So for a change-of-pace from some of the recent political upheaval, let's do an informational thread on how to build a small-scale solar system.  If any of the concepts are unfamiliar, please refer to the "Cabin sized solar system" thread in this same sub-forum. 

 

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

Original Post

This system is very simple:  PV panel(s), one battery, a charge-controller, and a couple of 12V devices.   This particular setup will power anything that takes 12VDC, with the runtime dependent entirely on the watt-hours of energy of generated vs consumed (and number of cloudy days).   Various DC-to-DC convertors could be added to such a system to power devices that take a different voltage, but it's all-DC; there is no inverter in this system. 

Something on this scale would be ideal for a small camper, trailer, or remote autonomous device (like a Mighty Mule gate opener that doesn't have grid-power available, a trail camera, weather station, etc). 

Let's start with the equipment list, and build from there (curse you, Jeff Bezos... for your convenient one-stop-shopping):

Charge Controller (the most important component):

https://www.amazon.com/Victron...roller/dp/B00U3MK0CI

Panel (generic, choose whatever wattage you want):

https://www.amazon.com/Newpowa...e/dp/B01LY02BOA?th=1

Battery (again, generic... just make sure it's a "deep cycle" battery):

https://www.amazon.com/Vmaxtan...erters/dp/B00DDYM1UC

 

Let's begin with the charge controller.   This device is the hub/brain of the entire system.  It takes the energy from the panel (in the case of the one I linked, it's 17VDC at about 6 Amps), and efficiently converts it to whatever charging voltage your battery requires. 

There are three sets of screw-down terminals, going from Left-to-Right:  Battery, Solar (PV), and Output (Load). 

Here's what it looks like in actual use. 

Note the "Load" terminals on the right.  They are sending juice to a 12v-to-48v PoE converter.  There is an additional set of wires (blue and brown twisted-pairs) that connect to the same green terminal block, and send the 12VDC to another device (a wireless bridge).

I have the "Battery" leads in my hand (connected with Anderson Powerpole connectors to easily remove the battery, if necessary): 

The "PV" (solar panel) leads are connected to MC4 connectors:

There are various pre-built charging "profiles" in the controller based on battery type, so you can pick one that most closely matches your battery, or pick your own custom values.   One of the best features is the 12VDC output that can run small loads.  It helpfully tracks all the energy that is passed through it, so it can give you an idea of the energy "balance" (generated versus used) of your setup.  You can adjust all of this from an app on your phone, provided you're within about 50 feet of the device...  super-convenient.

It was originally connected to a basic, 100W panel.  

 

I found this was not enough, since this rig only gets sun about half the day.  I added the second panel (the larger ground-mount panel is a 240W panel), and it hasn't run out of juice since.

 

The battery is a 155Ah AGM lead-acid battery.  One is pretty much as good as another... this one was re-used from another application:

 

If you happen to have an old car battery laying around, you could get into a system like this, and experiment with it, for about 2-300 bucks-and-change.   I'd recommend doing that before you start buying expensive batteries, because the rule-of-thumb in solar systems is that you learn all your hard lessons from your first battery bank (and usually end up killing it prematurely).  Only go expensive on your SECOND set of batteries. 

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

So something of this size has a lot of practical uses, in addition to being a great way to get your feet wet with solar.  With enough sun (and sufficient panels to replenish your daily watt-hour usage, planning for some cloudy days), this thing could run indefinitely.   Whether it's a large or small system, the concepts are the same; you just scale everything up-or-down. 

You could mount this thing on the roof of a hunting blind, a kid's tree-house, on a telephone pole, or gate-post (they make post-mounts for panels up to about 150W panels... the very large panels don't usually have single-pole-mounts). 

This one is powering a driveway camera on my farm:

The video is sent back to a video display in a building a couple-of-hundred yards away, through this wireless bridge:

That's an old Ubiquiti Locostation2 that I recycled from an older installation (Ubiquiti wifi hardware is a great value for the $$$; this one spent YEARS out in the elements, and still works).  It's a 2.4 GHz wifi device that can act as an access point, or a bridge.   A zip-tie to hold it onto that 4x4 post is the only mounting hardware it required.   It's in bridge mode here, and connects to an existing access point in the building. 

It uses something called "passive PoE" for power.  Passive PoE is distinctly different from regular 802.3af-spec PoE.   Regular 802.3af PoE is 48VDC, and is the voltage delivered by standard Netgear/Cisco/Ayava/Trendnet/whatever ethernet switches.  

PASSIVE PoE is lower voltage, usually 12-24VDC... so plugging this device into a regular PoE network switch will NOT work.  It will refuse to power up, because the voltage is too high. 

