batteries

docs/Assignments/week_11_Networking/networking.md

@@ -273,6 +273,43 @@ They should be the same on each board you wanna communicate with. The only flaw
     }
     ```
 
+## Charging my new batteries
+This week I got my Li-Po batteries delivered.
+
+![alt text](image-9.jpg)
+These batteries are amazing when you need lots of power quickly. But that also makes a bit more dangerous because they can discharge extremely quick. I already have a bit of experience with single cell li-po batteries. But not with multiple cell ones. To charge these you need a special charger that charges every battery cell separately otherwise a cell may go above 4.2 volts and get permanently damaged. We had one 5S Li-Po in the fablab but I didn't trust it because it had a nominal voltage of 11 volts. These cells also need to be checked every so often if the voltage doesn't drop too low.
+
+![alt text](image-8.jpg)
+5s cell with a nominal voltage of 11 volts. According to [this guide](https://fpvfc.org/beginners-guide-to-lipo-batteries) a cell shouldn't go below 3.2 volts and any higher than 4.2 will significantly increase the risk of the battery bursting into flames. 
+
+3.2 * 5 cells = 15,6 volts
+the battery should be at a minimum of 15,6 volts to avoid damage to the cells. This battery was way under that (11 volts). So I ordered my own batteries because I didn't wanna work with a fire hazard.
+
+Whenever I charged them I made sure to always be within eye sight of the batteries in case something happened. This is also described in the safety manuals.
+
+![alt text](image-10.jpg)
+![alt text](image-11.jpg)
+
+We also had a balanced Li-Po charger in the fablab. It is the IMAX B6 LiPro balance charger.
+
+![alt text](image-12.jpg)
+
+My LiPo batteries used XT-60 connectors and these weren't in the box. So I made my own connector.
+
+![alt text](image-13.jpg)
+
+The LiPo charger has a input range of 11-18 volts so I supplied that using my own powersupply since there wasn't a charger in the box.
+![alt text](image-14.jpg)
+
+When I first started charging I selected the LiPo charge function but that was wrong because it stopped as one cell reached 4.20 volts instead of all cells reaching 4.2. Then I started clicking through the menu's and found the balance function and that did charge them correctly. I also needed to configure how fast it charged. A good rule of thumb is 1C to 0,5C so 1x the capacity in MaH or half the capacity in 0,5 MaH
+
+![alt text](image-15.jpg)
+
+Whenever you are charging and press the right status button you can see the individual cell voltages.
+
+![alt text](image-16.jpg)
+Here you see the battery I first charged normally without the balancing feature. Here you can see there are some big differences in the cells.
 
 ## Sources
 * https://randomnerdtutorials.com/esp32-esp-now-encrypted-messages/
+* https://fpvfc.org/beginners-guide-to-lipo-batteries