My iPhone 15 Pro Max battery health is rapidly declining

Hi!

1. cost battery replacement:

just looked it up for you and these are the prices for the US (i dont know where you from sorry!)

duration for a battery replacement:

so far as i see a battery replacement in a apple store wouldnt take longer then a day or even will happen the same day (depends on the region)

if you send this on mail to apple it would take up to 2 weeks max! So i suggest to visite a apple store to have the fastest service!

applecare plus cost

as far as iknow you have to pay then, i dont have the support in my region so i sadly couldnt tell if this is the case or not im sorry!

i hope i did help you out a bit!

dhairyaprajapati wrote:

i did check the apple support battery check, it said 88% yesterday before i updated to ios 18.4 after updating now it says 87% , the health is normal but the capacity is 87%.

And what are the charges for battery replacement if i have Apple Care?

iPhone Battery Replacement - Official Apple Support

That sounds super frustrating — a 2% battery health drop in just 10 cycles and under 10 days is definitely not normal, especially considering you’re using the 80% charge limiter, which is supposed to preserve battery health.

Here’s a detailed, realistic approach to help you handle this:

Let’s break it down:

What’s (Possibly) Happening:

• Battery health reporting is not always accurate in real time. After updates or certain usage patterns, the iPhone can recalibrate the battery health estimate. So sudden drops from 91% to 87% might be a result of recalibration rather than actual degradation.
• iOS 17.4+ (and especially 18.x) introduced battery health tracking changes that might show health more transparently — which can feel alarming, but isn’t always bad.
• Even though you’ve turned on the 80% charge limiter, high battery temperatures, background activity, or charging in warm environments can still degrade battery.

What You Can Do Now:

1. Check Battery Usage + Temps:

• Go to Settings > Battery – check if any app is consuming a lot of battery or causing heat.
• Avoid charging the phone when it feels even slightly warm.

2. Change How You Charge:

• Avoid wireless charging or fast charging for a while — these can heat the battery and accelerate wear.
• Try using a 5W or 10W charger occasionally instead of 20W+, just to reduce thermal stress.
• Charge in cool environments and remove case while charging (if it’s a thick or heat-trapping one).

3. Reset Battery Stats (Soft Recalibration):

Let your battery go below 10%, then charge all the way to 100% once or twice (disable 80% limiter just for this), while the phone is off or idle.

This won’t repair the battery, but it can help the system read the battery health more accurately.

4. Turn Off Optimized Charging for a Few Days:

Settings > Battery > Battery Health & Charging > Optimized Battery Charging — turn it off temporarily.

Sometimes this feature bugs out and keeps charging habits stuck in a weird loop, especially after updates.

Important: Keep an Eye on Cycle Count

• If you dropped 2% in 10 cycles, that’s about 0.2% per cycle, which is unusually high for an iPhone 15 Pro Max.
• After 11 months, you should be at ~89–91%, not lower. If it keeps dropping this fast, your battery could be defective.

Next Step if It Continues:

• If your iPhone is less than 1 year old and under AppleCare, Apple will replace the battery for free if they see the degradation as abnormal.
• Even out of warranty, Apple can run diagnostics and sometimes approve a battery replacement if health drops are abnormally fast — so don’t wait too long.

You can book a Genius Bar appointment or run a remote diagnostic via the Apple Support app.

Let me know if you want help running diagnostics or preparing what to say to Apple — happy to help with that too.

Batteries, being analog devices, aren’t as neat or linear or predictable as well-behaved digital devices. The only important factor is staying above 80%. If it goes below 80% have the battery replaced.

BTW, whether you use the 80% limit, optimized charging, or no battery management there is very little you can do to manage battery longevity, and about the only thing you can do to compromise longevity is to routinely let the battery drop to zero before charging it. You should charge when it reaches 20%.

The battery health % is just an indicator, not to take way too serious. Your battery life percentage can have been adjusted with the 18.4 update if you got that, or any other - or it's just a new "guesstimate" on your phone. Your battery will lose capacity no matter what you do - and the only good way to ever preserve a battery is to not let it drop below 20-25% and stop charging it when it hits 80-85%, but this is only on new batteries - which also dies sooner or later, unfortunately.

The battery in your iPhone 15 Pro Max was designed to go up to 1,000 Charge Cycles under ideal conditions before the battery reaches 80% Maximum Capacity

That works out to a 1% drop every 50 Charge Cycles.

How many Charge Cycles has your battery completed? Whatever that is, divide that number by 50 and that should work out to the current Maximum Capacity of your battery.

For example......your battery has completed 500 Charge Cycles. 500 divided by 50 = 10%. So, the current Maximum Capacity of your battery should be 100% minus 10% = 90%.

Totally get your concern—it makes sense, especially since you’ve been using a proper 25W charger from the start. If it were a charger issue, it likely would’ve shown earlier.

Ahmedabad’s heat can definitely affect battery health over time, especially combined with a super tight case that might be trapping heat. The timing of the battery drop right after switching cases could be more than a coincidence.

Switching back to your old case and charging fully for a few days sounds like a solid plan. If things don’t improve, checking with Apple is a good call. Keep me posted!

You could have Apple Support check the battery, but I do not think they will find anything wrong. Apple will not replace the battery unless the Maximum Capacity drops under 80% in the first 12 months.

The normal AppleCare warranty in most countries is 1 year.

A replacement battery in the U.S. costs about $100 (U.S.).

Even if you are willing to pay, Apple will not usually replace the battery unless the Maximum Capacity has dropped below 80%.