Why is my iPhone battery health decreasing every two days despite proper charging?

In addition, some users tend to micro manage their charging by never letting it charge to 100%. Even with the 80% limit, the phone will still need to charge to 100% at times to calibrate the battery health reading. When it is prevented from charging to 100%, then the battery health reading will not be accurate and those users will see a higher battery health reading until it is able to calibrate and then they will see a larger drop to reflect the accurate level.

At 206 Charge Cycles, your battery should be at about 96%.

Apple does not display tenths of a percent in the battery numbers and they round down. So, if your battery was at 97.9%, this would be displayed as 97%.

Your battery might have been at 98% one day, then dropped only .1% to 97.9%. This looks like your battery dropped 1% from 98% to 97% when it only dropped .1%

It is normal for the Battery Health to decline about 1% for every 50 charge cycles.

If the battery has gone through 300 Charge Cycles, the Battery Health should be about 94%.

How many Charge Cycles on your iPhone?

Your friends have truly amazing batteries. They must have really been at 105-106% when new. Apple would still display this as 100%.

Tell your friends that they need to send flowers to Apple.

Battery health decline on your iPhone is not linear and on a monthly basis you can lose more or less percent each time. It’s very possible your battery health stayed steady for a while and is now dropping a few points suddenly as a result.

Your friend’s got lucky with an iPhone battery that exceeded the manufacturers standard. But, no two batteries age the same.