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-The [https://wiki.wemos.cc/products:lolin32:lolin32 Wemos LOLIN32 ] is a ESP32 based IoT development board.
+The [https://wiki.wemos.cc/products:lolin32:lolin32 Wemos LOLIN32 ] is a [http://espressif.com/sites/default/files/documentation/esp-wroom-32_datasheet_en.pdf ESP-WROOM-32] based IoT development board.
 It is available in the [https://hacker.parts].
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   i2c.scan()
-== Open Questions ==
+== Battery Monitoring ==
+Unfortunately, no direct method of battery voltage measurement is built into the system.
+But it should be quite easy to implement such a thing: Use a voltage divider on the battery to get a 1.1V max. For a 4.2V cell, this can be achieved using a 27k and 100k resistor.
+Note, that the ADC of the ESP32 is set to 1.1V range by default! You can use the attenuation but this is not available on every platform.
+  ^  V_bat
+  |
+  R1 = 100k
+  |
+  +----o ADC
+  |
+  R2 = 27k
+  |
+ GND
+Now you can measure the voltage on the battery using the ADC. As the ADC is 12bit, you can get the actual voltage by multiplying the reading by ((27+100)/27) * 1.1 / 2**12, or in more general terms: ((R1 + R2) * V_ref) / (R2 * 2**Resolution).
+Super nice would be charge monitoring. The TL4054 can do this, you need to hookup to the PRG pin. But this results in nasty bodges on the SOT23 chip...
+== Battery ==
+The battery can be connected via a JST PH2 connector.
+They can be bought also from Conrad: [https://www.conrad.at/de/buchsengehaeuse-kabel-phr-polzahl-gesamt-2-jst-phr-2-rastermass-2-mm-1-st-740547.html ArtNr. 740547].
-* Can you monitor the battery voltage? Schematic says no...
 == Example Projects ==
 * Temperature and Humidity measurement using collectd as datalogger: [https://github.com/reox/esp32_sht21_collectd ESP32_SHT21_collectd]
+== Further Readings ==
+* [http://esp32.net/ esp32.net]
+[[Kategorie:English]]
+[[Kategorie:Interessensgebiete]]