iPhone XS battery health

Replacing the battery will help, but it's not certain that Apple will replace batteries on demand any more. During the promotional battery replacement service ($29 in the United States) Apple was replacing any battery on eligible iPhone models on demand, but only once without the replaced battery being under 80% battery health. Newer reports are that Apple is going back their previous requirement that they will only replace a battery with a specific defect or under 80%.

As for 90% - I wouldn't consider that unusual. The rating is for 500 cycles to 80%. It's a simplification, but that's a linear 1% decline for every 25 charge cycles. With that simplification, it's 250 cycles to 90%. That's certainly possible in 8 months if it's used. Also - there's a distribution of outcomes, so some batteries might decline faster and some slower for any number of reasons, including just randomness.

reegan6 wrote:

Alright thanks! Do u have any tips on keeping a good battery?

Not really. You can read up on all the things that cause batteries to lose capacity faster. In particular, overheating and allowing "deep discharge" (**below** the 0% floor). Apple specifically suggests taking a device out of a case while charging because it might trap heat. There are all these little things that affect battery longevity, but overall they have to be balanced between utility/convenience and that battery longevity.

If you really want a phone battery to last nearly forever, the way to do it would be to keep it hooked up to a power supply almost all the time such that the battery isn't used much. Some people use charging cases or have a cable leading to a USB power pack. My wife might have a cable leading to the USB battery pack in her purse. I've seen a few people who do this while they're putting off getting a new battery.