[ausev] Ive discovered my scooter is over unity!!!

[Aaron Richardson]

I am seeing the excess voltage under load while on the road at higher
speeds.  The voltage is normal under load when I just start from a dead
stop.  Also the voltage is normal while at high speed and let off of the
throttle (no load).

Aaron


On Sat, 2009-05-16 at 13:10 -0700, tomsmail at wtez.net wrote:
> I believe this is normal, and the low quality meter might be just excacerbating what's already there.  Aaron, I don't think you ever clarified if you meant that the pack voltage remains high after resting for several minutes with no load, or if you took a sample while on the road under load?
> 
> I see the same thing on my EV under load.  I use a good Fluke meter with logging and supposedly very good transient frequency response.  The controller has a very large capacitor and the pack leads are pretty long so the system is like a gigantic (RLC) oscillating network.  Current or Voltage (whichever one I happen to measure) bounce around and them damp after several seconds, whenever I sharply depress or release the accelerator pedal.  This occurs with or without regenerative braking turned on.  I can tweak the controller to make this go away - by limiting current or setting precharge circuit voltage thresholds to higher values.
> 
> For me, "several seconds" has been around 10 seconds.
> 
> Tom
> 
> p.s.  Al Gore uses the harbor freight meters to measure temperature ;-)
> 
> --- gkrysztopik at satx.rr.com wrote:
> 
> From: gary <gkrysztopik at satx.rr.com>
> To: AustinEV News Announcements and General Discussion <ausev at austinev.org>
> Subject: Re: [ausev] Ive discovered my scooter is over unity!!!
> Date: Sat, 16 May 2009 08:40:53 -0500
> 
> Yes, I found that my magic $2.99 Harbor Freight DVM can create a lot of 
> energy.  Sometimes my batteries go from 12.xx volts to 14.xx volts after 
> charging.  I think GM uses these meters to measure fuel economy.
> 
> Gary Krysztopik
> www.ZWheelz.com
> www.aceaa.org
> San Antonio, TX
> 
> 
> 
> Erik wrote:
> > Some voltmeters also read funny in the presence of high frequency 
> > noise.  An analog meter usually won't lie, but my harbor freight meter 
> > can give some creative responses.
> >
> > On Fri, May 15, 2009 at 7:36 PM, Matt <mba at hazmat.com 
> > <mailto:mba at hazmat.com>> wrote:
> >
> >     Most likely, the battery pack voltage is drooping under high
> >     current (high
> >     load), and the reference voltage for the battery meter is drooping as
> >     well.  The measurement is only as accurate as its reference. I would
> >     investigate how you are powering your voltage meter and where it
> >     gets its
> >     reference from.
> >
> >     Matt
> >
> >     On Fri, May 15, 2009 6:20 pm, Chris Robison wrote:
> >     > Some questions:
> >     >
> >     > What is the make and model of your scooter? At what points in
> >     the system
> >     > are you placing your probes or clips? Can you reproduce the
> >     behavior on
> >     > a stand (with the rear wheel raised)?
> >     >
> >     > I could imagine motor regeneration causing temporarily higher
> >     voltages,
> >     > but if your 64V pack is "sitting" at 110V after shutting down,
> >     I'd guess
> >     > you either have a measurement error or a battery pack that won't
> >     last
> >     > long.
> >     >
> >     >   --chris
> >     >
> >     >
> >     >
> >     >
> >     >
> >     > Aaron Richardson wrote:
> >     >> I put a volt meter on my pack to see how much its sagging under
> >     load.  I
> >     >> see the resting pack voltage is about 64V (5x12v SLA).  When I
> >     >> accelerate the pack sags down to about 55 or so and then climbs
> >     as the
> >     >> scooter increases speed.  On a freshly charged pack it got to
> >     110V!!
> >     >>
> >     >> I dont think Im inducing current into my sense wires because
> >     the voltage
> >     >> goes to 64V when I let off the accelerator and coast at high
> >     speed.  It
> >     >> seems this voltage it right.  If I shut the scooter off then
> >     this is
> >     >> where the pack sits.
> >     >>
> >     >> So, whats causing this voltage and can I trust the sag voltage
> >     when the
> >     >> scooter is moving very slowly?
> >     >>
> >     >> thanks,
> >     >> Aaron
> >     >>
> >     >>
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