[aprssig] Emergency Power for Ham stuff

Nagi Punyamurthula n0agi at n0agi.com
Tue Jan 19 19:55:39 EST 2016

I use the Energy Bar 250 for all of my field related ops.  See this :  The unit has input for Solar Power

From: aprssig [mailto:aprssig-bounces at tapr.org] On Behalf Of Robert Bruninga via aprssig
Sent: Tuesday, January 19, 2016 5:30 PM
To: TAPR APRS Mailing List <aprssig at tapr.org>
Subject: Re: [aprssig] Emergency Power for Ham stuff

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

Not a “laptop”, but a “Laptop supply” which can power all kinds of stuff and are readily available by the box full at most hamests and yard sales.
Look carefully for ones at 15v which, with one diode are ideal for charging a 12v battery.  Or go ahead and use a 19v one with a simple $3 DC/DC converter to 13.8b.


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


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