My iPhone 15 Pro Max battery health dropping quickly after iOS 18.4 update

Makes sense why everyone that posts here is complaining about the decline in battery health. But when you say that the battery health can increase, do you mean that the percentage will go up, or it will just take longer to go down?

Chemical aging of lithium ion batteries is not linear (straight line). This results in curves that may have dips.

My wife’s iPhone 15 Pro Max is at 86% battery health. So, depending on the age of your battery, you could be doing really well.

Updates cannot cause decline to battery health. The only thing that causes decline to battery health are full charge cycles. With factors such as usage, conditions, etc which can affect that. But not an update.

Decline to battery health is not linear, meaning you can lose a few more or less percent at one time. Time is also not a good measure of battery health as someone that uses the iPhone more often will see the health run down faster. So how many charge cycles do you have? That is an accurate and good measure to determine battery health decline.

Jeff Donald wrote:

“Updates cannot cause decline to battery health.” That’s pretty absolute statement. I’d rethink that sentence, but that’s just me. 😀

How about.. "Updates are not known to cause decline to battery health, but it may re calibrate it in which you can see a decline." 😀

It cuts both ways. When an algorithm is updated/revised, some users will see increases and others will see decreases.

But think about it. Who goes on a forum, social media platform and complains about increased battery health? What do they say, my battery health went up? How do I get my battery health to go back down?

The condition of the battery is the condition. You can’t really demonstrably change the actual physical condition. But algorithms can change their predictions of future performance. Hence to the reasons to modify predictions of future performance.

joshitha2572 wrote:

Battery health was 96% when the cycle count was 251.

Now my cycle count is 267 and battery health is 93%. And there is no difference in my iPhone usage over the past few weeks.

Hello!

That is slightly above normal decline. But it may stay like that for a while now. Don’t worry about it unless you notice a steeper decrease. Rule of thumb is 1% decline for every 50 charge cycles.

joshitha2572 wrote:

Battery health was 96% when the cycle count was 251.

Now my cycle count is 267 and battery health is 93%. And there is no difference in my iPhone usage over the past few weeks.

Your iPhone is expected to drop 1% per 50 charge cycles. So after 251/50 = 5.02. Apple rounds down any tenth of a percent so 6, which brings your battery health down to 94%~, about along the lines of your battery health. While it may seem like the sudden decline is detrimental, before that your battery was doing better than average, and is now still average. It is not underperforming. All back to the non-linear decline of battery health, you will see sudden drops and holds.

“Updates cannot cause decline to battery health.” That’s pretty absolute statement. I’d rethink that sentence, but that’s just me. 😀