Is iPhone 11 battery health degradation normal?

It is actually better than normal if using your original battery. That phone was only expected to last 500 charge cycles before requiring Battery Replacement when the health drops below 80%. Most of those devices have already needed 1 replacement by now, so if you are on your original battery you have gotten far more use than most others by now, many have needed to have had 2 replacements.

If you are not using the original battery, then you must determine where was the last location the battery was replaced. If it was not done by Apple or Authorized Apple Seller, then you would most likely have a third party battery installed and you may certainly see unexpected results and the battery could fail prematurely or not be able to meet the power demands.

As for drop in Battery Health, it is not linear meaning some months may not drop at all and other months will drop more. The battery estimates are only performed when the phone is allowed to charge to 100%, so users that remove it from the charger early will not see any updates until they forget and see a larger than expected drop. Even when using a Charge Limit, the phone will charge on its own to 100% to update its battery estimates.

boitumelo213 wrote:

My iPhone 11 was on 92% on the 28 august today 21 October it’s on 85% is it normal?

You're referring an iPhone which was originally released in September 2019, 7 years ago and fully discontinued in 2022. So your phone is anywhere from 4+ years to 7+ years old. If it has the original battery, a battery health of 85% is actually outstandingly good. When its health dips to 80%, it will be time to pay Apple to replace the battery or upgrade to a newer iPhone as your phone is from circa 2019 and a lot has changed since then.