[Power] [support-gang] solar power design for 5-to-10 XO-1 laptops in Haiti (or elsewhere!)

[George Hunt]

I'm concerned about the battery you're planning to use.  The small UPS
batteries are usually 9AHr -- or said differently, can nominally store 108
watt hours.  Each XO1 battery requires about 30 Watthrs.

And lead acid batteries should not be completely discharged, or they last a
very short time -- maybe much less than a year.

So, say you had 5 hours of really good sun, and you got 80 watts from your
panels.  You'd need to store 400 watt hours of energy.  The battery you're
planning to use will not do what you need.

I am imagining that a "charger squid/bank" might include the MPPT
controller, and the small battery to limit the voltage applied directly to
the XO's (with the help of the MPPT controller, and it's DC-DC converter).
The power from the solar panels will pass through the controller, go
through a dc-dc down conversion, for the most part bypass the lead acid
battery, and charge the XO's.

There is no low voltage cutoff, or even any voltage readout on the
controller.  I'm thinking that we nead a creative way to prevent excessive
discharge of the battery. (I understand that UPS devices will quit when the
voltage goes below 11.5. But  the level of discharge is better indicated by
a combination of voltage and current.

George


George


On Tue, Jul 23, 2013 at 7:27 PM, James Murdza <james.murdza at dresden.us>wrote:

> Thanks all for the outstanding amount of information. I think I will try a
> setup like so:
>
> UNISOLAR PVL 136 Watt 24V Panel<http://www.ebay.com/itm/UNISOLAR-PVL-136-Watt-No-PeelNstick-SOLAR-PANEL-UNI-SOLAR-PVL136-PANELS-144-128/380679951769?_trksid=p2047675.m1850&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D11%26meid%3D62274773925413104%26pid%3D100011%26prg%3D1005%26rk%3D1%26rkt%3D5%26sd%3D231001584764%26>
> ->
> MPPT Tracer1210RN Solar Charge Controller Regulator 12/24V INPUT 10A<http://www.amazon.com/Tracer1210RN-Solar-Charge-Controller-Regulator/dp/B008KWPGS6/ref=sr_1_5?ie=UTF8&qid=1374553109&sr=8-5&keywords=solar+controller+mppt>
> ->
> 12V lead-acid battery. Originally a small UPS battery, but hopefully
> getting something more serious when everything else works and the funds are
> there.
>  ->
> Directly to a bank of 5-10 XO 1s, using a charger squid/bank that I'm
> putting together myself.
>
> If I order the charge controller in the next 3 hours I can be sure that I
> will get it in time for my trip. Otherwise I'll have to fall back on my 12V
> controller. Please let me know—does this plan with the charge controller
> seem like a safe bet?
>
> Thanks!
> James
>
> On Tue, Jul 23, 2013 at 1:38 PM, Richard A. Smith <richard at laptop.org>wrote:
>
>> So long story short is that if you want to use a PV panel with a voltage
>> that is over about 2x your battery voltage you need a MPPT controller.
>> While the Sunforce controller might work its going to be sub-optimal and I
>> suspect will fail prematurely.
>>
>
>
>
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