how many battery life my magic keyboard 2 has

Try to use apple diagnostics to see if it detects a problem with the keyboard or bluetooth or something. Instructions are below:

Brug Apple-diagnosticering til at teste din Mac - Apple-support (DK)

Click the link inside the link about reference codes. They will say what the reference code(s) you get means. I suggest you print the article or page, and keep it near you. It will be helpful when you do the diagnostics, so you can look for the reference code you got, and read what it means.

There is an app that I found compatible with Sierra, and it's name is ToothFairy. The bad thing is it costs like 6 dollars. It shows the battery of bluetooth devices. The link to the app store for the app is below.

https://apps.apple.com/us/app/toothfairy/id1191449274?mt=12

I don't know if what I'm saying is available on high sierra, so please tell me if you don't see an option. Go the system preferences, then keyboard. Look at the bottom left corner, and see something called "Keyboard battery level:". Do you see a percentage bar to the right of "Keyboard battery level:"?

Seems like if it doesn't have any charge or energy left(The grey stuff is what I mean. The grey stuff tell how much energy it has left. Like the magic mouse 2. It seems to look like if it has more than 50% of charge). Try charging the magic keyboard, and see if the grey stuff appears in the magic keyboard. Let me know if the magic keyboard's battery icon looks different or not.

Hold on. Let me try to understand this question that you posted(I should have asked you these questions in the first place. Sorry about that. 🤦)

ArazPoury wrote:

hi i have a magic keyboard 2 and is only work with big sur but it works on mac os sierra

So you are saying that the magic keyboard 2 works on sierra even though you said it only works with Big Sur?

ArazPoury wrote:

and the magic keyboard and i cant see the battery life how can i see it?

You can't see the battery life of the magic keyboard, or the magic keyboard 2? Do you mean both?

If the keyboard works on Sierra, but it is meant for Big Sur 11.3 or later...it is not fully compatible with Sierra. They simply didn't make the keyboard for Sierra. They made it for the newer macOS. That is probably why you can't see the percentage of the keyboard. What you need is a keyboard that is fully compatible with, and made for Sierra.

I do not know. You are simply using a modern keyboard on an old macOS. You need a keyboard that supports Sierra. They put the system requirements there for the keyboard for a reason. It is like running OSX El Capitan on a M1 iMac. It can't run it, because it's too modern for the OS. Also, it can't run any macOS that is older than the macOS it came with.

Click on the apple icon at the upper left corner, and click "About This Mac". Click on "System Report", and go to "Bluetooth". Look for the Magic Keyboard there under "Devices (Paired, Configured, etc.):". Under Magic keyboard, look for "Battery level:". It should tell you what the battery level is.

Weird. Are you sure you checked everywhere under Magic Keyboard that mentions battery level? If you are sure, then maybe it doesn't detect a battery from the keyboard or any percentage of charge from it?

Seems quite obvious that the keyboard doesn't support your MacBook, that it doesn't even detect a battery from it. The evidence keeps adding up. There is an app in the app store that supposedly detects the battery life of apple devices. The down side to it is, that it costs money. It costs like 2 dollars. Not only that, it doesn't support Sierra.