The original intent of this project was, that modern vehicles have increasingly sophisticated charging electronics that may not keep a battery 100% charged.
Thanks to the modern start-stop mechanisms and emission regulations, it is no secret that some of the batteries are only charged in overrun / propulsion operation.
In addition, the cold season also bothers batteries, which can cause sudden failures or deep discharges.
In order to get a constant state of charge of the car battery, a power-saving solution should be developed, which receives a short voltage measurement at certain intervals.
Further this value should be displayed on an power saving e-paper module, and stored for a longer graphical evaluation.
In order not to complicate the project, it was my goal to use as far as possible finished breakouts, and thus to keep the external wiring and layout creation as low as possible.
For example, the Arduino platform offered various breakouts with wireless radio standards, that allow strong radio signals without a lot of work.
Further, when used in a car, a suitable protective circuit of the hardware is necessary in order to remove interfering signals from the vehicle electrical system on the one hand and to protect the electronics used on the other hand.
For the reasons mentioned, a transmitter and a receiver were developed.
After hardware development and assembly, the development of an Arduino monitor software followed, in order to be able to serial control and debug both devices.
The logging function on an microSD card is also in function.
A continuously extended CSV file can be opened directly in Excel and can be evaluated graphically with just a few clicks.
The result ist very power saving for the car.
The current consumption of the transmitter is about 1mA in Idle mode, and 40mA for a very short transmitting process (about 1 second) every 100s.
The receiver needs about 40mA.
All functions are already fully realized, and work very well.