Wrong battery percentage on charging

Hi , i have a macbook pro and today while charging when it reached 81 percent it suddenly said 100 percent. And my macbook charger shoes green light . But when i remove the charger it shows 81 percent. And in the settings app it shows fully charged 81 percent. Why does this happen pls help.

A bit hit and miss, but this recent post may help you.

Calibrating the battery as described in that post will very likely help you.

If it is utterly unfeasible to remove the CMOS battery, you can probably skip that step and perform the full drain and full recharge process. Resetting the CMOS just helps ensure it.

So as i can understand, i will remove the CMOS battery use it untill mac dies then charge it ?

Remove, then replace the CMOS battery prior to draining the battery.

The full steps are:
Remove the CMOS battery
If you have the setting in BIOS /EFI settings > Config for Disable Built-in Battery , select it
Hold the power button off for a good solid 30 seconds to drain capacitors.
Replace CMOS battery and reset in BIOS

Then:
Turn the notebook computer on and Do Not Charge. Use as normal until it is nearing death and then switch over to frivolous work or throw on an uninteresting video and let the notebook fully die.
Charge the notebook overnight.
The following day, power on the notebook and remove from charger. Use as normal until the battery dies again, then charge overnight again.

I realize that this is lengthy but... What this will do is recalibrate the battery sensor.

I have a dought here . After removing the CMOS and draining the caps do we have to reinstall new battery and use it until battery died ?

There are Two Batteries that we are discussing, so that may be the cause of confusion.
The CMOS battery looks like a small silver disk, like a US quarter dollar coin.
This will be pulled, then the button held down to drain the caps, then that small battery put back in. You do not need to replace it with a new one... unless it's bad... You can test it with any voltmeter.

The battery you are running until drained is the actual Notebook Battery.

Ok so first i will remove CMOS battery and then main laptop battery . Then hold power button for around 40 seconds to drain capasitors then put CMOS and the main battery then use it until the laptop battery dies and then charger . because if i don't remove main battery i think there will be electric current the caps

You only need to remove the CMOS battery.

You can remove both if you want to...

Some newer notebooks don't let you remove it. (Figures...)

The main battery should not discharge any into the caps. IF it does, it is faulty.

Ok so i will remove the CMOS and drain and then use the laptop battery until 0

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I will do it soon

Yes, remove the CMOS, hold the power button for 30 seconds. Replace the CMOS battery and perform the BIOS setting if applicable.
Then drain the notebook battery completely, then leave it off while it charges completely.
I recommend doing this more than once in a row.

I recommend doing this more than once in a row .

U mean to remove drain and charge again and again for 2 or more times

No, sorry, I wasn't clear. It is a good thing you check for clarification on these steps.

I mean the Drain and Full Charge of the Notebook itself. The CMOS and BIOS Settings (If applicable) only would be done the First time. You also only need to drain the caps the first time, too.
After that, it is just Calibration - and that only requires fully draining and fully charging.

Ok got it thank u i will do it soon

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Just to be clear that if i don't remove the CMOS battery and just drain the whole batter and charge it full will it work . Or if i am wrong then how to fix it without removing CMOS

Most likely, it will. If removing the CMOS battery is out of the question, just try a Standard Calibration for now by fully draining, then fully charging the battery a few times.