In this case, we simply made a custom cable.  It takes its voltage over two of the four twisted-pairs (positive on the blue pairs, and negative on the brown pairs).   You crimp the far end of the cable like a normal "B" type ethernet cable... but on the power-end, you split out the blue and brown pairs, and place/crimp the orange and green pairs like a normal "B" cable (same slots in the RJ-45 end).   You can see it in the pic below:

The wifi device you see above takes 12VDC.  Newer versions of the Locostation2 require 24VDC, so you'd need a DC-to-DC convertor to go with the wifi device... pairing the two items below would do the same thing:

https://www.amazon.com/24V-Boo...former/dp/B07XBWHR56

https://www.amazon.com/Ubiquit...utdoor/dp/B00DCNRTAG

 

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

So here are some configuration tips for the ubiquiti bridge (**WARNING**  Math incoming).  

This assumes you already have a wifi network somewhere, and you want to send the signal/data from the remote solar-powered end (whether the device is a camera, weather station, etc) back to your home wifi.  The remote end of the connection is the Ubiquiti device, and could be at the end of a long driveway, in a barn or shed, etc.  You just need line-of-sight, and preferably a little elevation... I'll explain below.

First you should understand the Fresnel Zone.  The Fresnel Zone is named after the 18th-century French engineer and physicist Augustin Fresnel, whose did groundbreaking work on the diffraction of light.  He also invented a lensing system for lighthouses.  Even though he died at age 39 of Tuberculosis, his groundbreaking work in the field of optics (and his lighthouse lenses) literally saved tens-of-thousands of lives.  The "Fresnel Zone" is named in his honor.

It describes a lens-shaped ellipse that extends from one antenna to another... and generally requires 80% clearance (without obstructions) for the best signal strength.   60% clearance will SOMETIMES work... but with degraded signal.

It looks something like this:

You need to know the radius of the Fresnel Zone at the center of the ellipse (the midpoint of your signal path) so you know how high your antenna needs to be mounted.  This will vary not only with distance, but with the wavelength of your signal.   A lower frequency will have a larger Fresnel Zone.  For instance, a 200-yard distance in the 2.4GHz band will require an antenna height of eight feet.  The same distance in the 900MHz band will require an antenna height of thirteen feet. 

There are online calculators for this.  You can plug in numbers, and see what you need:

https://www.everythingrf.com/r...snel-zone-calculator

The signal strength on this Locostation is great, even though it's communicating with an access point inside a steel pole-barn.  This is because it has a directional panel antenna, making it a literal wifi cannon (and the access point in the barn has a very large, high-gain, omni-directional antenna)... but also because it's about 12 feet off the ground, giving it a totally unobstructed Fresnel Zone (no trees in the way). 

Note the signal strength bars below (you can barely see them... we're at four bars):

The other thing to understand is which wifi bands are obstructed by which materials.  For instance 5GHz wifi has a very short wavelength, and a small Fresnel Zone, so the antennas don't require much height... but the signal is easily degraded by common materials (like wood).  2.4GHz has better penetration, but has a larger Fresnel Zone, so the antennas need more elevation, and it is degraded significantly by water (particularly vegetation, like trees).  900MHz has the largest Fresnel Zone, so the antennas have to mounted even higher... but it does NOT care about trees; the signal punches right through. 

Everything is a trade-off.

To get one of these devices to "bridge" your network at the remote end to your home wifi network, you have to pay attention to a couple of configuration fields:

First, you can look at the main tab... dat signal strength tho...

Now we move on to the "Wireless" tab (next one, from left-to-right... look at the top).

Wireless mode needs to be "Station."  The Wireless Security settings on the bottom need to match the ones on your wifi router EXACTLY.  If the central router is WPA2-PSK, then that's what you select on the remote end.  If it's WPA2-AES, then pick that.  Make sure it matches. 

Now we move on to the network tab, (next one from left-to-right):

Network mode needs to be "Bridge."  This means the device will "Bridge" your remote network to your central network.  Think of it like a long ethernet cable, made out of radio-waves.  I like to give these devices static IP addresses, so I know where to find them in case I need to make configuration changes... so I picked "Static" for Bridge IP Address.  Make sure this IP address is of the SAME format you get from your home wifi router.  If  in doubt, open a DOS window (or Command Shell) in windows, and type "ipconfig"

Look at your Wireless adapter IP address.  It should be some form of "192.168.x.x"

Make sure everything in the IP address you choose for the remote bridge matches that of your computer EXACTLY, except for the numbers after the last decimal-point. 

For example, if your computer's IP address is 192.168.1.173, then pick something like 192.168.1.30 for your remote Ubiquiti bridge.  The subnet mask should be 255.255.255.0 

If you do this, your bridge should be able to talk to your home network, and you should be able to access the network devices at the remote end. 

If you don't think you will ever need to make configuration changes, you can simply pick "DHCP"... that will also work, and you don't have to know all the IP-address stuff.

That's the quick-and-dirty version of how it works. 

If you do it right you end up with something like this:

That's a screenshot from that solar camera.   I can see when anybody shows up.  It also sends me emails if it picks up motion when I'm not there... a great security measure. 

