@NeverDie Thx for appreciating the work done. There will also be an open source part in the future. When and how extensive the open source part will be, remains to be seen. The release of certain information (block diagram, ..., in this post) is related to those open source parts. There are some OBD solutions, however most of them (in my experience) give back low frequency data put by the car manufacturer on the OBD-bus (CAN, ...). Therefore transients evolving directly from the battery could only be recorded if the manufacturer sends those data accordingly on the bus. Due to the small bandwidth(also because of other car data that have to be sent, ...), such battery data are sent more often once per second or less. Fast battery events (i.e. cranking events, ...) are therefore imperceptible. Unless the manufacturer processes the fast events and then sends them (once per second or less), which is very unlikely if the manufacturer does not market this feature itself. Third parties devices for high frequency sensing costs several hundreds dollars. In my experience, important battery states (especially the fast ones) are recorded by measuring and processing corresponding data directly on the battery. I agree with you about the limits related to the communication over Bluetooth. But i think Bluetooth 5.0 will improve a lot. However, WiFi will always remain an important option due to the high data throughput. The combination of both (BLE & WiFi), especially with regard to energy consumption, will gain in importance.

@tsunami My setup is max 50m radius and 433MHz standard power RFM69s so a small 1/4 wave whip works reliably even from a below ground pump chamber 10m away. Your 915MHz at 200m SHOULD work on 1/4 wave if obstacle free line of sight, but you could try a 2.4GHz Wifi router at one location and use a mobile at the other to test if you can see the router. I can see at least 3 neighbouring routers identified on my mobile from over 40m away through masonry, 10 on the laptop, so it's a simple enough test. If you can see the router on either, 915MHz should be rock solid with a simple whip and no need of directional antenna.