If It's a Flamerite model F01 then the battery is contained within a removable section at the bottom end of the remote. Grip the two ridged blocks on either side of the bottom and pull the battery holder out. This may take a little fiddling it can be rather stiff and difficult to remove. Do not take the little screw out at the other end of the remote at the back it doesn't help.
Charles, November 2022
