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

[scott]

Hi All,

Please reverse engineer my device from the pictures here:

https://www.solarnetone.org/dojo/terrestrial/emergency-communications-systems/144off.html

It pretty simple.
the batteries are 2 12V 35Ah in series to match the 24V nominal panel.

Enjoy open source:)
Scott


On Tue, 23 Jul 2013, George Hunt wrote:

> 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
> ->
> MPPT Tracer1210RN Solar Charge Controller Regulator 12/24V INPUT 10A
> ->
> 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.
> 
> 
> 
> 
> 
>