Prepping 101: Survival Computing on 12 Volts

by Paul Helinski on May 8, 2016

Resources:
12v – 19v / 5 amps Step Up Converter in Metal Chassis $18.23
Same Thing in 10 amp Model – $16.50
Adjustable Power Supply 80w – $12.50
100 amp/hour Sealed Lead Acid Storage Battery – $169
100 watt Solar Panel – $114
Charge Controller 30 amps – $40
5v/3amp Converter w/2 USB Ports -$3.05
5v/3amp Converter in Video w/2 USB Ports $3.50
5v/5amp Conerter in Metal Chassis $8.99
10 Pack 3a Buck Converters – $22.99
Raspberry Pi Information
The Pi on Ebay
It has been a long time since my last topic on solar power. Not much has changed. A basic solar system is still made up of panels, a charge controller, and storage batteries. It’s not rocket science, and the prices haven’t lowered significantly, except perhaps in storage batteries.
I did, however, find and tested something of late regarding power that I think I should share with you. It is survival computing. Most people think of computers, even laptops, in terms of wall socket, AC power, but they run on DC. That one of two functions of your power adapter, converting AC into DC, which on a laptop then charges your battery, and the laptop runs off of the battery. Desktop computers also run off of DC, and they have an internal power supply that does the same thing as your laptop adapter, but for this article we are going to stick to laptops, and other portable devices.
In general I am not a big fan of power inverters. They are always going to be your point of failure in a solar, wind, hydro, or thermo power solution, and they should be avoided whenever possible. I think you should run as much off of 12 volts as you can, but there are a lot of benefits to having a laptop available, and phones and tablets are priceless if you have kids. None of these will run off of pure 12 volts, so you will need a power inverter. The nice thing is, your batteries are DC and the computers run on DC, so half of the inverter isn’t required (the oscillator, to make the power AC). The other half, the part that changes the voltage, is much simpler as well. Instead of ramping 12 volts up to 120 volts, you only have to message the voltage up to 19 volts in the case of laptops, or cut it down to less than half for all of your 5 volt devices.
I’m also going to cover a $25 low voltage/low amperage computer solution that is currently being used to build perimeter security systems, remote listening posts, and even balloon lifted radio relay antennas, and that also runs on 5 volts. It is pretty cool stuff.
To focus down a bit first, my topic for this week is specifically about what most people call “buck converters,” or “step up/step down transformers.” They are made to lift or drop fairly low voltages to a percentage increase, or decrease. For this article we are looking at converters that will take 12 volts as a source (actually 13.6 or so on a regular deep cycle storage battery or car battery), and convert it to either 19 volts or 5 volts. This is DC to DC, remember.
Even though I am something of an electronics nerd, I haven’t looked into the actually schematics for these things. It appears that they use a coil and control circuits to work some low level voltage magic, and though the boards are full of components, they are cheap cheap. Some units have a variable resister pot to control the output voltage, and some are dedicated to a certain voltage, and come encased in a weatherproof and shockproof chassis.
The most common voltage for laptops is 19 volts and most of the buck converters are built to appeal primarily to that voltage, with enough power to cover the draw of most laptops. My current Lenovo power supplies say 20 volts, but if you open up the case, the actual internal battery is listed as 19.4 volts. For consumption, usually the power supplies will list a wattage rating of 60-100 watts, or they will say 3-5 amps, which at 19-20 volts is 60-100 watts.
When you buy a buck converter, the variable voltage models generally are listed in watts, and the fixed voltage ones are listed in amps. I have focused on the 60-100 watt range for this article, but they are now listed on Ebay for up to 200 watts, and even higher occasionally. For most single laptops this is overkill, but I do have a beast of a Dell that is several years old and that has a 7.7amps@19.5v power supply. That is 150 watts.

Fixed vs. Variable Voltage

When I first purchased these they were much more expensive, so this decision isn’t as important as it once was. The 12v to 19v converter that you see in the video, rated at 5 amps, used to be $40. Now it is $18.23 with free shipping. The 10 amp model is even cheaper than that these days, linked above.
The adjustable supply with the voltage readout is only $12.50 with shipping. To me it is a no brainer to buy one of these as well, because you never know what you might need to charge down the line. The Canon camera that I shot the above video on has an 8.4v power adapter. When the wall socket goes down for good, I may want to document what happens next. You also may want to run a wireless network, charge a remote control car for your kid, or play your guitar through a signal processor and headphones. A lot of things run on odd voltages and come with those odd voltage wall warts. Clip off the wart, dial in your inverter, and start shredding away.

Charging Phones, Tablets, GPS, etc.

The nice thing about all of our nifty devices that clutter up our lives these days is that most of them have long lasting internal batteries, and they all charge on 5 volts. There are dedicated solar charging devices for them, and even thermal ones as I have reviewed in the past, but the problem is, the capacity of those batteries is really small. In solar panel terms it isn’t worth charging the devices directly, because they’ll be fully charged with the sun still shining using a real solar panel, and the gimicky backpacker solar chargers are a complete waste of time. You’ll pay as much for a small 2-3 watt designer solar panel that is rigged for 5v output as you will for a 40-100 watt real 12 volt solar panel, and if I were you I would opt for the real panel and real storage.
The battery you see in the video is a generic sealed lead acid 100 amp/hour model that goes for $169 shipped. If you are careful to not run it down past 50%, it should last years, if not a decade. 50 amp hours (half) equals 680 watt hours at 13.6 volts, (which it won’t hold for the entire life of the charge), but even if you say 500 watt hours, if your laptop is drawing a high amount, like 100 watts (which is most likely double what it really draws), that equals 5 hours. In practice it will be more like 12 hours.
To refill 680 watts, using a 100 watt panel, you should be able to match that in about one day worth of daylight, assuming some direct sun. But even if it takes a couple days, or a few days, or even a week, that much use out of a computer if you are using it as an RTL-SDR receiver, or with your Ham radio, or even just to watch movies, is pretty darn good. A 100 watt solar panel right now is as little as $114 shipped. The 30 amp charge controller you see here in the video is $12-40.
The buck converters for 5 volts are even cheaper. In a waterproof case with two USB ports pre-wired, the whole thing is all of $3.50 shipped. This will charge your phone or tablet just as fast as nearly any wall charger, and the input circuits of those devices generally limit the input to 2 amps at most regardless, so more amps isn’t going to charge you quicker. I have also linked to a 5 amp model meant to be mounted in a car and hard wired to mounted USB ports in the dash. I charged the dead dead Ipad you see in the video from that 100ah battery and it used about 1% of the charge.

