I recharge my Volvo from a 13amp socket. The instructions that came with my Volvo T6 Recharge state that you should turn on the mains power before plugging into the car.. I want to charge at night at night to get the cheaper rate. I can understand that a cheap timer would not stand up to regular 10amp switching so had planned to install a heavy duty relay to do the switching. Is there any reason why this would not work or must the mains power be switched on before plugging into car.