I have been asked to come up with a solution to measure the voltage of a regular 12 Volt lead acid car battery (actually three batteries in parallel). I know that I have to use a simple voltage divider to break down the voltage for the analog input of the Arduino.
The problem I have is that those batteries power
four three massive DC motors (120A maximum peak combined) and I have absolutely no clue if they have any integrated circuitry to prevent likely voltage spikes. I guess they do but I really don't want to trust that (since they are some cheap-ass motors from China as far as I know).
A way of protecting the analog input was discussed in this thread, but I am really not sure if it will endure potentially huge voltage spikes.
Also, I would like to know how to choose the right components. For the voltage divider, bigger values might probably be better (something like 1MOhm and 200kOhm for a voltage range of 0 to 30 Volts). But how do I choose the right schottky diodes? I have plenty of BAT43 diodes at hand but I am really uncertain if they are the right choice. As for the capacitor, something small like 3.3µF or even smaller might be okay since I just want to avoid overly quick changes in my readings.
Maybe someone can help me out with a little bit of advice. Thanks!
P.S.: Yes, I should clarify the situation with those motors and I will. But until then I could really learn something by designing this thing with very high voltage peaks in mind.
Edit: I found out that it is a 24V MY1020 motor running at 12V. I've read that it can also be used for generating electricity so I guess it has nothing to prevent from spiking into the system. Meh. :(