battery capacity lost

Remember Apple never exposed this information to the user before. The Full Charge Capacity (FCC) of Lithium batteries do fluctuate....some more than others. That percentage represents the FCC in relation to the original Design Capacity.

I monitor the FCC values when diagnosing Apple laptops to detect failing batteries when all the other standard information & diagnostics say the battery is good (the user is reporting issues though, so I'm trying to confirm the source of the problem...hardware or software). Even I cannot say for certain what is really normal here since I don't monitor those values in that way. All I know is that many people have posted about the quick drop in battery health over a short period of time just like you have mentioned...they've only been posting this on these forum since 2020 when the Apple Silicon Macs were first released and this information was exposed to the user by Apple for the first time.

Some of will depend on how the laptop is used. I would expect the more Charge Cycles that this health percentage will likely change more quickly as the battery chemical resources become more depleted (aka used). People who use the laptop on battery power a lot typically will need to replace their batteries within three years when the FCC drops below 80% of the original Design Capacity. Keep in mind Apple considers a battery has sufficient capacity as long as the FCC is at least 80% of the Design Capacity.

So if the drop rate of your battery remains consistent, then in 10 years your battery will be at about 80% of its Design Capacity. Most batteries will never last 10 years....most Lithium batteries will fail in about 5 years....so even a 2% drop in six months will still have your battery lasting 5 years. I find I replace most Lithium batteries after about 3 - 5 years.

Yes, you have always been able to use the laptop whether you are charging it or not. The battery may charge more slowly if the laptop is working extremely hard on something, but it will eventually charge when the workload lightens a bit.

Beginning with an update to macOS 10.15.x, Apple introduced a new Battery Management system to macOS for the USB-C model laptops where it will exercise the battery automatically when the charger is connected so you may see the battery charge level at 80% at times instead of 100%. This is meant to help keep the battery healthy. If anyone disables this feature, then if the laptop is connected to a charger all the time, then once in a while the laptop should be used on battery only to give the battery a bit of exercise.

About battery health management in Mac laptops - Apple Support

HWTech wrote:

Remember Apple never exposed this information to the user before. The Full Charge Capacity (FCC) of Lithium batteries do fluctuate....some more than others. That percentage represents the FCC in relation to the original Design Capacity.

It was available over 20 years ago when I got my first iBook. Not just with tools like coconutBattery but also directly displayed in what used to be System Profiler, although back then it was usually displayed as a mAh capacity and not a percentage (in 1% increments) as it does now in System Report. I remember when the old Apple Discussions had lots of conversations bragging about increasing battery capacity. I've saw it jump 13% once, but that was after an unplanned shutdown, and then when it went back up after the next full charge was complete.

That being said, this value fluctuates and can go up. I've personally seen that. Here's my log from coconutBattery.

naaskhansa wrote:

Is It OK To Use Macbook While Charging?

I usually leave my MacBook plugged in at all times and I'm concerned about whether using the laptop while it's charging will affect battery life.

Yes, it's fine. The only effect it will have on your battery life is that it will last longer as you're using it less.

Hi,

I think it's normal, tolerance the allowable margin of error.