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Author Topic: Solar panels  (Read 1229 times)
N2NXZ
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« on: January 16, 2008, 08:33:55 AM »

I run a 10 meter beacon and plan to relocate it to a remote location.It is a converted CB radio and puts out 3 watts RF.It obviously runs from 12VDC and I am guessing maybe 3 amps.I am not sure about the amps and thats where my question is here.If I reduce the power of the beacon to 1 watt out,how many amps would that draw.I am trying to locate an inexpensive solar panel as they are VERY EXPENSIVE as it is that will trickle charge a car battery while the beacon runs 24/7.I had found a few solar panels for charging batteries with regulators for auto batteries but do not want to waste the $ if it will not work.Any info would be appreciated.de Jim,N2NXZ.
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W3LK
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« Reply #1 on: January 16, 2008, 09:20:20 AM »

<< If I reduce the power of the beacon to 1 watt out,how many amps would that draw.>>

Put an ammeter in series with the positive side of the 12v (actually 13.Cool line and measure it.

73,

Lon - W3LK
Naugatuck, Connecticut
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KC0SHZ
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« Reply #2 on: January 16, 2008, 11:44:35 AM »

I use a 12 volt 5 amp hour solar panel to charge a couple of gel-cells that I use for my 718.  I bought my solar panel at Harbor Freight.
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NA0AA
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« Reply #3 on: January 16, 2008, 01:51:19 PM »

First off, you need to determine your actual power consumption by using a meter to measure receive and transmit power draw.

Then you need to calculate the duty cycle of your transmitter - idle vs. transmit per hour - example:  12 minutes transmit at 2 amps, 48 minutes idle at 0.5 amps.  Or:  2 x .2 + .5 x .8 = 0.8 amp/hour

Now you can calculate total amp-hours per day.
0.8 x 24 = 19.2 amp/hours per day.

You need to know how much solar power:  figure on average you will get 6 hours of sun per day, so divide to figure out how many amp-hours you need to make in 6 hours to charge battery.  19.2/6= 3.2 amps charging current.

Double this figure.  6.4 amps x 13.8 volts = 84.48 watts.

I'd go with 100 watts of panel.

Also, use as large a storage battery as you can - two or three large car batteries in parallel might be a good choice to provide plenty of bad-weather reserve.  Old car batteries will do in a pinch, but new deep-cycle batteries will be more reliable if you can spring the $$$.
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AA8LL
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« Reply #4 on: January 16, 2008, 03:57:12 PM »

I'm curious about this "remote location."  Where is it and what is the purpose of the beacon if it's mostly unattended?  
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N2NXZ
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« Reply #5 on: January 16, 2008, 06:42:16 PM »

It is for amateur radio operators to check if 10 meter band is worthy for DX or not.Plus it is an interesting part of the hobby.Lots of information here>
http://www.qsl.net/wj5o/index.html
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N2NXZ
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« Reply #6 on: January 16, 2008, 06:54:28 PM »

Lots of great information from everyone so far.I now realize how expensive this project really is now.Ironically,I did check out harbor freight and I thought that the one that claims it charges auto batteries would be fine.I suppose I need to consider power consumption rate versus how fast it can recharge the battery,especially at night.I really did not think this small xmtr would consume that much before the daylight returned.This looks way too expensive for my taste.I even thought of wind power,but PMA`s are high priced also.HF advertises this panel>
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94543

If I reduced the beacon to 1 watt rf out and used 3 car batts,would it work then?Thats my last desperate attempt here Smiley
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NA0AA
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« Reply #7 on: January 16, 2008, 08:10:44 PM »

The RF output is not the significant factor - it's what the radio is going to draw during transmit that counts - My radios have a flattening curve on power draw vs. rf power output - one radio I have draws 5 amps at 5 watts and will not go lower.

You need to meter your radio to tell.

Another choice might be to scrounge plenty of car batteries and charge 'em from a generator once a week or so.

