Our satellite will be using 4 lithium ion batteries. Your job is to figure out
(1) what metrics do batteries need to tested for?
(2) how can we do these tests?
You can look at Rapid Testing of Batteries and Battery Capacity Tester Board
First Question - Metrics That Batteries Need to be Tested For? The methods that will be needed to test lithium ion batteries depend on the uses cases. These use cases seem to be[1].
I will primarily assess the performance and durability. I am under the assumption safety is not a concern as we are purchasing these batteries commercially from the Rapid Testing of Batteries section. Furthermore, the manufacturer states all safety states on page 8 of the cell specifications [17].
Here is a list:
| Use Case | Metric | Information and Importance | Source |
|---|---|---|---|
| Performance | Kilowatt hours | The amount of energy that a battery can deliver within an hour. The more kilowatt hours, the more energy storage and delivery. | [2][3] |
| Performance | Power & Energy density | The amount of energy a battery has compared to its size (per unit volume). Depending on the size of the satellite or holder, you want as much energy as possible. The higher the density of energy, the more energy you can pack in smaller units. |
Power density on the other hand is the amount of energy you can release compared to its size (per unit volume).
Batteries are usually made with a specialty with one of these characteristics, but cannot handle both [11]. | [3][6][11][12] | | Performance | Charge rate | The amount of time it takes for a battery to charge from 0% to 100%. If a battery's charge rate is 1C, it takes 1 hour to charge it from 0% to 100%.
Good image in [7] explains this nicely. | [3][7] | | Performance/Durability | Cycle life | This has more to do with longevity. The cycle life of a battery directly tells us the amount of full charges a battery can achieve before it loses its performance, or its capacity decreases to 80% of its initial capacity. | [3][4][5] | | Performance/Durability | Calendar life | The amount of time in which a battery can be inactive before its initial capacity decreases to 80% of its initial capacity. | [3][8] | | Performance | Swell rate | The amount by which the anode material (i.e. graphite) expands when charged. For example, if you charge your phone too many times the back compartment of your phone will fall off due to a swollen battery. | [3] | | Performance | Impedance | As taught in various of our electrical engineering classes, impedance at a simplified level is merely the total internal resistance against an alternating current. Too much internal resistance could lead to a lower lifespan and performance. | [3][9] | | Durability | Temperature | An increase in heat can have a negative impact on its lifespan.<br>"According to the 2010 BCI Failure Mode Study, starter batteries have become more heat-resistant. In the 2000 study, a rise in temperature of 7°C (12°F) affected battery life by roughly one year; in 2010 the heat tolerance has been widened to 12°C (22°F)." [13] | [10][13] | | Durability | Solid electrolyte interphase layer formation and growth | Every time you charge a battery, some of the electrolyte within the battery decomposes forming a thin layer called the solid electrolyte interphase (SEI). A healthy amount of SEI is good, but too much will cause battery degradation. Which is why charging too many times is harmful. | [14][15] | | Durability | Mechanical degradation | Batteries can mechanically degrade over time do to use. | [10][16] |
Second Question - Tests That Can Be Used?