For all my equipment requiring mercury cells, I have been using zinc/air cells. For the last 20 years or so. Here is a typical discharge curve:
Thanks for providing this interesting graph. I do wish the discharge curve from a mercury cell could be included for reference, but I guess that is no longer practical.
For those of use who are mostly ignorant of all things electrical, can you help us draw any practical conclusions from your data set?
I might be tempted to conclude some brands last longer than other brands, but I don't know how much variation there may be within a single brand. That is, if I bought the same brand of battery from many different sources over a period of several years, would they all produce about the same curve? Or do variations in manufacturing and/or storage conditions produce significanly different curves from a given battery? Does each line on your graph represent a single battery, or an average of results from several different batteries of the same brand?
I might be tempted to conclude that if my camera meter draws about 0.5mA, then my battery should be good for at least 225 hours. But I have no idea how much current my camera meter actually draws. And even if I did, my experience with batteries suggests there is a big difference between how long it takes to run a battery down all at once, compared to how long the battery lasts when used periodically.
I might be tempted to conclude that if a battery measures 1.2V or less, then it should definitely be replaced. But if I understand correctly, measuring battery voltage is a little tricky. Something about getting different results depending on whether or not the measuring circuit includes enough load???
I notice the batteries seem to sort as two different groups according to their starting voltages -- some closer to 1.40V and others closer to 1.48V. What I don't know is, how does the slightly higher voltage affect the meter reading? And on the other end, as the voltage drops, at what point does the meter reading become affected enough to matter -- which I think most people define as an error of about 1/2 stop?
Can you tell us anything about built-in battery testers such as the one on my Konica Autoreflex T4? At what voltage would the test light come on, or fail to light? If the the camera's built-in battery tester is reliable for mercury batteries, will it also be reliable for zinc-air and/or other battery chemistries? I assume the camera's built-in battery tester only indicates when the voltage is too low for accurate meter function -- and would not indicate a problem if the battery voltage is too high?
Finally, what is the significance of the 1.08V reference line?
Thank you, -gw