Mac battery: 80% but shows not charging!

Optimized battery charging may have paused the charging of your laptop. That's its job. Over time the algorithm learns your usage patterns and may pause charging until a time it estimates will benefit that pattern best.

Setting the 80% is to limit the full charge to 80%, not start the recharging when the level drops to 80%, which you posts seems to indicate is your expectation.

Here is some of Apple's guidance regarding battery performance, health and management:

Batteries - Maximizing Performance - Apple Support

About battery health management in Mac laptops - Apple Support 

About Optimized Battery Charging and Charge Limit on Mac - Apple Support

In a nutshell, to get the most from your battery:

• Let the OS and charging circuits manage the battery as designed.

• Plug in when using the computer near available power.

• Use on battery when ac is unavailable or when you must be mobile.

• Don’t subject the computer and battery to extreme temperatures.

• Don’t allow the battery to regularly discharge deeply before plugging in. Yes, it may happen from time to time, just don't make it a habit.

• Don’t obsess over battery life and/or health.  

❝Worry is the misuse of imagination.❞ – Zadra

I think this one sentence in the provided Support Article says it all.

• If the battery charge level drops more than 5% while connected to power, charging resumes, again charging to within a few percentage points of the limit.

About Optimized Battery Charging and Charge Limit on Mac - Apple Support

So, nothing wrong with the battery, it is working exactly as expected. I also agree with the others on the recommended charging methods.

algo_rhythm wrote:

Official Apple Support Community

What's up with my Mac's battery? I have an 80% Charge limit set up and the Optimised Battery Charging turned on.

78% is so close to 80%...

these are all approximations at best, I would not fret over this minor difference.

To be honest I would turn off all that user /feel good override options and let the macOS software work for you in managing the battery for best results.

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.

About Optimized Battery Charging and Charge Limit on Mac

About Optimized Battery Charging and Charge Limit on Mac - Apple Support

algo_rhythm wrote:

What's up with my Mac's battery? I have an 80% Charge limit set up and the Optimised Battery Charging turned on.

On my MacBook Pro with Optimized Battery Health active, I usually see it stay at 80% but sometimes it stays at 78% or 76% or even 74%. It is not always exactly 80%. This pattern is followed to maximize the battery life.