Xref: utzoo sci.energy:537 sci.electronics:7488 sci.med:11720
Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!stout!cook
From: cook@stout.ucar.edu (Forrest Cook)
Newsgroups: sci.energy,sci.electronics,sci.med
Subject: Re: Electric cars?  Start with wheelchairs.
Message-ID: <4038@ncar.ucar.edu>
Date: 21 Aug 89 20:11:52 GMT
References: <3659@internal.Apple.COM> <1526@cbnewsl.ATT.COM>
Sender: news@ncar.ucar.edu
Reply-To: cook@stout.UCAR.EDU (Forrest Cook)
Organization: Field Observing Facility, NCAR, Boulder, CO
Lines: 39

In article <1526@cbnewsl.ATT.COM> spf@cbnewsl.ATT.COM (Steve Frysinger of Blue Feather Farm) writes:
>From article <3659@internal.Apple.COM>, by ems@Apple.COM (Mike Smith):
>> A friend is in an electric wheelchair.  It is, in all
...
>> It cannot be recharged from her van.
>Of course it can!  All she needs is a connector (probably dashboard
>mounted).  The alternator and voltage regulator of the van will do the rest.

I have a friend who is wheelchair bound and has some similar problems.
His chair uses 2 12V deep cycle marine batteries in series for a 24Volt
supply.  He also has a customized van with no charger.
There are several ways that the batteries could be charged from the van:

1: The inefficient, easy way - use an inverter to convert the 12V from the
van up to 110 VAC and run the normal charger off of that.

2: The slightly less inefficient way - Make a custom inverter/dc supply that
can generate around 28 V from 12 V and charge the batteries with that.

3: The tricky but efficient way: - Build some switching arrangement on the
two 12V batteries so that they can both be charged in parallel directly
from the alternator.  Some kind of current limiting/schottky diode scheme
would probably be necessary to prevent killing the alternator or having
a charged battery dump too much juice into a dead battery.

Personally, I would try #2 first because it requires the least modification
to the chair.

My friend's wheelchair uses a very inefficient switching method to give him
speed adjustment.  The current is either run directly to the motor (fast)
or run through a giant nichrome resistor (slow).  I am currently checking
out some IRFZ40-ND Hexfets to see if they can hold up in a pulse-width
modulated switching circuit so that he can have continuously adjustable
speed.

 ^   ^  Forrest Cook - Beware of programmers who carry screwdrivers - LB
/|\ /|\ cook@stout.ucar.edu (The preceeding was all my OPINION)
/|\ /|\ {husc6|rutgers|ames|gatech}!ncar!stout!cook
/|\ /|\ {uunet|ucbvax|allegra|cbosgd}!nbires!ncar!stout!cook