[Power] $30 resin panel in my hands from eBay

[Mike Lee]

On Thu, Jun 20, 2013 at 7:24 PM, Richard A. Smith <richard at laptop.org>wrote:

> On 06/20/2013 04:51 PM, Mike Lee wrote:
>
>
>  Here are some initial photos:
>>
>> http://www.flickr.com/photos/**curiouslee/sets/**72157634232528701/<http://www.flickr.com/photos/curiouslee/sets/72157634232528701/>
>>
>
> Probably won't matter for you for testing but the wire contact points and
> a short bit of the wire should be coated with something like hot glue or
> some other thick coating. If there isn't some sort of strain relief I
> expect those connections will fatigue and break with a moderate amount of
> use.
>
> Electrically there isn't a whole lot of concern but if you happen to set
> it down on some sort of surface thats conductive you may lose some power
> that way.  I can image wet mud in a coastal area might have enough salt or
> other ions it it to be conductive enough to steal power.
>
> I was planning to seal the wire contact points. And then for strain
relief, which does seem essential, I have a bunch of these combination
adhesive mount/cable ties:

http://www.panduit.com/wcs/Satellite?c=Page&childpagename=Panduit_Global%2FPG_Layout&cid=1345564328975&packedargs=classification_id%3D120%26locale%3Den_us&pagename=PG_Wrapper

I would leave some slack on the leads and pin down with one cable tie and
adhesive mount.


>      through you swap the panels so that each XO gets run from each panel.
>>
>> Never would have thought to do crossover.
>>
>
>      the XO into the lowest possible power mode that you can still log data
>>     from.
>>
>
>
>  Yes, olpc-panelpwr-log. It took a couple extra pokes in Google to find
>> that zip package on GitHub.
>>
>
> Github? eh?  I don't really know what you are talking about.  I've never
> put anything on GitHub (That I know of, perhaps theres a mirror?)
>
>  Sorry. I though you knew where things were located already.
>


Ooops. Mistyped.



>
> Upstream git repo is here:
>
> http://dev.laptop.org/git/**users/rsmith/olpc-pwrlogs/<http://dev.laptop.org/git/users/rsmith/olpc-pwrlogs/>



That was the link I found.



>
>
> Copies of the scripts are here:
>
> http://dev.laptop.org/~rsmith/**pwr_scripts/<http://dev.laptop.org/~rsmith/pwr_scripts/>
>
> Sometimes whats in my pub html dir isn't quite the latest but I try to
> keep know working versions there.
>
>
>
>      until they charge up or your sun dies.   A voltmeter on the panel
>>     output while connected would be nice too especially if you have one
>>     that can log readings.
>>
>> The meter I currently have is pretty basic. But I will have my intern
>> record some readings off the two solder points of the panel using some
>> alligator clip jumper wires.
>>
>
> Sounds good.  Logging every 5 minutes or so should give an approximate
> idea of whats going on.   2 readings you want to get that are important for
> XO-1 are Voc (thats open circuit, ie nothing connected) when the panel is
> both cold and after its heated up.  So I propose you keep the panel covered
> with a towel or something connect up your voltage measurement setup and get
> it all ready.  Then expose it to the sun and quickly take the reading.
>  That will be Voc cold.  If you are curious you can watch it. Voc should
> fall as the panel heats up.  The 2nd Voc you want is after its been in the
> sun for a while and is good and hot.
>
> The alignment to the sun and amount of haze in your atmosphere will make a
> difference in your readings so you really want to do to this multiple
> times.  Say at the beginning and end of each test cycle.
>
>
I have a piece of cardboard from a pad of easel paper that I can use.



>
>  We'll make it standard practice to place the panel face down before
>> plugging it in. Then flipping it over to start the test.
>>
>
> I think a better test is without doing that and see if your XO ever trips
> the overvoltages.  You can tell that pretty easy with the voltmeter
> connected.  You should see a large drop in voltage when the XO starts to
> draw power from the panel.  If you don't see that then the overvoltage
> protector kicked in.
>
> Its a test for a negative though so even if you never see it that doesn't
> mean it won't happen for others but if you do see it then you know it will
> be a problem for XO-1 users.
>
> Voc on solar panel is maximum when the panel is cold. So if you want to
> see how high it can go put it in the freezer and get it really cold then
> quickly put it in the sun.
>
> I never saw the OV problem on at first connection with the non-limited GP
> panels until I was testing in the bright sun on a cold day in winter (IIRC
> around 0 deg C).
>
> I've never seen the other end of OV problem because I don't think I've
> manged to test in strong enough sun.  Its was reported by several tropical
> users though.  Once the battery charging reached the constant voltage stage
> the power into the battery falls off pretty quickly.  Over 85% or so of the
> battery charge will have completed by that time but its bothersome to never
> see it reach full charge.


Heh. A solar panel in one of our company pantries would keep my colleagues
guessing.

Seeing OV would be a stretch for me too as I won't encounter cold anytime
soon or intense sun.


>
>
> --
> Richard A. Smith  <richard at laptop.org>
> One Laptop per Child
>
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