I am building a electric vehicle relay controller. Which controls the High voltage relays among other things. I have built an automotive power supply circuit with strong inspiration from this article: https://www.analog.com/en/analog-dialogue/articles/comprehensive-power-supply-system-designs-for-harsh-automotive-environments.html
(using both the filter circuit and power circuit)
I still have problems with voltage spikes from relays outside my PCB, the HV-relays and vacuum pump relay and many more. I am aware of the solution of putting diodes across relays. And that works as a specific solution. But I would like to install the control board in other cars as well without needing to put diodes across all relays in every car I do this on.
I have tried everything. As it says in the article I have used TVS diodes across the input voltage. And I thought that would solve it, but as soon as I remove the diodes(different diodes) over one of the many relays the problem appears again. If someone could point me in the right direction of what more I could try I would be very grateful.