[NLRS] Solar panels- Update

Mon Jul 6 09:18:31 EDT 2009

On the matter of charge controllers, the recent ARRL Handbooks have a
very nice design called the Micro M+.  It utilizes a P-channel MOSFET
rather than an N-channel, so it does not require a charge-pump to
supply the gate voltage, so it is very quiet.  It can handle quite a
bit of current.  I've got one built but not yet adjusted; I had hoped
to be all solar for Field Day but my antenna projects for the June
ARRL VHF contest caused me to fall short--but I think I had my
priorities straight ;o)

I do not know for sure, but it seems very likely that a lot of
commercial charge controllers are going to use the N-channel devices,
since they're a lot cheaper, in which case you may experience some RFI
from the charge pump circuit.  If anybody has experience along these
lines, either positive or negative, it would be interesting to hear
about it.

The kit for the Micro M+ is available here for $36:
http://www.theheathkitshop.com/page24/page24.html.  I just bought
blank PC boards and got all my parts from www.mouser.com which was a
little cheaper when I got everything I needed for three of them.

73,

David  W9HQ

On Mon, Jul 6, 2009 at 5:26 AM, Tom
Peterson<tom at galesvillefiredepartment.org> wrote:
>
>
> 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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