Charudatta Galande provided an answer on quora.com to this question.
Read his response at: QUORA.COM
It was interesting to see this unfold as Apple's intention was meant to assist users of older devices to avoid having unwanted shutdowns when the battery was operating at substandard levels. Of course the ambulance chasers saw an opportunity for money for nothing.
The reality is that batteries lose their ability to hold a charge the older they are and after a finite number of recharges. So those seeking damages for a probably undetectable slow down are leeches when in reality, Apple was doping them a favour.
Apple since provided the ability to see the state of the battery and you will be able to choose between changing the battery at a heavily discounted price, allowing the phone to slow down to prevent sudden shutdowns, have an unreliable device or perhaps just get a new phone.
With the current iOS you can check the state of your battery. Go to Settings/Battery/Battery Health. It will give you information about the maximum capacity of your battery. You can also see what is consuming the battery's charge.
See AppleInsider for the full article.
The main factors are:
- Screen brightness
- Weak mobile phone coverage and weak WiFi
- Rogue apps
- Too many notifications