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====== Batteries ======

  * [[https://learn.adafruit.com/all-about-batteries/power-capacity-and-power-capability|Adafruit on Batteries]]
  * [[https://www.pveducation.org/pvcdrom/battery-characteristics/battery-capacity|PV Education on Batteries]] 


  * {{https://biz.maxell.com/en/primary_batteries/CR2032HR_DataSheet_20e.pdf|CR2032 Cell from Maxwell}}
  * [[https://biz.maxell.com/en/primary_batteries/cr_heat-resisting.html|CR type cells, heat resisting, Maxwell]]

==== Capacity ====


The battery capacity $C$ is often given in $\mathrm{Ah}$ (Ampère hours) or $\mathrm{mAh}$ (milli-Ampère hours). 
\\ In fact, the unit $\mathrm{As} = \mathrm{C}$ (Coulomb) is the amount of available electrical charge in the battery.
\\ Example: If a battery of $C = 1\,\mathrm{Ah}$ is discharged with a current of $1\,\mathrm{A}$ then it takes 1 hour until it is discharged.


| {{https://cdn-learn.adafruit.com/assets/assets/000/004/149/original/components_graph_03.gif?600&direct}} |
| Discharging a coin cell with different constant resistors. Lower resistance = higher current. \\ Source: [[https://learn.adafruit.com/all-about-batteries/power-capacity-and-power-capability|Adafruit]] |

Examples:
  * $C = 2000\,\mathrm{mAh} = 2\mathrm{Ah} = 2\cdot 3600\,\mathrm{As}  = 7200\,\mathrm{C} $
  * Discharging: The Battery can provide a current of $2\,\mathrm{A}$ for $1\,\mathrm{h}$. But: High discharge currents often lead to a reduced capacity!
  * Discharge at lower current: $10\,\mathrm{mA}$ for $200\,\mathrm{h}$. The product must be constant.