Main difference betwean RCD type A and type B:
RCD A with DC detection:
This kind of combination detects AC currents at 30mA of fault current and DC currents at 6mA. The highest possible frequency to detect fault currents is 50Hz. It is a little bit cheaper option to use in charging stations.
This device detects AC and DC currents both at 30mA of fault current. The highest possible frequency to detect is 1kHz, much higher than other version. We recomend this kind of protection. Chargers in EV transform AC voltage to DC by using switching voltage regulators. This switchers can generate higher frequences which RCD A won't detect.