[Power] [support-gang] 3 portable solar choices for XO-1? (and other XO laptops, if poss!)

[Nathan C. Riddle]

On Wed, Jan 15, 2014 at 8:30 AM, Richard Smith wrote:

> On 01/14/2014 12:03 AM, James Cameron wrote:
>
>> On Mon, Jan 13, 2014 at 11:17:31PM -0500, Adam Holt wrote:
>>> 1) Our community deployments are re-ordering from Richard Yu @ Gold
>>> Peak (GPI): “Portable Solar Module, Item #GPSP151400, 15V 14W solar
>
> 14W? That should be 15W.
>
>>> panel with 18V limiter” currently used for the expanding XO-1
>>> deployment in Lesotho [... 29°28′S ...] can anyone remind/clarify
>>> whether the above works across all XO laptops (XO-1, XO-1.5,
>>> XO-1.75, XO-4), or is the above unit only really for XO-1s?
>
> Any GP panel 10W,15W or even a 20W with the 18V limiter will work for 
> all generations of XO as long as its setup for "12V" operation.  In 
> solar speak 12V means a typical output of 14V with Voc up in to the 
> low 20's.  Which is why you need the limiter for XO-1.
>
>> I don't think I have one of these, so I can't say from experience.
>
> I believe thats correct.  I sent you all unregulated panels so you 
> could test.  I don't think I even have any of them either.  I have a 
> sample of the 15W panel but I'm not sure if it has the limiter in it.
>
>>> 2) We'd obviously like a suitcase-ready solar panel that works in as
>>> many planetary situations as possible, aware this is unrealistic.
>>> Still, Lesotho's high-altitude/cold/bright XO-1 deployment will test
>>> a couple of AuriaSolar.com's rigid panels in adverse conditions
>>> (cold/bright/high-altitude) in both Idaho/Lesotho in coming
>>> weeks/months, just in case these can actually work with XO-1s, so we
>>> all understand better.  Very inspiring they're putting their neck
>>> out for all of us, if others have advice/warnings!  That Auria Solar
>>> model being:
>>>
>>>     "15-watt-solar-panel for XO-1.5, 1.75 and XO-4"  "XO-1 with 
>>> minor
>>> constraints"
>
> Here's where I need to insert a link back to where I've discussed this 
> before but I don't feel like digging though the archives.  ON XO-1 
> there are 2 possible failure modes.
>
> The first typically happens when you first connect the panel and the 
> output voltage is above the point where the XO-1 overvoltage trips. 
> This one can typically be worked around by letting the panel warm up 
> or by flipping the panel over, connecting it to the XO and then turn 
> it over and expose it to the sun slowly.  The XO will load the panel 
> and the voltage will stay low.
>
> The 2nd failure doesn't have a work around.  The charging profile for 
> the battery is a curve that decreases.  In the latter stages of 
> charging the load will only be few watts.  If the battery only draws 3 
> watts yet the panel has enough sunlight the produce more than 3 watts 
> you will get a voltage increase up to the panels output voltage for 
> the current operating temp.  If that resulting voltage level exceeds 
> the overvoltage level then the XO-1 stops charging before the battery 
> is 100% full.  The actual point at which this happens is very 
> variable.
>
Does case 2 apply to the Auria 15W panel of SF 2012?  The output spec. 
is 16.29 volts at 0.944 amps with an open circuit of 19.52 volts.  That 
is, is there sufficent load (XO-1) to maintain the output spec . (in 
Lesotho -- worst case)?  This case 2 did not occur on XO-1's for 
brightest summer sun in Michigan (no noise either). ncr

> With a 15W (or higher) panel it much more likely to happen sooner than 
> it did with the 10W panel.  So in theory it could result with an XO-1 
> that was only 75% charged or maybe even 50%.
>
> The 15W aSi panels are also more prone to this because the temperature 
> de-rate for aSi is much lower than panels from monoSi or polySi.
>
> Its a big math game with a bunch of variables to know if you will hit 
> this.  But it I have reports from 3 different places that match this 
> scenario.  One of which I was able to verify with olpc-pwr-log.
>
>
>> You might also search for more recent modules.
>
> On this note I've found a reasonable source for cheap polySi and 
> monoSi panels that are on a metal backing. Very similar to the GP 
> panel.  They suffer the same problem though with XO-1 in that without 
> some sort of limiter they may trip the over-voltage.
>
> I'll follow up with a post on these panels.  Been meaning to do that 
> for a while anyway.
>
> -- 
> Richard A. Smith
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