Why is it that large batteries are nothing more than many small batteries connected? Why not just have 1 single, large battery?
In: Technology
Battery cells are made from 2 dissimilar metals that have a different “potential” with regards to their electrons. I know thats probably not the correct term. If you connect them via an electrolyte, which is usually an acid, you allow a chemical reaction to take place.
This chemical reaction redistributes ions from one metal to the other, with each metal being connected to a terminal. As a result, each metal has a different number of electrons and therefore a difference in charge. One will be the negative terminal because it has more electrons, and one will be the positive terminal because it has fewer electrons and more protons. The electrons want to get back to the other terminal to balance everything but they can’t undo the chemical reaction, so they need to have a conductive path, like your device, to get back.
The difference in the “potential” between the two metals is what determines the battery’s voltage, and typically there is not much difference between them. Zinc carbon batteries, for instance, one type of AA battery, only has 1.5V because the difference between Zinc and Carbon’s “potential” is 1.5V. If you want more voltage, you need to connect a bunch of these in series. If you want more current, you need to put some in parallel. And if you want more capacity, you need physically bigger cells. There simply is no way (currently) to make one big battery.
While the technology of Lithium Ion, which is all the rage right now for most rechargeable batteries, has a voltage of about 3.6V per cell, thats on the higher end of what a single cell can produce. And in fact, technically speaking, a battery is a collection of individual cells. Technically speaking, an AA battery is actually one cell in the AA form factor. A lead acid battery like you have in a car, is made of 6 lead acid cells at about 2V each.
Batteries can only put out a set voltage (usually 1.1, 1.2, 3, etc) per cell and that voltage isn’t very high. And batteries only have a certain capacity (usually rates in load vs time milliamp hours or something to that effect)
To get to the voltage you want you put cells in series, so their voltage is added.
To get a longer life of battery at the same voltage you put cells in parallel so they share load.
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