[aprssig] Emergency Power for Ham stuff

Cody Harris qbasicer at gmail.com
Tue Jan 19 15:45:02 CST 2016


A Raspberry Pi with an integrated screen would probably be the best bet for
emergency power, and they're pretty cheap too.

It looks like a Pi could use under 5 watts,
http://raspi.tv/2015/raspberry-pi2-power-and-performance-measurement and be
powered by DC include a 800x480px display:
https://www.raspberrypi.org/blog/the-eagerly-awaited-raspberry-pi-display/

Granted, the size is small, but we are talking emergency use.

Is there particular reason you're looking at powering a full blown laptop?

On Tue, Jan 19, 2016 at 3:12 PM, Robert Bruninga via aprssig <
aprssig at tapr.org> wrote:

> Emergency Power your Ham stuff on solar panels.
>
>
>
> Today I tested  5 different laptop power supplies to see if they would run
> on a 72 VDC solar panel.
>
>
>
> Yes, every one of them would work until the load exceeded the raw power
> available from the solar panel and the solar panels current limited voltage
> crashed.  Most would then cycle, trying to restart until the load was
> reduced to match the power available.  One though, would go to LOW
> impedance and I assume would blow a primary fuse if the DC source had more
> output.
>
>
>
> Note, these supplies are typical universal 100-240 VAC 47-60 Hz and all
> worked down to 72 VDC input (the max-power voltage) of the solar panel.
>   One of them was picky about which polarity was applied to the input cord,
> the others didn’t care.  I couldnt test at lower voltage because the panel
> voltage rapidly goes to near zero when the peak power point is exceeded.
>
>
>
> Reason for this test is the bunch of 40 Watt 72v solar panels I got
> (VOC=100v).  These panels are obsolete, but any 2 modern panels in series
> will easily give several hundred watts at around 72 volts. But when fully
> loaded to the rating of the panels 500W (typical Vp of around 30v each, you
> might want three panels in series giving a full 500W output at around 90
> volts.
>
>
>
> These universal supplies also work on up to 330 VDC input too.
>
>
>
> So, the best tap point on your home solar panels is around 300 VDC
> (typicaly the mid point of a string of solar panels oprating up to 600
> VDC).  These laptop supplies also work just fine on 300 VDC input too
> (remember 240 VAC peaks at 330 VDC).  Taping into your solar array at
> around 300 VDC can deliver almost 1500W from a solar array.  The problem is
> that most of what you need during a power outage do not use universal
> switching supplies, but need 60 Hz power (Well pump, refrigerator, etc).
> But for modern electronics with universal supplies, you’d have more power
> than you need forever.
>
>
>
> Some added detail is on this web page:
>
> http://aprs.org/camp-solar.html
>
>
>
> Bob, WB4APR
>
>
>
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>
>
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