Why did so many early / cheap calculators use 9V batteries?

[Dieter]

(03-29-2018 05:32 PM)KF6GPE Wrote:  Getting to 5V with AA's or other batteries would require four, which is more bulk.

(03-29-2018 06:23 PM)Maximilian Hohmann Wrote:  my guess would be that it is just for small size and low weight that manufacturers chose 9V batteries. Also I remember that in the 1970ies 9V batteries used to be cheaper then the alternative of 3 to 5 AA (alkaline) cells.

All this is true if you compare a 9V battery with four AAs. But it's not if you look at AAA cells. Four of these have quite exactly the same volume as one 9V, and they can be arranged in different ways: 2x3 or 1x4, or even 3+1 (remember the battery holders for some 1980's cameras?). AAAs even offer more energy.

Dieter