Why iPhone's 15 battery health dropped from 100% to 99% in 1.5 months?

tejakondeti wrote:

Yeah but i used my phone very less and maintained battery optimisation and also 80%. And maintained proper charging.

ihave maintained all these things but it comes 99% within a span of 1.5 month.

And it's going to continue to drop. It may not drop every month, but drop it will, because that's what batteries do. ALL BATTERIES. It doesn't have anything to do with playing games. With every full cycle battery charge, the health of the battery will decline, little by little. You can't stop it. When the battery declines to 80% or less, which it most definitely WILL do one day, it will then be time to pay Apple to replace the battery. Until then, stop worrying about something which is normal and you cannot change.

Your Battery Health is quite normal. The average Apple Battery lasts about 2 years with normal usage. When Battery Health reaches 80%, it will be time to make an appointment at the nearest Apple Store for Battery Replacement. Check this link...

Batteries - Maximizing Performance - Apple

This is normal. There is nothing wrong with your battery.

If you want more proof, make an appointment at the Apple Store to have the battery tested.

The battery health is going to decrease overtime.

1% a month is normal.