Why do electrical regulations in many countries require a Type B RCD or a 6mA DC residual current detection for EV chargers and not for home batteries? Is this due to stricter design standards. Any other reason?

 

Why do electrical regulations in many countries require a Type B RCD or a 6mA DC residual current detection for EV chargers and not for home batteries? Is this due to stricter design standards. Any other reason?

Inside an EV, the onboard charger works like a big AC-DC converter, and if something goes wrong, it can leak smooth DC current. Even a small amount—around 6 mA—is enough to “blind” a Type-A RCD so it won’t trip when it should. That’s why Type-A RCDs alone aren’t safe for EV charging. To fix this, the standards require either a Type-B RCD, which can handle all types of fault currents, or a built-in 6 mA DC detector in the charger so you can still use a cheaper Type-A upstream. These rules come from IEC 61851, IEC 60364-7-722, and similar standards.

 

I understand that, even that home batteries are subject to a different IEC standard, but why the difference? A home battery also has an integrated AC/DC converter to charge its batteries. To me it seems that this can cause the exact same problem that you mentioned.

 

Inside an EV, the onboard charger works like a big AC-DC converter, and if something goes wrong, it can leak smooth DC current. Even a small amount—around 6 mA—is enough to “blind” a Type-A RCD so it won’t trip when it should. That’s why Type-A RCDs alone aren’t safe for EV charging. To fix this, the standards require either a Type-B RCD, which can handle all types of fault currents, or a built-in 6 mA DC detector in the charger so you can still use a cheaper Type-A upstream. These rules come from IEC 61851, IEC 60364-7-722, and similar standards.

INSIDE an RV, all decent quality battery charging systems ARE ISOLATED between the input AC power and the DC output.

IN ADDITION, the DC system in all of the RVs that I have seen in the US are 12 volts, which is not considered a shock hazard.
Given normal skin resistance, 12 volts DC is not likely to deliver a hazardous "shock" current.
Consider that the more informative name for that "RCD" device is a "Ground Fault Circuit Interrupter", where is the shock hazard from a 12 volt appliance??? Also, if 120 volt appliances are powered from an inverter, and neither side of the inverter output is tied to the local "ground", there is no shock voltage circuit available. If, however, external mains voltage is present inside an RV, then probably the mains system safety regulations would apply.