[Power] Fwd: solar panels to gaza - any pitfalls?

[Richard Smith]

2nd try.. Needs to be power at lists.laptop.org  not power at laptop.org

---------- Forwarded message ----------
From: Richard Smith <richard at laptop.org>
Date: Tue, Feb 23, 2010 at 12:58 PM
Subject: Re: solar panels to gaza - any pitfalls?
To: Barbara Barry <barbara at laptop.org>
Cc: robert <robert at laptop.org>, "Reuben K. Caron" <reuben at laptop.org>,
power at laptop.org


On Tue, Feb 23, 2010 at 11:37 AM, Barbara Barry <barbara at laptop.org> wrote:

> hi richard,
>
> wad suggested i email you on solar (i guess i just make it before your new
> power list).

List made.. You get to be the 1st post.  Not you are not subscribed so
any response will get moderated.  I'll approve it and add you to the
"accepted" list but you won't get list email by default.   Most of it
you probably don't care about.  But you are welcome to subscribe if
you like.

> 2100 solar panels are approved and about to be ordered for gaza.
> every child who gets an xo laptop in the next few months (our first
> distribution there) will get a solar panel, too.
>
> these are 1.0, g1g1 machines.
> any pitfalls with solar panels that we need to be aware of and trouble shoot
> before distribution?

We have reports from South Africa, Kenya, and a few individuals that
in heavy solar conditions the over voltage circuit of XO-1 can get
tripped [1].

But we also have a bunch of places where the panel is working fine.

I'm working with gold peak right now on a voltage limiter option but
its not ready yet.  The samples I tested did not function correctly.

Unfortunately, there's not any good way to know in advance if the
panels are going to have problems or not.  You have to take some to
the site and test.

If the the problem occurs then there's not much you can do with out
modifications to the XO-1 or some sort of additional circuitry in
line.  You are left with covering parts of the PV panel to reduce its
output.

[1] Right now over-voltage is the prime suspect although an EC
charging code bug can't be ruled out.  We have field reports of XO's
stopping mid charge. I have very little details other than "it dosen't
work" the commonality among all the reports is heavy sun.

What I have been able to reproduce here in Boston is the no-load
shutdown when the panel voltage is above 18V.  The symptom is that you
plug up the panel to the XO in bright sun and nothing happens.  The XO
is turning off the power before things get a chance to settle into
what would normally be a working charge.   In this case if you cover
the PV panel connect it to the XO and then slowly expose it to the sun
it works.

--
Richard A. Smith



-- 
Richard A. Smith