How may cycles is your battery showing? The 6S was never known for stellar battery life. I had the battery in my backup 6S replaced by Apple exactly a year ago and it’s still showing 98% capacity.. 3rd party batteries are hit or miss as far as quality is concerned.
Here is what coconutBattery reports:
iOS reports 85%, but it’s clearly less than that.
Battery life with a new battery is actually pretty good, but it doesn’t last more than 6 months before the battery starts to deteriorate again.
Apple OEM is the best, there's no other way.
I personally have iFixit battery on my 6s but it's as bad as Apple's, if not worse. I think it's an issue coming from the phone.
And that's a second iFixit battery. So, maybe the better option is to upgrade your phone.
I’d upgrade my phone right now if I had the money. Unfortunately, that’s not the case at this moment.
Even if third party batteries were the same as Apple’s OEM ones, I’d still prefer to buy them at 25€ and replace them myself rather than spending 55€ at the Apple Store. I replaced them at Apple when they were charging 29€, and I’d happily do that again if the price stayed the same.
I can vouch for ReplaceBase. I ordered only back glasses for iPhones and stuff for MacBooks and they were all high quality. I’d trust them for supplying good batteries too.
It’s immensely difficult to find a good battery supplier for iPhones if you are not going the Apple route.
Thanks man, I think I will try their high capacity one. I hope to replace my phone in the first half of 2020 anyway.