Differences

This shows you the differences between two versions of the page.

--- eeng:topics:batteries:start [2024/09/29 15:44] – rolf
+++ eeng:topics:batteries:start [2024/09/29 16:05] (current) – [Capacity] rolf
@@ Line 1: / Line 1: @@
 ====== Batteries ======
-  * [[https://www.pveducation.org/pvcdrom/battery-characteristics/battery-capacity|Adafruit on Batteries]]
+  * [[https://learn.adafruit.com/all-about-batteries/power-capacity-and-power-capability|Adafruit on Batteries]]
-  * [[https://learn.adafruit.com/all-about-batteries/power-capacity-and-power-capability|PV Education on Batteries]]
+  * [[https://www.pveducation.org/pvcdrom/battery-characteristics/battery-capacity|PV Education on Batteries]]
@@ Line 8: / Line 8: @@
   * [[https://biz.maxell.com/en/primary_batteries/cr_heat-resisting.html|CR type cells, heat resisting, Maxwell]]
-The battery capacity $C$ is often given in $\mathrm{Ah}$ or $\mathrm{mAh}$.
+==== 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 = 1000\mathrm{mAh} = 1\mathrm{Ah} = 3600\,\mathrm{As}  = 3600\,\mathrm{C} $
+  * $C = 2000\,\mathrm{mAh} = 2\mathrm{Ah} = 2\cdot 3600\,\mathrm{As}  = 7200\,\mathrm{C} $
-  * Nominally: Continuous current of 1A for 1h. But: High discharge currents often lead to a reduced capacity!
+  * 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!
-  * Better: 10mA for 100h.
+  * Discharge at lower current: $10\,\mathrm{mA}$ for $200\,\mathrm{h}$. The product must be constant.