If you’ve got a Vauxhall Remote Key like this one then to change the battery is fairly straight forward. Just remove from your keychain and then with some slim device (a screwdriver or blade) just prise the key open and remove the old battery. It should come out easy! and then put your new one in. Now I like to write the date on them so that next time I know how long it lasted. and then simply put the other half of the case back on. Clip together. and then refit to your keychain. and that’s it. Battery changed. Thanks, Bye!