There are provided an electric charging system, an electric vehicle and an electric charger. Upon charging a battery, power supply lines of an electric charger are connected to the power receiving lines of an electric vehicle 12. The power receiving lines have a relay. The electric charger has a voltage sensor that measures a voltage between the power supply lines. The electric charger has a voltage processing portion that applies filtering to the voltage. Upon charging when charging power is supplied from the electric controller, a filtering process with a stability-oriented first filter is applied to the voltage. Upon a relay failure diagnosis that performs a failure diagnosis of the relay based on a change in the voltage due to opening and closing of the relays, a filtering process with a second filter that has a higher responsiveness is applied to the voltage.