Did the following ever occur to you?
''Apple first reported that many of its iPhone 6S models have issues such as battery charge level abruptly plunging from 50% to 1% or worse, the phone just shuts down completely - only to display a charge level of 20% when they are plugged in again''. Based on our experience with the past 500 over battery related repairs we have done, the issues with battery are not limited to 6s but other models as well. These problems typically fall into the following 4 categories:
Typically, a new lithium - ion battery is made to last 700-800 charges. Over time, the capacity of the battery will reduce. This is because each time the battery charges, the electric current pushes the lithium ions from the battery's cathode to degrade, resulting in some lithium ions unable to reach the anode. This whole cycle causes the battery to lose its capacity.
Apple has admitted that a small number of phones have shut down. Up until 27th July 2016, Apple has sold more than 200 Million iPhone 6s models. Taking 1 percent of the total number sold, it comes to 2 million iPhones with problematic batteries.
iPhone charging IC might be damaged or spoilt which will either lead to fake charging or might not charge the phone. As a result, the battery might take too long to charge the phone or appear dead while charging.
Before iOS 10.2.1, many iPhone 6 and 6s users face issues when the battery charge level abruptly plunges from level 50% to 1%. Another instance is when the phone inexplicitly turns off altogether. However, once charging starts, the battery level recovers to 20%. With the iOS update, we believe that it changes how the battery draws power, avoiding surges that force the device to shut down. Hence, if the issue is persistent, its likely to be the battery or the IC.
In summary, if the issue of short battery life does not improve after the software upgrade, do let us know if we can help you out.
Do check out the 5 Hacks to extend iPhone Battery Life by 50% if you have not done so!