In another item (under the same URL) they show that
the amount of energy delivered by a D battery cell can be
81,000 J. This was calculated from the 15 ampere-hours
"ability", assuming a constant current.
Note that I am substituting "ability" for the inappropriate
term they use, "capacity." Is this better? Also note that
81,000 J will take 1 kg to an elevation of 5 miles!
Ludwik Kowalski