[aprssig] Emergency Power for Ham stuff

[Robert Bruninga]

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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