XO Solar

Is 10 W the sweet spot under bright sun?

success, 11% to 48%

The current setup is two Harbor Freight 5 W panels, item 41144, rated at 350 mAh each. At $ 50 each, we're far from the $30 solar solution :-(

Sun May 20	finally got the battery to go up!	11% to 48% over about 2 h of sun	clear sky	Yamaplos 15:40, 21 May 2008 (EDT)</sub:>
Wed May 28	first full charge	@ 95 min, 42%, @ 130 min 56%, @ 174 min green light, 97%	partial cloudy to sunny	Yamaplos 12:17, 29 May 2008 (EDT)

Purpose/Scope

Test solar panel setups for the XO laptop

• What is the minimum panel that will work?

expectation is charging time of no more than 3 hours.

Tech Info - I just booted my XO-1 with a meter on the battery and for ~95sec, it draws 1A, after that it'll draw 1A with full backlight(BL). Setting to minimum BL shows ~850mA and with no BL shows ~800mA. Since it is a 6.7V battery, that's 6.7W(V*I=W) to pretty much run the XO with no power management and everything above that is free for battery charging.

The battery says 3.1Ah on it so for a fully discharged battery, you'd need another 1A or 6.7W above what the XO is using to charge the battery in 3 hours. Roughly. Basically, a 15W panel will do the job as specified(3h chrg) but a 10W will probably be acceptable in most cases. Doug LaRue 12:17, 06 June 2008 (PDT)

• Does size/output of panel affect charging time?

Yes. It's all about amperes, apparently. An engineer mentioned a $600+ flexible roll-up solution, currently available over-the-counter, meant for laptops on the go. Bless his heart.

• Controller

A controller downstream from the panel avoids battery overflow, and possibly also frying the XO. More research is needed before I will try a huge panel. Anyway, for now we should be safe, the panel I am using outputs only 120 mA, precisely one tenth of what the XO OEM charger brick gives. The XO battery apparently has such a filter, and there is also something called an Embedded Controller which controls battery charge and some power functions. I need do more work in this department.

Tech Info - yes, there is a built-in charge controller in the XO so there should be no need for an external charge controller. Only if you are connecting the panel directly to a battery pack will you need such an external charge controller.Doug LaRue 12:26, 06 June 2008 (PDT)

• What happens when a battery is slowly charged by a puny panel all day, which then boosts XO battery recharge?

I was given today a 1.2 Ah Pb Yuasa battery by Texas Solar Power Company owner Craig Overmiller to test that Yamaplos 15:00, 24 April 2008 (EDT)

such a small battery should be "safe", but otherwise I would have the same worry of shooting too many amps through. Tried it on, XO works. Now I will try to discharge it and then see what my panel can do. Simple theory is that it would take 10 hours to recharge (120 mAh, feeding a 1.2 Ah batt), that of course not counting any losses... Way too long. Need a larger panel for real life expectations. On the other hand, the XO runs just fine off the panel. Something is peculiar here. We'll see. Yamaplos 17:44, 24 April 2008 (EDT)

Figured out what is "peculiar". The XO is feeding from its battery even when hooked to the panel. Unexpected, and it might mess up things big time. Yamaplos 17:24, 27 April 2008 (EDT)

and so it was... :-( ~~ Yamaplos 19:58, 29 April 2008 (EDT)

Notes on Solar Panels and SLA batteries

• For maximum efficiency Solar panels need a 'peak power converter'.
• Charging SLA batteries above about 80% from solar panels cab be very wasteful (the charging rate drops off meaning you can't use all the energy available).
• Discharging SLA's below 30% (even 'deep cycle' ones) kills them. Quickly.
• SLA's therefore go from about 80% to 30%, roughly half the rated capacity.

Make available for sale XO Solar kits

The whole point of this is that this hardware be available for purchase over-the-counter, by anyone, very soon.

debate on the opinion issue and historical data
is in  discussion page. 

Many G1G1 donors would like to play around with alternative power sources like solar.

There seem to be a couple commercial efforts happening, Product News, Solar Panels

• ETA for XO Solar is May 2008

This is for the full-fledged, battery charging system. Still waiting to come across a larger panel, that probably I will have to pay out of pocket... hint, hint :-)

Expected cost of such hopefully will be under $75.

Transfer knowledge & experience

Use a Libre stance as to sharing what we find so that everyone can go solar if they can access the necessary hardware, without needing to purchase directly from us or our partners.

You can call yours the Jerry Solar Solution if your name is Jerry, and you can still call it that even if your name is Martha. I am getting my panels from Harbor Freight Tools, my plugs from Digikey, which we have not proved yet are the right ones, but we hope...

