RE: Charger plug-in

["Chris Tromley" <chris_t@microtrac.com>]

Eric Chang wrote:

> >From: "Chris Tromley" <chris_t@microtrac.com>
> > Yeah, I guess point I was making (remember I'm electrically 
> challenged) is
> >that connecting/disconnecting under load, especially with a 
> charger that
> > pulls big amps, seems like a Bad Thing regardless of which 
> end goes first.  It
> > came to mind because I have an Avcon receptacle and the 
> contacts seem small.
> >
> >Is it really OK to just pull the plug when you're drawing 
> 30-40 amps?  Maybe
> > occasionally but not regularly??
> >
> >Chris
> 
> It is not a very good idea.  If you actually give it a try, 
> you will see
> a substantial arc when you break the flow of current.  The 
> best thing to
> do is to rely on soft shutoff, but most chargers will not do this
> automatically.  If you can shut down the charger, its control 
> circuitry
> will throttle back the current flow smoothly without breaking 
> any contacts.
> 
> Consider the Russco charger, for example.  Near the end of 
> the charge, the
> charger will throttle the current as it senses increasing voltage.  At
> this time, it is relative arc-free to pull the plug.  But, if one is 
> opportunity charging, or the charger is set incorrectly (too high a
> voltage for old batteries), the arc problem will be back.  Pulling the
> plug will erode it after several cycles.
> 
> Possible solutions are to pop the hood, and turn down the 
> current control
> on the charger before pulling the plug.  Another is to use a 
> sacrificial
> set of contacts.  For some odd reason, this seems to be more 
> attractive
> to the average EV owner.

Thanks, Eric.  That's the answer I was looking for.

Chris