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5914Re: Force Battery Pack Supposed to be Isolated from Chassis Ground?

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  • dnqfrommp
    Nov 2 10:49 PM

      I forgot to mention that when I took the measurements my controller was unplugged, all the fuses had been removed from the EV fusebox, the charger was unplugged, the service disconnect was unplugged, and the charger negative wire was unplugged.

      I also did notice some capacitive behavior when I checked across chassis ground and Battery pack main negative.

      Does that change your guys assessment?

      Thanks for the input,

      --- In solectria_ev@yahoogroups.com, Ken Olum <kdo@...> wrote:
      > Quin, you can check very easily if your controller is the problem by
      > unplugging it. You can also distinguish resistive and capacitative
      > leaks by disconnecting battery positive from everything else (if your
      > car is like my 1998, it's sufficient to disconnect the service
      > disconnect, the controller, and the charger output.) Then measure the
      > voltage between battery negative and the frame. If there is a
      > capacitor, it will slowly decline as the capacitor discharges.
      > Then short battery negative to the frame temporarily to discharge any
      > capacitors. Then measure the resistance between the frame and battery
      > negative. If there is a capacitor, the reading on your ohmmeter will
      > slowly go up as the current from the meter charges the capacitor. The
      > final value (if not infinity) is the magnitude of the resistive leak.
      > Of course you also need to test the equipment you unplugged for leaks
      > between the terminals that you disconnected and the frame.
      > You can isolate leaks by unplugging things. In my case, the problems
      > were the DC/DC converter (capacitative) and the air conditioner motor
      > (a resistive leak of several megaohms), and the controller. I fixed
      > my DC/DC by removing the filtering circuit connected to the frame.
      > See http://autos.groups.yahoo.com/group/solectria_ev/message/5538.
      > Perhaps this was unwise: see the subsequent discussion.
      > Nevertheless I'm inclined to disconnect my controller capacitors from
      > the frame as well. My personal opinion is that the high-voltage
      > system should be entirely isolated to decrease the chance of getting a
      > shock. People have different philosophies on this. Mine is that a
      > dangerous voltage requires 2 connection to hurt you, and so it's
      > safest to start with none. Connecting electrical components to the
      > case of a device seems to me essentially to be saying that you would
      > like the operator, who might be touching the case, to act as part of
      > the filtering system.
      > To be honest, I have a non-isolated charger (PFC20), so on the one
      > hand I'm not living up to my principles, but on the other hand I have
      > an even stronger reason not to have ground faults.
      > Ken
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