Absolutely right. At first i wanted to realise this project with a Adafruit Feather M0 circuit with an ATWINC1500 on top. Some months ago i've already used this for connecting a project of mine to my local 2.4 GHz wifi network and it worked very well. As Thomas Beck mentioned, LoRa has some advantages over Wifi especially range and frequency. Because of the metal housing of a car, i didn't want to cause any connection issues or other problems with communication range. Therefore the lower frequency should be better for this project.

> Very much effort for just reading the battery voltage! Well, this is true ;) However, an OBD2 scanner is not suited for this job. The reasons are: 1. needs a vehicle that supports OBD2 2. needs a control module in the vehicle that supports an OBD2 service 0x01, PID 0x42 request (control module voltage)    Furthermore, control module voltage measured by a control module might be significantly less than battery voltage due to protection diodes or other circuitry being in the power supply path. 3. needs at least ignition on, engine off state - at least all cars with whose I have tested my OBD2 Labs projects (e.g. OBD2 for Arduino) needed this. With ignition on, all control modules of a vehicle are awake, vehicle busses are running and the battery is drained very fast. Therefore, OBD2 plugs which are permanently connected have a manual power switch or special circuitry to detect vehicle wakeup. When a vehicle is in sleep mode, these plugs are completely switched off or are in low-power mode, too. Furthermore, with LoRa you can achieve significantly larger distances between transmitter and receiver compared to WiFi or Bluetooth. Additionally, LoRa needs not much energy since the transmission time for a small packet is very short. Of course this comes with a drawback, data rate is very low. Since only a single voltage value has to be transmitted every 100 seconds, data rate does not matter.

Very much effort for just reading the battery voltage! What about using an OBD2 scanner which will be connected via Wifi or Bluetooth to your smartphone. Or taking an OBD2 connector and put in a self programmed ESP8266. But anyway, the idea monitoring the battery voltage is good, espacially in the winter season.

Très pertinente réflexion de Kenneth mais celà augmente le coût de l'ensemble et l'utilisation de composants low power s'accompagne aussi d'une miniaturisation. Peut-être qu'un objectif moins ambitieux de 16 heures extensibles par générateur solaire selon les besoins permettrais de diminuer le poids global.

I'm going to start with the active development of the clock. I was hoping to have a Reneses development kit but it hasn't arrived yet, so I'll start creating the first prototype using Arduino and some external modules. I would like to have something functional in the next few weeks.