Re: Solar Cells Won't Turn Motors

["Lawrence Rhodes" <bassoon@jps.net>]

Real Goods has a Solar car that works off the solar cell.  Lawrence Rhodes
----- Original Message ----- 
From: "David Dymaxion" <david_dymaxion@yahoo.com>
To: <ev@listproc.sjsu.edu>
Sent: Saturday, January 26, 2002 10:52 PM
Subject: Solar Cells Won't Turn Motors


> I'm helping my son do a science project for school. We decided to do
> a small toy electric car powered by a solar cell. I have seen little
> kits for this, but wanted to do it by scrounging for fun.
> 
> I've tried various solar panels and motors, but it boils down to
> this: I can't get the motors to turn at all, not even in free air! I
> feel I must be missing something fundamental but don't see what.
> 
> Anyway, the little PC fan motor is spec'd at 0.080 amps and 12 volts.
> Solar cell shows 12 Volts and 0.25 A on the multimeter, right on spec
> -- motor won't turn. Tried a little hotwheels motor (4.5 V) -- motor
> won't turn. Tried a small 1.5 V motor from Radio Shack -- motor won't
> turn. All the motors spin rapidly when a battery is applied.
> 
> A second solar cell was spec'd at 1.5 W, and the motor at < 1 W.
> Still doesn't turn. (By the way, this solar cell was just $10 at
> Harbor Freight, on sale today.)
> 
> I was thinking maybe voltage or current drops precipitously under
> load (Voltage was an open circuit measure, and current a closed
> circuit, low resistance measure). But it can't droop too bad, or
> these things would never meet their claim to charge car batteries.
> 
> Any recommendations would be appreciated! What do the little kits do
> that I am not doing? They certainly have smaller solar cells, but at
> least those cars presumably move!
> 
> 
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