[NLRS] Solar panels- Update

[Tom Peterson]

It's a very good price, even compared to some of the homebrew projects 
I've looked at.  20W is just a starting point.  I intend to add to that 
over time and additionally, add some wind generated power as well.  I 
don't plan to attempt to run the whole house, just the shack.  I did a 
little experimenting over the winter months running things in here off a 
pair of deep cycle batteries.  I was able to run things to my satisfy my 
needs using a 2 amp charger for a few hours a day.  Perhaps if I was 
retired and ragchewing on 75M or if I did my contesting with something 
other than an Icom 703 I'd need more power capability.

I expect that I could do without a charge controller with the size of 
battery I'm using and doubt that I'd ever boil the battery dry, but 
again, at some point, I plan to add more capacity.

Doug Reed wrote:
> I feel I must point out that a 20 watt panel provides only a 1 to 1.3 
> amp charge rate. But $110 for a 20 watt panel is a good price.
>
> During the summer, with 12 or more hours of sunlight, you can expect 
> about 14 amp-hours of effective charge.
> During the winter, the solar insolation guides suggest planning on a 
> maximum of 4 to 6 hours a day of sunlight and therefore a maximum of 7 
> amp-hours effective charge.
> The daily effective charge rate is a good indication of how much power 
> you can draw on a daily basis. Any more than that and your battery bank 
> will eventually be dead.
>
> This panel was obviously designed as a standby-backup charge source for 
> a camper or other battery system like at a cabin. It will keep the 
> batteries up to max and even run a very small continuous load, probably 
> about what a charge controller would draw.  :-)   But one small panel is 
> not enough to recharge that battery system if it is being used on any 
> sort of regular basis. Panels for whole-house solar collector systems 
> are usually counted in 1000's of watts, not 10's. Although for a small 
> cabin used once or twice during the winter, it might still be enough to 
> keep the batteries up.
>
> For Field Day, I've considered using a small solar panel to claim "solar 
> powered" by charging a deep-cycle battery bank over a couple weeks. The 
> size of the batteries depends how long you intend to operate and the 
> size of the station. Field Day is short term and low power is still useful.
>
> For what its worth, the simplest charge controller for a small solar 
> panel has:
> 1. A heavy diode to isolate the battery from the panel.
> 2. A voltage comparator on the battery side that trips at the maximum 
> charge voltage for the battery bank.
> 3. A large FET or NPN transistor configured to short the solar panel 
> when the voltage comparator is triggered.
> The simple charge controller simply SHORTS the panel since that gives 
> the lowest power dissipation. If it diverts the power into a resistor, 
> that means it must dissipate the full 20 watts. This type of charge 
> control is only used for small panels since large panel arrays have much 
> higher currents.
>
> As an alternative, Harbor Freight sells a 45 watt solar PV panel kit for 
> $220 and sells a 75 watt panel for $500. The 45 watt kit has some extra 
> items to sweeten the deal. They even have some charge controllers for 
> $30 to $80. But remember, the 45 watt kit is at best around a 3 amp 
> charge rate.
> <http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=90599>
>
> And there are a number of videos on YouTube that show mounting solar 
> panels and even assembling solar panel assemblies from individual 
> monocrystalline solar cells. And additional videos that talk about 
> wiring and battery installation. I'd suggest using the videos for a 
> quick introduction to the project but then follow up with a lot of your 
> own research on the Internet and at the library. (I don't trust the home 
> videos very much.)
>
> 73, Doug Reed, N0NAS.
>
> Tom Peterson wrote:
>   
>> Well it's not quite the end of the day and there is still a little 
>> usable light, but I've disconnected the panel and brought it in for the 
>> night.  The final reading isn't what I expected.  11.9V.  I went out 
>> about 6PM and it was at 12.1V, so there was some increase in stored 
>> energy.  I solved the puzzle in short order though.  The battery that 
>> I'm charging is connected to my camper.  My 7 year old was out there 
>> watching a DVD with a friend, using the portable DVD player, but it 
>> seems they felt that they needed one of the interior lights on. 
>> Additionally, my yard is heavily shaded by trees.  I think I'll try this 
>> again later in the week and disconnect the battery from the camper and 
>> position everything where it can receive direct sunlight without any 
>> leaves blocking it.  All in all though I think it was a good purchase 
>> and with some wind generated capacity and a few more deep cycle 
>> batteries, I should soon be able to take my shack off grid completely.
>>   
>>     
>
>   
>>   
>>     
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