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W6KWF > EMCOM 01.05.20 16:17l 63 Lines 3520 Bytes #999 (0) @ WW
BID : 26171_W1XSC
Read: GUEST
Subj: Small 12VDC Solar Power Setups
Path: IW8PGT<IZ3LSV<IR1UAW<I0OJJ<N6RME<W1XSC
Sent: 200419/0021z @:W1XSC.#NCA.CA.USA.NOAM [Santa Clara Co] #:26173 $:26171_W1
Greetings,
I was recently asked for recommendations on small 12V solar setups, and
thought that others might be interested in what I wrote. I used to work
as a solar cell applications and test engineer at a solar cell startup,
before that company, like most companies working on novel solar cell designs,
went out of business and I had to move on.
12VDC Solar system design is an entire rabbit hole of design choices,
so making a specific recommendation is never easy, but my usual go-to
recommendation for people getting started is something like the following:
Mono-crystalline panels are easily available on Amazon, and I've always
heard good things about Renogy, so look at their 100W panels as a starting
point: https://amzn.to/2ymHZH4 - Expect something like $1.20-$1.50 per Watt
for retail single panels.
You may want to go bigger depending on how much you want to run for how long,
but a 100W panel in good light will get you about 200Wh-500Wh per day, so
figure out how much energy you'll want and multiple accordingly.
For batteries, for a long time I've recommended Lead-acid AGM deep-cycle
for amateur radio operations. Remember that car batteries are "starter"
batteries, so they're not designed to deliver a large amount of energy over
a long time, but a short burst to start your engine and then immediately get
recharged. Flooded lead-acid batteries are marginally cheaper per Amp-hour,
but really only make sense in a static deployment where you definitely won't
want to move them, and have them in their own container to deal with their
off-gassing. AGM batteries are sealed, so they're much more attractive if you
every thing you'll want to transport these batteries, such as taking them out
to field day.
https://amzn.to/34NKtue
Lithium LiFePO4 batteries have come down quite a bit in price recently, so
while they're still much more expensive than lead-acid per Ah, they have a lot
of upsides and may make sense if you're planning on cycling your batteries more
than a few hundred times, or want to pay extra to reduce weight. For off the shelf
solutions, I'd look at Bioenno's line of batteries; they even have models which
come with Powerpoles on them. I bought one of their 20Ah batteries with their
charger and put them in my own box, and have been very happy with them:
https://www.bioennopower.com/collections/12v-series-lifepo4-batteries/products/12v-20ah-lfp-battery-pvc-blf-1220a?variant=18426
900421
You will also need a solar charge controller to connect the solar panel to
the battery to correctly regulate the panel voltage, and many come with
a "load" port so they can protect the battery when you discharge the battery
so they disconnect your loads to prevent further damage.
With the typical "12V" (really about 18V) panels like I linked above,
it is possible to get extremely cheap Pulse Width Modulation (PWM) controllers,
but I've always been a huge fan of the EPEver controllers, since they
support maximum power point tracking (to get the most power out of your
panels regardless of current light level, battery voltage, etc) and are
flexible enough that I've reprogrammed the EPEver Tracer controllers to
correctly charge LiFePO4 batteries in addition to the different types of
lead-acid batteries that they are designed for.
https://amzn.to/2yq6xim
So these options may not be the cheapest possible, but for <$600 I think it's
a good start, and many of these parts will still be useful if you decide to
take this system apart and build a bigger one.
Kenneth, W6KWF
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