Battery level fluctuates between 80% and 100% while plugged to power.

pataniskers wrote:

Hello! Requesting some help regarding some weird battery behaviour.

Context: I always have my mac in clamshell mode plugged to power with two external monitors.

Some time after I started using it plugged, the battery stopped charging past 80% as expected. It's been plugged for around 6 months and I haven't had the need to unplug it in this time - everything works fine.

However, in the past week it's been acting weird where if I'm not using it, it charges to 100%, and if I'm using it, it ping pongs between 80 and 100 for no apparent reason?

I attached a screenshot of the battery level in the last 24h. I started using it today close to 12pm and it's been very inconsistent.

The model is a MBP M1 Max 16'' and battery is healthy at 94%. OS is Sonoma 14.5.

Thanks in advance!

https://discussions.apple.com/content/attachment/07558309-5edd-4511-b8a5-1fb93051b0fd

Yes this is how it works with Optimize

Battery Health Management—About BHM battery health management:

M1/M2/M3 SoC

About battery health management in Mac notebooks - Apple Support

Intel

About battery health management in Mac laptops - Apple Support

The rule of thumb—if you are near the mains leave it plugged in, if you need the portability then run on the battery only—this is how you help optimize your battery charging and extend the working life of your battery by reducing the cycle count.

Determine battery cycle count for Mac notebooks

Determine battery cycle count for Mac laptops - Apple Support

pataniskers wrote:

However, in the past week it's been acting weird where if I'm not using it, it charges to 100%, and if I'm using it, it ping pongs between 80 and 100 for no apparent reason?

I understand Optimize mode and know it's normal to cap it at 80%.

What I'm saying is that my battery was operating consistently at 80% due to Optimize, but since last week it's fluctuating between 80 and 100 several times per day, while being plugged and with no changes in my workflow, which makes no sense comparing to the common behaviour of always operating at 80%.

I have not run it on battery for several months, it has always been plugged in, so the sudden behaviour change is what I'm asking help for.

BHM is not static it is dynamic. So you battery is being exercised a bit, no harm.

I notice in —particular— after any upgrade ( ie macOS 14.5 5/13 ) can invoke some re-calibration.

I would not try and micro-manage the battery charging, forget about it, let the software work for you.

I see no issue.

the rule of thumb remains the same—

if you are near the mains leave it plugged in, if you need the portability then run on the battery only—this is how you help optimize your battery charging and extend the working life of your battery by reducing the cycle count.