1. Two CR2s in a 6-volt camera
Many 35mm film cameras take two CR2 cells side by side. Both have to be the same type and roughly the same age, and both go in the right way round.
2. The 4LR44 in older cameras
Some older cameras and flash units take a single 6-volt 4LR44, which is four LR44 cells stacked in one case. The code is printed inside the battery door.
3. CR123A in digital cameras
Compact digital cameras and some LED torches take a CR123A. It is a 3-volt lithium cell that holds about 1500 mAh, so it lasts much longer than a coin cell in the same job.
4. Don’t mix types
A camera that takes two cells needs the same chemistry in both. A new alkaline beside an old lithium gives an uneven supply, which can make the exposure meter read low or throw an error.
5. Check the contacts
The spring contacts in a camera battery compartment are small and corrode easily. If a fresh battery doesn’t register, clean the contacts with a dry cloth or a pencil eraser before you blame the cell.