Why is my battery health reducing

Apple stopped selling iPhone 11 a year ago and it was released in 2019. So your phone could be as young as one year, or as old as 4 years.

Battery Health declines with every full cycle battery charge. A drop of 1% per month in Battery Health is considered completely normal. You don't suggest what your Battery Health is, but it will continue to decline as that's what batteries do. ALL BATTERIES. And when or if your Battery Health declines to 80% or less, it will be time to pay Apple to put a new battery in your iPhone.

Bottom line: There is NO WAY to stop Battery Health decline.

Everything I wrote is true for any cell phone. iPhone 12 Pro Max was discontinued 3 years ago. So your phone has to be at least 3 years old.

What is your current Battery Health? It would not be unusual for a 3 year old iPhone to ready for a new battery and for its health to be below 80%.

Dimchi wrote:

In the past month it’s dropped by 3%

Battery Health decline is not linear. It may stay steady for a while, then drop a few points. You still have not answered my question. What is the current Battery Health on your phone? If it's not below 80%, your phone is fine.

Dimchi Said:

"Why is my battery health reducing: My battery health has been dropping significantly what’s the cause"

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Knowing the Cause for Battery Health Drain:

You Can't: Unfortunately, there is no way to determine why, nor when, then Battery Health decreased, making it all a matter of speculation.

How old is your device?