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| A variety of 9 V batteries. Image courtesy Lead holder, CC BY-SA 4.0 via Wikimedia Commons |
Nowadays,
if you go to a shop to buy batteries, apart from the coin cells, the
chances are you'll only have five types to choose from, if even that.
Those are the AA, AAA, C and D sizes and the small, square 9 Volt PP3
(Also designated as type MN104 or 'E'). In the 70s, there were a
multitude of battery types, now pretty much obsolete or hard to come by.
So in addition to the PP3, there were several different sized 9 V
batteries with different capacities, made for powering portable
transistor radios and other electronic appliances. A 6 V battery with
two spring terminals on top was available for powering lantern type
torches with handles, and a smaller 4.5 V battery (3LR12) with two, flat
springy brass terminals on top was available for slim, flat pocket
torches. The cylindrical, handlebar-mounted style of bicycle lamp we use
today hadn't been invented or at least wasn't common and Ever Ready
bicycle lanterns were more the norm. These were powered by a 3 V No.
800 battery, composed of two, 1.5 V cells in series, the two cells
arranged side by side, with springy brass terminals. Other types of
batteries included the U14 for gas lighters and Ever Ready 3V No. 8
batteries (not sure what these were for, possibly small torches).
What's the difference between a cell and a battery?
Cells
work on the principle of potential differences created between
dissimilar metals or other material (e.g. carbon) placed in an
electrolyte (a chemical solution, paste or gel). So for instance one
type of cell technology is the Leclanché cell. This is a wet cell (using
a liquid electrolyte) invented in the 19th century, The dry version of
the Leclanché cell is the zinc carbon "battery" which we used before
alkaline batteries became widely available in the late 70s and early 80s
under the Duracell and Energiser brands. Cells only produce around 4
volts maximum (for lithium ion) and 1.5 volts for alkaline or zinc
carbon. To get higher voltages, we connect cells in series in a chain,
so the voltages add up. We call the collection of cells a battery.
A car battery has six cells connected in series to give a nominal 12
volts. Each cell produces 2 volts nominally. (In reality a fully charged
car battery gives out over 13 volts).
This Wikipedia article lists all the current and obsolete battery types, giving details about their uses.
Image courtesy Lead holder, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons