Chosen Solution
My iPhone 6s has a horrible battery life, it would be on 80% then drop down to 16%, then just die, but if I put it on charge it will come on and read 45%. My phone also keeps freezing then turning itself off, then showing the screen where it needs to be charged, then when I put the charger in I’d leave it a while and it still wont turn on unless it has fully charged. The only time I don’t have problems with it, is if it is on charge all the time.
Battery gone bad. Needs to be replaced. If I recall correctly apple are doing battery replacements for 6 and higher for about $40. You can buy a replacement battery from iFixit here: iPhone 6s Battery Here is a guide to replace the battery: iPhone 6s Battery Replacement
