This is mainly for non-rechargables (acctually it could apply to rechargable too). Is there a standard load voltage drop vs load that's used to indicate the internal battery resistance is to high for practical use ? Digital cameras tend to be very picky about power supply. I've taken digitial camera batteries deemed BAD by the camera and used them succesfully in other less picky electronics. ( I wouldn't suggest using them in a pace maker). This begs the question: Are we discarding nearly good batteries ? Maybe recycling usefull batteries or worse sending them to the land fill.
As a hearing aid engineer (and one of 8.5 million users) I'm particularly interested in zinc-air technology, specifically with humidity. One engineer I know calls it a fuel cell, but nstead of pumping in O2 it extracts it out of the air.
Useful for what to whome? That was the midevil period though so anything "strange" might have branded you a witch.. without Generators to charge batteries you couldn't do much - and we didn't have generators until 1873, but wow things cascaded quickly once we had power generation.
I am very interested in this subject and wish today's products would be made compatible with rechargable lithium cells running at 3.7v and normal alkalines at 1.5v so we could start having AAA, AA, 9V (3.7x3), etc pure lithium cells. I know it might be somewhat tricky, but it would be nice to get rid of heavy, single use, low power density alkaline land fille batteries for good. With the speed we replace electronics these day's it wouldn't take long.
Batteries may have existed 1000 or more year before Volta: see Wikipedia's History of the Battery. If this was the case, it's hard to see why such a useful technology disappeared for so long. Perhaps it was banned by religious forces claiming it was the work of the devil -- or a scientific threat to religion. More likely there was a huge patent dispute which completely halted the Progress of Science and useful Arts :-)