I installed a Harbor Freight solar panel on my Mighty Mule MM271 opener to save money as well as added a second cheaper remote control.

Solar Panel
https://www.harborfreight.com/7-watt-...

Ammo Box
https://www.harborfreight.com/030-cal...

Gate Opener
https://amzn.to/3HbfB9Z

Remote Control
https://amzn.to/3BVWi0a