Path: utzoo!attcan!uunet!bu.edu!wang!tegra!vail
From: vail@tegra.COM (Johnathan Vail)
Newsgroups: sci.electronics
Subject: Re: Electronic Car Brakes
Message-ID: <1414@atlas.tegra.COM>
Date: 24 Sep 90 16:29:29 GMT
References: <8581@ncar.ucar.edu>
Organization: Tegra-Varityper, Inc., Billerica, MA
Lines: 31
In-reply-to: cook@stout.atd.ucar.edu's message of 24 Sep 90 03:38:22 GMT

In article <8581@ncar.ucar.edu> cook@stout.atd.ucar.edu (Forrest Cook) writes:


   >[ lots of interesting stuff about electric cars and relative efficiencies ]
   .
   Instead of saying it can't be done and then whining when the Japanese do it :-) 
   ....
   How about electric car designs that brake by using the motor to charge back
   into the batteries?  Such a system could probably save several tens of percents
   in efficiency, especially for city drivers.  Are there any special tricks
   involved in doing this?  I can see how it would be possible to slow down
   by connecting higher voltage windings from the motor/generator to the battery,
   but is such a system able to come to a complete stop and use all of the
   braking for recharge?  Perhaps a PWM system would do most of that.

The problem is that the efficiency is low and the braking effect is
generally not good enough to get rid of "real" brakes.  I saw a
documentary about an Australian design that used braking on buses to
charge a hydraulic cylinder.  Then that energy was used to provide
acceleration.  This had the advantage of re-using some of the
otherwise lost energy of braking but the added acceleration allowed a
much smaller engine to be used, furthering the savings.  The system
was designed as a add-on that could be retrofitted to existing buses
at competitive prices.


"The death of God left the angels in a strange position."
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