How To Determine Your Battery Life
For iPhone 6 and later, you can find information on battery health in Settings > Battery > Battery Health. Here you will see the maximum capacity your battery is functioning on & it's peak performance capabilities
The lithium-ion battery in your Apple device will start out functioning at 100% maximum capacity. Charge cycles – which Apple defines as using your battery to 50% power, charging it to 100% power, and then using it to 50% power again – will deplete the lifespan of your battery. A healthy lithium-ion battery will function at 80% maximum capacity and above. Apple recommends replacing your battery once it gets below this point.
Android phones provide some information about the lifespan of your phone battery. To access the information you can dial *#*#4636#*#* and select Battery Information to view your device’s battery status. There are apps such as AccuBattery that you can download to learn more. Once downloaded, you will have to charge your device to access that information.
When to Get a Battery Replacement
Another factor that may have you leaning toward smartphone battery replacement is decreased functionality of the phone itself. Many iPhone users have experienced unexpected shutdowns, extended loading times for apps, and failure to operate unless plugged into the charger.
Current iPhone and Android operating systems can provide some hints to warn you of the demise of your battery that may prepare you for the ultimate decision about what to do. Things you can look out for is if your phone drains faster than in the past, if your phone is slower to power up. The biggest thing to look for if you are worried about battery issues is if your phone never powers up to 100%. Other key things to look out for is if your phone shuts down unexpectedly or will not run unless it is plugged into the charger
It's okay to be unsure when making a decision like this. We can answer any question that you may have regarding batteries.