Each two-button and three-button/single-channel remote requires one CR2430 battery.
To see how to replace the battery in your remote(s), watch this short video:
You will need a screwdriver or similar tool to release the battery compartment.
Correct battery position Incorrect battery position
MULTI CHANNEL REMOTE
The multi-channel remote requires 2 AAA batteries. Slide the battery door off the remote to access the compartment.