I believe in the Medicinal purpose for this battery.
We use similar devices today, like the tens machine (spelling?) small electrical discharges used by pregnant women, and now used for the control of
many Neurological symptoms, I have one I was given by the hospital, after bypass surgery left me with nerves which misfire wildly across my chest,
this helps when it becomes really painful, usually gets bad when I wear heavy clothing, the pressure against the skin can be painful.
I could see it being used for the likes of back pain or a lot of other painful symptoms caused by a lot of illnesses.
If your not sure what I mean, the machine is like those body toning gizzmo's, small electric pulses stimulate the muscles and help tone them up,
taken to the extreme by some who want the body, but wont do the exercise.
Can be a little shocking at first (pardon pun) but once you get used to it it becomes almost pleasurable.
It would have to give out a constant stimulous though, by the looks of this battery.
However in reality, it was probably used to power up the Baghdad lightbulb, which we haven't found yet.