Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!rat!vlsisj!davidc
From: davidc@vlsisj.uucp (David Chapman)
Newsgroups: comp.sys.laptops
Subject: Re: Solar powered portables?
Message-ID: <1991May14.004622.3436@vlsisj.uucp>
Date: 14 May 91 00:46:22 GMT
References: <17913@venera.isi.edu>
Sender: usenet@vlsisj.uucp (Usenet News)
Reply-To: davidc@vlsisj.uucp (David Chapman)
Organization: Compass Design Automation   San Jose, California
Lines: 32


In article <17913@venera.isi.edu>, lpress@isi.edu (Laurence I. Press) writes:
|> Does anyone have any information or ideas on off-the-shelf or home-brew
|> solar power for portables?

Most solar systems are designed to charge 12V DC systems (e.g. car batteries).
Follow the current thread on 12V adapters and just plug a solar panel into
the input of the DC-DC converter.

Be aware that solar panel output varies wildly with the weather.  For example,
on a cloudy day power output may be only half that of a sunny day.  So you
will need to:

1) have a huge power margin on your solar panel, or
2) run the laptop from a 12V battery and recharge the battery from the solar
   panels, or
3) use the solar panels to recharge the internal battery and don't try to run
   the laptop directly from the solar panels.

If you try option 1), watch out for the 18-20V open-circuit/low-load voltage
output of the solar panels.  This may apply for option 3) as well; make sure
that the charger or DC-DC converter input is sturdy enough to take the higher
voltage momentarily.  Also, remember that solar panels are current-limited, 
so you buy capacity according to the current they supply, not the quoted 
wattage which is usually spec'd at 17V.

I'm doing just this, and I will be using options 2) and 3).

                David Chapman

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