How to check that the RCDs for my E-car charging station are working fine?

It is quite simple: in the same way as you are checking RCDs in your home installation, you just need additionally and adaptor for your electric vehicle charger.

Why?

You need to test it through the vehicle connector or socket outlet and in order to get power activated you need to switch the charger to charging mode. When the charger is in charging mode and you have power activated and life on the vehicle connector you can then measure it with an RCD tester (for example MFT) which can test both AC and DC types of RCDs and test it.