The Raspberry Pi

I feel that I would be remiss if I failed to mention the newest revolution in computer technology for this article. It is called the Raspberry Pi, and it is a $25 full featured computer based on the Debian Linux operating system. Right now they are a little more expensive that that because they can’t make them fast enough and they are going for a premium. There is even a $5 Pi now (though I haven’t gotten one or tested it) and I just saw one being bid up on Ebay to over $25.
I call it a revolution, but it is more of a counter-revolution. Because going on 30 years, computing has been the battle of the stupid between the PC and the Mac. Apple is one of the most profitable companies in the world today because they have succeeding in making computer devices that are almost entire idiot-proof.
Well not of us are idiots, and some of us would even prefer to teach our kids to not be idiots. That as the idea behind the Raspberry Pi. Build a cheap, basic computer with enough power to do most stuff for a cheap cheap price, so that kids could use it in a classroom setting as a software and hardware development learning tool.
In a very inexpensive package, the Raspberry Pi was created to break out the things that the hardware of a computer can do into usable chunks, and with each of those chunks you can program everything from lighting simple LEDs, to running a sensor network, to controlling a robot army.
Google around and you’ll see some of the incredible things that people have done with this little $25 computer. In practice it isn’t really $25, because you have to buy a memory card, a wireless dongle, a keyboard, a mouse, a screen, and an HDMI cable. It will run on any TV, so you may be able to save money on the screen to get started.
What makes the Pi unique, (and it isn’t unique these days because there are a few good copies), is that you have access to all of the ports, and what they call GPIO pins, which are control points that you can program. I’m not going to get into the depth of the Pi, but you’ll see that people have used it for all kinds of nifty things that directly pertain to perimeter security, communications, and remote activation of electronic defenses. Based on a “system on a chip” originally designed for TV set top boxes, the Pi isn’t a ton of computing power, but you have complete access to everything that a computer can really do.
There is also a new version of Windows 10 that runs on the Pi, but it is experimental, and traditionally the Pi runs a special version of Debian Linux called Raspbian. For serious tasks you’ll be using the Python computer language, which isn’t that different than Perl, the original language of the web that GunsAmerica, Ebay, Amazon, and all the other first generation automated websites were built from. If you have any programming experience at all, Python should be easy, and when you see how cheap you can get some very serious sensor boards, relay boards, and even Arduino control boards for these days, if you have the time you’ll be digging in I can assure you. These little computers are truly modern wonders of technology.

What Can I Do With This Computing Power?

If you didn’t see my article on RTL-SDR, you should read it now. It is from last year, so there is no accompany video. We take communication and information for granted, but after this whole mess burns down and evolves into chaos, there will be neither. I think the powers that be will try to keep the Fox News et al propaganda machine on as long as possible, but at some point everything is going to go dark, simply because the supply lines of food are going to fail.
An RTL-SDR radio is not unlike the Pi (though the Pi is not powerful enough to run the graphical software, but people do use Pis to transmit raw data from balloon antennas to laptops on the ground). The RTL-SDR took something we consider simple, like turning on a TV, a little more complex, but with that complexity (really not more than installing software and learning something about antennas), that in turn made the technology more flexible. This brought an enormous power to really use the simple technology (in this case it was a laptop TV dongle chip) to give you what could only be achieved by expensive systems before.
You can “watch” huge swaths of radio bandwidth with an RTL-SDR for any audible signals. Think about this in contrast to even an expensive Ham radio, which is limited to certain frequency blocks anyway. On a Ham radio, unless you use it’s computer interface, you can listen to about 3,000 hertz at a time. With an RTL-SDR and a decent laptop you can watch and listen on 2,000,000 hertz. Prior to this, you needed an expensive modern Ham radio, interface cables and more knowhow than it takes to get the RTL-SDR going.
You can also monitor radiation levels while you are sleeping with a laptop and some of the USB Geigers I have covered here, and don’t discount the value of entertainment in a survival situation. A 2 terabyte drive right now is about $60. You can put hundreds of movies on one drive, tens of thousands of books, fiction and nonfiction including encyclopedias and how to books for just about everything.
Tablets and phones, primarily the Android devices, are also valuable for entertainment, and if you have kids, the games will for the most part work off of the network. I have also covered a network free GPS topo map you can buy for Android, and there now both Ham radio and RTL-SDR apps you can get for Android. This is no joke stuff, you just have to learn to use it now, before the collapse.
That is why I suggest you do take some time and download the RTL-SDR software, buy a couple of good antennas, get a good Geiger, and get busy downloading movies. If you have time for the Pi, go for it. There are dozens of uses for sensors and relays in a survival situation. But you have to get going now. You know they say there only two times in your life that it is wise to plant a tree. Thirty years ago and right now.