Protecting a cut out relay

Discussion in 'Embedded Systems and Microcontrollers' started by offthegridshed, Jan 3, 2016.

  1. offthegridshed

    Thread Starter New Member

    Aug 24, 2015
    Hi Guys,

    I need to protect a solid state relay that I'm using as a cut out relay.
    The relay is activated by an Arduino and passes charging current to a battery bank. I just cooked a relay as I wasn't concentrating and forgot that without the generator running it would draw current and act as a motor..:(

    I'm looking for any suggestions/guidance on what diode (or alternative) would be suitable.
    It's working parameters are up to 36v dc and charging current of 20a (25 to be safe). Ideally the relay would never be switched unless there was a sufficient charge coming in and the motoring scenario wouldn't happen, but based on today's experience I think a bit of safety would be wise.

  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    More info on the generator would be better, can you not power the relay coil from the generator output or field winding?
  3. offthegridshed

    Thread Starter New Member

    Aug 24, 2015
    It's a vintage lighting plant, shunt and series wound. It needs to be disconnected from the batteries before it is shut down as the relay operates from a min of 3v. Therefore it'll motor before the relay disconnects and then cook the relay or latch the relay before sufficient current is produced for charging. Hence the arduino is going to control everything.