I'll take any questions.

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

Bill, Idaho posted:

I am guessing weather does not affect it very much?

The wireless link?  Not at all.   You can have an absolute frog-strangling rain coming down, and it never drops out. 

Sufficient rainy days would run down the battery eventually, but the solar panels produce power even on cloudy days... it's just not enough to keep it going indefinitely (it would be if I went total overkill on the panels). 

On a very overcast day, your solar panels might put out 10-20% of their rated output.  That's not nothing, and helps offset some of the power drain.    A single sunny day replenishes it entirely.

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

Also, when it comes to signal propagation, whether it's wifi, ISM band, VHF... almost doesn't matter.  When in doubt, don't crank up the power... either add height, or get a better antenna.  

There are very few radio problems that can't be solved with better antennas.   

******** Edit *********

Just so everybody better understands the antenna thing...

A standard whip antenna that everybody recognizes from their TV, vehicle, or the radio on their belt is an "omni" antenna.  It's the most common form of antenna, and radiates (horizontally, anyway...) in every direction .

There are also directional antennas.  These radiate their signal in a specific direction, and there are all kinds: Yagis, Panels, Waveguides, etc.  The most common example are the "sectorized" antennas that you see on virtually every cell tower in existence.  They are the tall, vertical thingamabobs you see mounted on the ring or stand-off at the top of the tower.  On a standard three-sided tower you'll see 3-4 on each of the three faces of the tower.   These don't radiate their RF energy in every direction... they only radiate in a narrow sector... maybe 15-30 degrees.  If you have a dozen 30-degree sector antennas on a tower, you can cover 360 degrees, and use separate transcievers for each one to increase bandwidth. 

The Locostation wifi device I linked up-thread is a Panel antenna.  These are also directional, and mostly used when you want to throw most of your signal (transmission AND reception) in a single direction.   It increases your antenna's gain (and consequently its performance) when you point your panel towards your endpoint.   These are ideal for point-to-point links... or mounted in the corner of a large area to cover the direction it's pointing.

The radiation pattern looks like this:

If you have sufficient height, you can use a panel like that to set up point-to-point links with distances that are measured in MILES.  

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

rhunter424 posted:

Great thread.

Any concern/advice about batteries in weather conditions? Precautions when charging/using below freezing?

Depends on battery type.

Lithium batteries don't like to be below freezing... charging them when frozen can kill them, and lead to nothing but tears and lost money.  You can, however, DISCHARGE them when frozen... which will sometimes generate enough internal heat to allow charging (which also generates heat).   Most Lithium batteries have a BMS (Battery Management System) that protects them by shutting them down when it's too cold.

Lead-acid batteries can also freeze in extreme conditions, but it's gotta be pretty friggin' cold to freeze a fully-charged battery (a discharged battery will freeze MUCH more easily, because a discharged battery has less sulfuric acid in solution... remember that any solute in an aqueous solution causes boiling-point elevation and freezing-point depression... it's why antifreeze works, and salt melts the ice on your sidewalks). 

If you're in that kind of extreme environment, consider getting a battery blanket (or a battery heater... which is usually just a 30W resistive heater that attaches-to/wraps-around the battery).   Amazon has them.

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

HomoSepian posted:
rhunter424 posted:

Great thread.

Any concern/advice about batteries in weather conditions? Precautions when charging/using below freezing?

 

If you're in that kind of extreme environment, consider getting a battery blanket (or a battery heater... which is usually just a 30W resistive heater that attaches-to/wraps-around the battery).   Amazon has them.

This is excellent advice. The existing battery can power the heater enough to keep the battery happy. I think -20ºC or 4℉ is about the point where most of the batteries really start to suck and damage themselves from the testing I've done. Once we introduce any type of load at those lower temps, the battery is "awake" and doesn't mind the cold. You might need a little more solar panel coverage to offset the draw from the heater, which will primarily occur and draw down your batteries when it's dark or crappy out. 

geronimo posted:

This is excellent advice. The existing battery can power the heater enough to keep the battery happy. I think -20ºC or 4℉ is about the point where most of the batteries really start to suck and damage themselves from the testing I've done. Once we introduce any type of load at those lower temps, the battery is "awake" and doesn't mind the cold. You might need a little more solar panel coverage to offset the draw from the heater, which will primarily occur and draw down your batteries when it's dark or crappy out. 

And to save a few watts, you can use a thermostatically controlled switch to only turn on that heater when it's needed.  Just put the thermostatic switch in your battery box, and run your battery blanket/heater off of it.

You can find them for AC:

https://www.amazon.com/Farm-In...rolled/dp/B0006U2HD2

 

Or DC:

https://www.amazon.com/Thermos...Flange/dp/B0026S6WGK

 

“One sometimes gets the impression that the mere words ‘Socialism’ and ‘Communism’ draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, ‘Nature Cure’ quack, pacifist, and feminist in England,”  -George Orwell-

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