Facilitate XO Solar stuff for needy projects

Yes Nepal, we hear you...  :-)

This will depend, of course, on gathering funds to subsidize kits and shipping. A better accounted G1G1 has been proposed, in which developed world-purchasers would be able to purchase hardware in such a way that their purchase would make stuff available for needy projects.

Major Challenges

Amorphous Si panel

A 120 mAh, 12 V nominal panel (advertised as 1.5 W) is enough to "operate" (~6W is normally needed) the XO, but so far appears as not enough to charge the battery,. This is a Harbor Freight 44768 panel. Retails for about $13 plus shipping, similar price on eBay. Yamaplos 15:00, 24 April 2008 (EDT)

notice the exciting orange glow in the first "in the wild" solar XO, April 22 2008

XO

Since I was lent an XO that is solved for now. Applying for a developer XO so I can return this one. Wish me luck, it seems they're not giving them away that easy anymore.

Plug

The weird-beyond-all-understanding plug. Hope I can get some real ones soon for distribution of XO Solar, but it's a simple 20 minute hack for me to fashion one out of plastic straws and hot glue for testing.

got an email from Mike Lee a couple minutes ago with an offer for a sample of a real one. Great!

Yesterday purchased 10 CP-014-ND Digikey plugs, I have been told these are the right ones.

Caution! These are not the right plugs! I had got my information from the person in charge of power at OLPC, so take any information about this carefully, whatever origin it has. $18 bucks down the drain. Yamaplos 16:40, 27 April 2008 (EDT)

I bought some of those too. In the parts box they go. --Mike Lee 12:30, 4 June 2008 (EDT)

There is a current ticket about a better plug so hopefully this will no longer be a problem for Gen 2 XOs. Yamaplos 15:00, 24 April 2008 (EDT)

home made XO plug

Well, it took me more than 20 minutes, but it worked just fine. The central dielectric tube is from a BIC-type pen, the conductor surfaces from some thin copper sheet, the whole assembled with hot-temp glue. Caution do not use thermofusible plastics for anything electric unless you know exactly what you're doing. Same goes for any such XO hack. You're on your own! (don't that feel good, eh?)

Action

• get solar panels

I've been running a 1.5 W, 12 V nominal one since February 2007...

working setup now is two 5 W, 350 mAh panels Yamaplos

• get XO

got one for now. Borrowed from Austin XO

• get solar energy advice

Met today with wonderful people of Texas Solar Power Company. Yamaplos 15:00, 24 April 2008 (EDT)

• wire things together

done. It works!

well, sort of. It appeared to work, but actually kept discharging

Actual charge as of yesterday Yamaplos 15:43, 21 May 2008 (EDT)

tests log

Space reserved to report on what happens.

Uh, need to clean up things. add some schematics. when I'm back from Camp Texas Yamaplos 09:29, 25 April 2008 (EDT)

CIS PVs

New era CIS(Copper Indium(di)Selenide) PVs are arriving,with appealing features & lower prices!

People

please sign in. Being in this list just might give you first dibs as XO Solar stuff starts to get distributed !

If you don't have a User page in the wiki with contact info, please contact me by email so I can touch base with you!

Yama Ploskonka contact for the project, yamaplos@BOLinux.org

buxtor would like to be on the XO Solar list!

Doug LaRue has some tech(hard/soft) backgound

Nicholas Schaefer has free time and an XO-1

Ron Lussier Looking for a power solution for a Fijian island which has no power access.

Stan.SWAN in Wellington,NZ has made significant mid 2008 (yes-NZ winter!) XO charging testing with a 10W CIS (Copper Indium Selenide) PV. Such CIS/CIGS PVs are cheaper than normal Si types,& show superior overcast/haze/low light & off angle output. Automotive 12V SLA based emergency "Portable Power Packs" (~US$35) were found ideal for solar storage. stan.swan@gmail.com

Nick Thompson nickpthompson@gmail.com would love to get any sort of solar XO action going on!

swannjie@gmail.com Click on edit to enter your information here

special thanks to

• Anne Gentle from XO Austin, for trusting me with her B4 XO, even after I told her I could not guarantee it would not fry.
• Graham Knight for good technical advice.
• Mike Lee, for encouragement and helping me lose some of my noobishness in XO power issues, so that I could sound more like I knew what I was talking about, when corresponding with more expert people.

got the plugs today. Thanks! They're the real thing! Yamaplos 11:48, 1 May 2008 (EDT)

• Craig Overmiller and the people of Texas Solar Power Company, for encouragement, expert advice, and a battery.
• Richard Smith, EC, battery, and power guy for OLPC, for expert advice, encouragement and assorted words of wisdom.
• Wayan Vota of OLPC News and his never satisfied visitors :-), that just couldn't leave solar for XO as something that could wait some more, which eventually got me going.

Location

XO Solar is based in (right now partial cloudy) Austin, Texas