I dropped a AA battery this morning, which conveniently rolled right under the fridge. Using a flashlight, I was able to see that it was about 12 inches (~30cm) back.
I tried reaching for it with a ruler, but that only pushed it back further. (Now it is about 18 inches (~45cm) back). Obviously I can't reach it with my bare hands, either. I'd very much like to not have to move the fridge, as it is rather full at the moment.
What household item(s) can I use to retrieve the battery?
If it's not too far back, a wire clothes hanger can be used. Locate the battery with a flashlight. Hold one end of the wire hanger, and push the other end of the hanger to the top of the fridge underside, until it has gone past the battery. Then let it down to the floor, and slowly draw it out. It will pull the battery with it.
Wire hangers work better for me because my fridge is low, so I'm less likely to push the item farther back with the hanger. If your fridge is high enough, I suppose a plastic one would work well because it would be less easy for the battery to slip out.
A tape measure can be used (reusable)
If you have access to the side, you can use a yard stick or broom handle to sweep the contents under the fridge forward.
If you have easy access to the front with a couple of inches (3 to 5 cm) clearance on the side, you can still sweep the item (this time to the side of the fridge) and use the yard stick to slide out the item from the side.
One of the nice things about this technique is that locating the object is not usually required.
Substitute other sticks as necessary.
There is a commercially available telescopic magnet that works well for getting small metal parts dropped into car engines that should solve your problem.
If you have an old radio antenna and a refrigerator magnet you could make your own.
