Heavy Duty Batteries
Why do they even call heavy duty batteries heavy duty? There is nothing heavy duty about them. I think the battery makers give it this name to scam people out of their money. I am one of those people. Finally I realized that alkaline is the way to go. So buyer beware and stay away from heavy duty batteries.
Heavy Dury (or 'for indistrial use') batteries are the low end of batteries - usually only good if you're short of cash & need new flashlight batteries.
As time goes on I find that more and more to be an old term. You now see them rate batteries more and more by the number of years they are warrantied, for example 4,5,6 even 7 years...
It's what we call a "legacy" term.
In the old days, you had several grades of batteries. Taking a look at the Eveready/Energizer line as an example:
At the lowest end, there was the regular carbon-zinc flashlight battery (the old Eveready "silver label" with the cat jumping through the number 9). Then you had the "Heavy Duty" carbon-zinc battery (Eveready's "gold label"), which supposedly offered a little more life than the regular ones-- and as I recall, they did last a bit longer. At the highest end, you had Alkaline batteries (which, since the early 1980s, are called "Energizers").
Somewhere along the line, they dropped the lowest level of battery and "Heavy Duty" became the new lowest-level.
Duracell's analogous product line was similar, with their basic line sold under the Mallory brand, their old corporate name.