iPhone 13 battery health dropping quickly

Who did you purchase the iPhone from? If it was a used iPhone, the battery would not have been at 100% after years of use. If refurbished, it’s possible you did not receive an Apple brand battery and the less expensive third party battery is providing sub-standard performance. Where did you get your iPhone?

Batteries, like people are individuals. No two people age exactly the same and batteries don’t age the same either. The exact usage, chemical makeup, storage conditions, exposure to heat and cold and about a dozen other factors mean that every battery ages differently. Battery aging is not a linear (straight line) and degrades at different rates as the chemicals in the battery age and other factors mentioned above. The graph below shows the 4 batteries that were recharged differently and look how differently the batteries capacity changed with age. There is nothing linear in the aging process.

Apple expects your battery health to be at 80% after 24 months. If your battery health misses that expectation, contact Apple Support.

Please review the Apple Support articles on battery optimization. It contains the best  current practices for battery charging.

iPhone Battery and Performance - Apple Support

Batteries - Maximizing Performance - Apple

About the battery and performance of iPhone 11 and later - Apple Support

there is no such thing as overcharge with modern batteries

no matter what you do the health will go down you can only delay it's decay and replace it when the time comes.

have you read About

the battery and performance of iPhone 11 and later - Apple Support

and maybe

iPhone

Battery and Performance - Apple Support

and Batteries

- Maximizing Performance - Apple

Your iPhone battery health is expected to drop at about 1% for every month, and the decline isn’t always linear. Meaning some months you can lose more percent, other months none at all.

After 7 months of your iPhone, you should be at around 93% battery health, instead you are at 95%. So your battery is ahead. Even though your battery health declined 4% in a month, it didn’t drop any percent the many months before that. Back to what I said about the non-linear decline.

Keep in mind, all rechargeable lithium batteries chemically degrade over time. When your battery health reaches 80%, have the battery replaced.

Your phone.....assuming that it was new when you purchased it......is about 6 months old. On average.....over longer periods of time, the battery will decline about 1% a month. But, that's an average. It is probably fair to say that all batteries behave differently.

If it were my phone, I would expect that the battery would be in the 94% range. Your battery is at 95%.

I don't understand why you are concerned about your battery. It is doing just fine.

My recommendation would be to set the battery up to use Optimized Battery Charging and connect the power supply to the phone every night and leave it connected all night......every night. The battery will charge relatively quickly to 80%, then very slowly trickle charge up to 100% by the time that you are ready to use the phone the next day.

If you are only charging the battery to 80%, you are going to have to charge your battery more often. There is no advantage to doing this. You can do this if you want, but you will spend a lot more time watching the battery when you don't need to do this.

You will drive yourself crazy if you are checking the battery all the time and worrying about its performance.