The common battery voltage on aircraft is commonly referred to as "28 volts". What does that really mean in terms of a lead-acid battery?
In many uses, such as cars ("12V"), trucks ("24V") forklifts and golf carts ("36V" or "48V"), locomotives ("64V"), the nameplate number is exactly twice the number of lead-acid "cells". But in reality, the fully charged/charging/float voltage of the system with alternator running is higher - cars 14V, trucks 28V, locos 75V.
Battery units are generally sized at 3, 6 or sometimes 4 units (6, 12 or 8 volts nominal).
So, when aircraft power is specced at 28 volts -- do they actually mean a 14-cell lead-acid battery or two 7-cells (which is almost unheard of)... or do they actually mean a 12-cell battery with a "float" voltage around 28V, (built out of two common-as-dirt "12V to everyone else") batteries?
I hope this isn't overloading this question too much, but when nickel-cadmium packs are used, does that have 20 cells, or 19 or some other number?