Macbook Pro showing black battery icon with bolt even when not plugged in

Hi,

I have a Macbook Pro that is 3 years old (purchased new). I have recently noticed some issues with the battery icon not showing proper state.

The Battery status reports Normal.

When the system is running off battery and no adapter is plugged in the battery icon on screen will show black battery symbol with bolt icon.

When the Power Adapter is plugged in it takes over 1 minute for the symbol to change to the white battery with the bolt icon. The battery will charge to 100%.

Just wondering why when unplugged why I don't just see a black battery icon and no bolt?

Also wondering why does it take over a minute for the icon to switch to white battery with bolt when the power adapter is plugged in?

Is this a software bug or something else?