Welcome to Battery Science! My name is Ethan and I work as a battery engineer and often get questions about battery terminology, types, etc… so I decided to start writing about it. I believe most people learn by analogy most easily, so that’s how I’ll proceed. Oftentimes electricity is compared to water, since the analogies are easy and general consistent for most concepts. Don’t forget, however, that analogies break down and are oversimplified while first principles are much more reliable.
1. Charge - Charge is the basic unit of electricity and is measured in terms of coulombs, which is defined as the quantity of electricity carried by 1 amp for one second. This turns out to be (completely arbitrarily) 6.242×10^18 electrons’ worth of electricity. In the analogy to water, coulombs would be molecules of water. [1] [5]
2. Current - Current is often taught by professors and high school teachers as a sort of ‘electrical stream’. It has units of Amps (A) or milliAmps (mA) and could be described as the velocity (speed with direction) or volume flow of electrical charge, much like a stream or river. The higher the current, the faster the flow of electrons/charge. [5]
3. Capacity - Capacity is the amount of electrical charge a battery can hold. Measured in milliamp hours (mAh) or amp hours (Ah), capacity is akin to the water reservoir of electricity. [2]
4. Voltage - Voltage is one area where the electricity-water analogy is lackluster. The closest metaphor would likely be the concept of height, or rather of potential energy. Since voltage measures electrical potential (in volts, V) this analogy seems apt upon first glance, but upon closer examination we realize that increases in voltage do indeed increase the total energy of a system, but this energy cannot be transformed to make the electricity flow faster (higher current) whereas potential energy can be converted to make water flow faster. [5]
5. Cell - The cell is the physical manifestation of electrochemical storage. It is the basic unit of batteries and stores charges using charged particles (called ions). Cells are used to shuttle electricity back and forth between energy states (aka ‘charged’ and ‘discharged’) similar to how a system of reservoirs could pump water up and down to store and release energy. [3][4]
Extra Credit! I don’t like following rules, generally, especially not arbitrary rules that some bozo (me) put in place so here’s one more battery science term!
6. Battery - Finally! About time I explained this one. A battery is actually somewhat of an ambiguous term, since it can be many shapes, sizes, chemistries, etc. In general, a battery is an electrochemical storage device composed of one or more electrochemical cell. [4]
That’s all folks!
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Sources:
[1] https://en.wikipedia.org/wiki/Ampere
[2] https://en.wikipedia.org/wiki/Coulomb
[3] https://en.wikipedia.org/wiki/Electrochemical_cell
[4] Electrochemical Cell Design by Ralph E White accessed on April 4th, 2018 via UMN Library.
[5] Electricity by Sally M. Walker; Andy King accessed on April 4th, 2018 via UMN Library.
[6] images from Pexels.com