[Hennie Beukes]

I recently upgrade my Lumia 640 to windows 10 but it reduced my battery life dramatically. How do I revert back to the win 8 that it was pre-loaded with?

[xandros9]

I would recommend keeping Windows 10 and just erasing the phone first to see if it'll fix the battery life issue.

If you still want to go back, use the Windows Device Recovery Tool on a PC.

[Chintan Gohel]

I recently upgrade my Lumia 640 to windows 10 but it reduced my battery life dramatically. How do I revert back to the win 8 that it was pre-loaded with?

before going back, I would suggest holding out a bit until next week when a new update comes out. If that one also has a lot of issues, then you can do what xandros suggested