Solar is not for the faint of heart sometimes.
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ONAIR
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« Reply #8 on: January 16, 2008, 08:58:39 PM »

     You can put in a circuit to periodically turn off the beacon for a few seconds and turn it back on again.  This can effectively reduce the daily power demand quite a bit.  How about the addition of a small generator powered by the wind?
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N2NXZ
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« Reply #9 on: January 16, 2008, 09:52:12 PM »

Yes,since my last post I have discovered some new promising methods.It took tons of research and everyone here helped a great deal.I will share the info here>
http://www.scoraigwind.com/books/marty.htm
Some good stuff here I can try without taking out a bank loan.Thank you all and 73`s.
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K9KJM
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« Reply #10 on: January 16, 2008, 11:21:32 PM »

The advice to simply take a small DC ammeter and measure the draw of your radio and calculate how much power you need is a good one.  Then also take the same ammeter and measure what output your solar panel array will produce.    THEN you need to calculate sunny days vs cloudy days for wherever you intend to install the system.......   You WILL have days when full sunlight is not on your array. Plus, Time of year will make an overall difference in output to your battery.  
I bought some of those cheap Harbor Freight solar panels to charge my battery on an old camper I had.
Worked out well with a few glitches. The panels turned out to NOT be waterproof......  So check that closely. Also the panels were NOT regulated in any way, So even though the output was quite low, They WERE capable of overcharging the battery!  
Some type of automatic cut back is needed with the solar panels I got........
AND I would never consider auto type batteries. Poor choice.  Go with a marine deep cycle type (At the very least)  A brand new marine deep cycle battery is only about 50 bucks, Really not much more than a plain auto battery of the same size.
A better choice would be an AGM type, Sometimes available from big UPS systems, And sold at swapfests.

Your system CAN be done, But it is a little more complicated than just tossing a cheapo solar panel out there...........  
(I have not yet located a good, Reliable regulator system to make the solar panels fully "automatic" and not overcharge the battery, For what I consider a decent price.)
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KE5NWT
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« Reply #11 on: January 17, 2008, 06:39:27 AM »

I found a site about wind and solar that has lots of learning guides and calculators. I have never bought from them and have no idea if their prices are good. I used the site to study solar/wind possibilities for my house and for small loads at sheds, outbuildings,  ect. I determined that the cost was way too high for what I wanted to do. A solar array must have a controller between it and a battery bank. Those little solar panels you plug into your cigarette lighter only trickle charge a maintenance charge into a battery. You have to spend a minimun  of $100 for a panel and $100 for a controller to even begin to recharge a battery bank.
The site is     http://store.solar-electric.com/index.html
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N2NXZ
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« Reply #12 on: January 17, 2008, 08:26:45 AM »

Thank you,I figured about 200$,but most likely it will grow as I go along.I think using the family barn with an outlet is going to be my best hope here.At least there is a Silo for the antenna :)I will check out those sites also as this is an interesting project for me.Thanks again for info all.Jim.
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K9KJM
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« Reply #13 on: January 17, 2008, 01:34:15 PM »

If your new proposed beacon location is anywhere within "striking distance" of commercial power, It will be much cheaper and easier to just run the long cord.......
I have run 120 volt AC power almost 1,000 feet using surplus telephone company "drop wire" This is the very hard plastic insulated #16 gauge copperweld wire that runs from the pole to the house, And phone companies use to go for a few pole spans to reach the nearest junction box. Good for at least 5 or so amps, Which should be more than enough for your beacon.
Find a friendly telephone installer and ask for some used "drop wire"  Something like a case of beer might sweeten the deal........... (This drop wire usually goes right into the dumpster as it has about no scrap value at all)
You could run overhead, Or bury it inside cheap 1/2" roll plastic pipe as "conduit" (If you bury it, Also run a bare copper wire alongside it, Outside the conduit)
Get one of those small branch circuit fuse boxes and use something like a 5 or 10 amp quick blow fuse.
(I would not use a circuit breaker to protect such a long run of wire because of the inductance of the wire)
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N2NXZ
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« Reply #14 on: January 17, 2008, 06:36:46 PM »

I found out today that the silo across the street at my aunts house in unused.A tower with power...lol.With a built in ladder inside it.I dont think I can beat that.Lots of cool ideas on the forum tho.I think I will do it the easy way.I can still play around with wind and solar on a small scale for fun.
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