[aprssig] Emergency Power for Ham stuff

vk2tv vk2tv at exemail.com.au
Tue Jan 19 15:20:45 CST 2016


Bob,

Are you seriously suggesting that hams tap into what is a potentially 
lethal power supply, without warning about the dangers such a scheme 
presents, not to mention the legal implications in places like Australia?

I can understand your desire to pursue alternate and emergency power 
sources but safety MUST come first.

Ray vk2tv

On 20/01/16 07:12, Robert Bruninga via aprssig 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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