selected. Talk and Standby times will be lower in Analog mode as noted above.