Greetings Reebosh,
You're walking through the right steps to update the firmware using a Mac. Since the update isn't starting, have you restarted your Mac? If not, disconnect the MagSafe Battery Pack from the Mac and click the Apple logo towards the top-left, followed by Restart in the menu. After the Mac has restarted, reconnect the MagSafe Battery Pack to see if the update completes. If the update doesn't complete, you'll want to make sure the Mac is running the latest macOS. The steps for updating macOS are listed below and can be found in the following article.
- Click the Apple logo towards the top-left, followed by System Preferences.
- Click Software Update.
- Then "Click Update Now or Upgrade Now."
Update macOS on Mac
If you're running the latest macOS or the update doesn't complete, try updating via the iPhone. Prior to reconnecting the MagSafe Battery Pack you'll want to restart the iPhone and update iOS. Those steps can be found in the following articles.
Restart your iPhone
Update your iPhone, iPad, or iPod touch
After reconnecting the MagSafe Battery Pack it can take up to a week for the update to complete. This information can be found in the "Attach and remove your MagSafe Battery Pack" section of the following article.
How to use your MagSafe Battery Pack
Let us know how that goes!