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From: ems@Apple.COM (Mike Smith)
Newsgroups: sci.energy,sci.electronics,sci.med
Subject: Re: Electric cars?  Start with wheelchairs.
Message-ID: <3705@internal.Apple.COM>
Date: 19 Aug 89 01:10:28 GMT
References: <3659@internal.Apple.COM> <1526@cbnewsl.ATT.COM> <3637@helios.ee.lbl.gov>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 77

In article <3637@helios.ee.lbl.gov> wbrown@beva.bev.lbl.gov (Bill Brown) writes:
>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.  This is the same principle as jumper cables.  Hooking a
>>dead car's battery to a live car's battery allows the live one's
>>battery (and alternator) to charge the dead one.  You could probably
>>rig up a connector to do this for your friend, and it sounds like
>>it would be much appreciated.
>>
>
>It probably shouldn't be hooked up direct: maybe one of the "splitter"
>boxes used on RV setups would be the way to go.  These gizzies are
>esentialy a couple of diodes which allow both batteries to be charged
>by the alternator without having the relatively well charged (starting)
>battery dump mucho current into the relatively discharged (lighting, etc)
>battery, on in this case the wheel-chair battery.
>
>No real "science" here - just looks like an application for existing
>stuff just waiting to happen.
>
>(all this assuming a 12-volt system on the wheelchair)

Ahh, and therin lies the rub ... Chairs have funny connectors from 
the batteries to the control harness.  They are decidedly NOT designed
to be plugged and unplugged by a person with limited arm mobility (just
the kind of person who needs an electric wheelchair). They do funny 
things to connect the two 12 volt batteries into one 24 volt source.

The person in question cannot REACH the dash.  There is a custom
control/steering panel that moves to her lap when the chair locks
down.  She cannot put force into a plug (push or pull) but can
push buttons and move a joystick.

The usual behaviour is to have one's 'attendant' unplug the batteries
and hook up the charger ... The desired behaviour is to roll into the
existing custom chair lockdown and have it automatically hook up a 
charging circuit.

It also isn't just a matter of getting a Sears Best charger and slinging
it under the chair ... The chair often gets WET in the rain.  Would YOU
want to sit on top of a wet metal chair with the typical wide open 
charger box (vent slits) dripping onto the batteries ? 

So one needs a Very Smart charger to figure out what voltage it is being
fed (12v, or 110, or?) and turn it into what is needed (12 v x 2 batteries
or 24 v and charge them in series?).  It should also be small, light
weight, relatively flat, not get very HOT in operation (efficient),
and MUST be WEATHERPROOF.  It also would need to be able to automatically
cut out the control feed during charging ( since controls must be 24 v,
not the 12v from 2 parallel batteries ) and it should default to returning
control and stopping charging if anything looks funny (i.e. if it thinks
it or something else is broken it should get out of the way and return 
control to the operator, like in a power outage from the charging supply).

Oh yes, and it must not overcharge the batteries at all. 

It isn't quite as easy as it looks at first glance...  My hardware
skills aren't quite good enough to design such a device, but I would
be willing to finance construction ... and my wheelchair using friend
has volunteered to try out the product.

Mike

-- 

E. Michael Smith  ems@apple.COM

'If you can dream it, you can do it'  Walt Disney

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