Apple is offering fixes for battery issues on 6s models.
If you have an iPhone and have been experiencing power issues lately, you might be able to get a free replacement battery for free, courtesy of Apple. After many users complained that their phones had been shutting down unexpectedly after upgrading to the new iOS, the company announced the replacement program. Unfortunately, only a small number of iPhone 6s models are eligible, specifically those that were manufactured between September and October 2015.
To find out if your phone is eligible, you should check your phone’s serial number by looking at the back of your iPhone, or going to Settings>General>About. Next, check the 4th and 5th characters on the phone for one of these: Q3, Q4, Q5, Q6, Q7, Q8, Q9, QC, QD, QF, QG, QH, QJ. You can also go to an Apple store to confirm your phone's eligibility.
If your device is part of the program, you can contact an Apple Authorized Service Provider, Apple Retail Store, or Apple Technical Support to see if same-day battery replacement service is available, or if a replacement will need to be ordered. To prep your phone before you get it fixed, Apple recommends backing it up to ITunes or iCloud, turning off the Find My Phone feature, and erasing data and settings by Settings>General>Reset>Erase all Content and Settings. Also, if your iPhone has a cracked screen, that might affect the repair, so you might need to get that fixed first.