Pretty amazing that 4 d-cells = 1 12Ah 6V SLA. Unless my math is wrong, which it probably is.
No it's not! Alkaline batteries are indeed just freekin' amazing,
IF..... your amp draw is small. I haven't quite puzzled out whether the amp draw capability differences between AA'a and D's is significant, but unfortunately, it seems that most taping equipment draws more than what alkalines can optimally supply. So you never get the full AH numbers. Whereas you do with nickel, lithium, and lead. But their total numbers are lower for the volume and/or mass.
Where is the free lunch, that's what I want to know
Peace,
Sanaka