Building A Mobile Solar Power Station
by Dan W
One of the more important things we’ve wanted to include with our other prepping supplies is a communication system. Something beyond two cans and a string! Should a catastrophic event occur we don’t expect help in the form of government assistance will be readily available.
Besides, we are leery and don’t think we’d want that kind of help ……….. even if it was offered. At least not until things have shaken out a bit and we have a better feel for what is going on.
However, it will be important especially during the early phase of an event to be able to receive broadcasts (if there are any) to stay apprised of situations both near and far. Forewarned is forearmed!
We discussed just who it might be that we wanted to communicate with, why, and the type of equipment we’d need. There’s a big difference between active and passive communicating. Getting active on the airwaves right away using a radio transmitter did not seem to be a wise thing to do.
Better to stay quiet and attentive while things shake out. The time will come when communicating with those outside your immediate vicinity will not be as risky. Until you know what is going on, why broadcast your presence?
Maintaining communications with those in your tribe is important. If we had to leave our compound for any reason it would be beneficial to stay in close contact with those afield. Small handheld transceivers satisfy this need but eventually, we’d need to be able to actively communicate over greater distances.
A more powerful transceiver of some sort would be needed. We were torn between choosing a Shortwave or a CB Transceiver. These two devices each fill a different function in communications equipment: The Shortwave Transceiver is a long range device while a CB Transceiver is more suited to relatively short range communications.
Setting up and using a shortwave system is more complex than using CB devices. There is a definite need for both types of devices in a complete communications system, but did we want to purchase and set up both types? Would only one type suit our needs?
After much discussion regarding the pros and cons of each, we decided to go with a CB Transceiver as our main unit. Our choice was based on our feelings that we really don’t need to actively communicate with anyone at long ranges (other than listening). To cover all bases we may still purchase a hand-held SW Transceiver at a later date.
We analyzed our needs to determine what devices we’d want to assemble for our communication station. Our “want” list quickly evolved into a “need” list. These are the generic items we settled on:
- A professional quality CB Base Station combined with an excellent antenna system would allow us to reach out across our valley.
- Handheld CB Units (x4) would amplify the flexibility of our base station and give us roving communications capability. We wanted units with rechargeable batteries and an adapter for an external antenna.
- FRS (Family Radio Service) Band Transceivers (x4) for use around our property (short range).
- A multi-band radio (AM/FM/Aircraft/SW + SSB) would be our ears to the outside. This would have to be high quality, high gain radio.
- An emergency frequency scanner that could monitor police, fire & EMS, plus the Aircraft bands; further adding to our ability to monitor what is going on locally.
- A small inexpensive multi-function AM/FM, CD, Cassette player for entertainment. A life without music is unthinkable, so I consider being able to listen to recorded music a crucial aspect of surviving.
These devices would compose our communication and entertainment system. We knew what equipment we wanted to use, but needed to address the issue of how they would be powered? What would it take to ensure we had enough self-generated electricity to meet the need? What other items did we have, or plan to get, that would also need power? It’s always a good plan to plan for more capacity than what you think you will need.
The only other key items in our cache needing power (either directly or by charging its batteries) were: our Voice Alert Intruder Warning Station and sensors, several Night Vision scopes, the Marine Band transceiver on our boat, and a bunch of flashlights. Only the Voice Alert was added to our “needs power” list for the purpose of calculating total electrical load requirements.
I mentioned a Marine Band Transceiver in the previous paragraph. Let me digress for a moment to discuss where it might fit into the scheme of things. Since Marine Band frequencies are different from FRS, CB, and standard SW Band and since folks in a survival mode would likely be using those more common devices to communicate; using a marine band radio to connect with your friends provides a small measure of “secure communications”.
At least it would be somewhat more secure than other methods of communicating over the airwaves. People living in landlocked areas don’t tend to think about Marine Radios and would probably not be monitoring those frequencies. Back to the main topic.
Starting with the assumption that there would be no grid electricity or phone system operative, our communication devices would need to be powered by whatever electricity we could generate. We’ve got a large gasoline generator that will provide a lot of juice, enough to run our home if needed.
But even with rationing our supply of gasoline it will only last so long. Scrounging for more fuel during the first few months of chaos might prove to be unproductive, as well as a very risky chore.
Wind or water power is not an option where we live so that’s out of the equation. Solar power is an obvious choice. A bank of solar cells, charging a bank of batteries, powering an inverter to produce AC power, is feasible; but I have some reservations regarding this type of arrangement.
First is the number of solar cells required to produce adequate charging current and second is the number of batteries that would be needed.
Those two issues, plus our northern locale and the reduced daylight hours during the 6 months of our winter cycle (at Winter Solstice we have about 8 hours of daylight) made me reluctant to bite the bullet and put our funds into a large, complex solar power supply.
The ratio of expense versus return just didn’t seem to make a large solar-powered system worthwhile. I wanted a system with as few components as possible. The more components there are within any system, the greater the likelihood one will fail; thus rendering the system inoperative.
Considering all of my negative concerns, solar power still seemed to be the answer. I decided to compromise; I’d use solar power on a smaller scale to power our communications system. With a working solar power supply, we could then hold back on using our generator. This has a positive impact since the generator is noisy and would attract attention. A solar charger is silent.
System Design Criteria: I searched through commercial products to see what was available but couldn’t find anyone device that had the features I was looking for.
Nowhere was there a solar-powered, battery based, a multi-voltage power supply that would suit my wants and needs.
So, I decided to design my own. I wanted to follow the time-proven “KISS” philosophy of design ………….. Keep It Simple Stupid! The result is a system that is based on two main components: A Portable Solar Battery Charger and a Power Panel.
- The Solar Charger needed to be portable so I could easily move it around the property to wherever the sunlight was strongest.
- The Solar Charger would need to be able to recharge a slightly discharged Deep Cycle 12 vdc RV battery within 8 – 10 hours.
- The portable Solar Charger should have an onboard 120vac-12vdc charger to provide one more way to charge a battery.
- The battery used would need to have enough capacity to power the equipment for at least 12 hours out of a 24-hour cycle.
- Two batteries would be used initially, although more can be added if desired.
- Each day (of the use cycle) the batteries would be swapped. The freshly charged battery would come into the house to be connected to the power panel. It would replace the battery that had been used the previous day & night. The slightly discharged battery would then be rolled outside (on the Solar Charger) for recharging.
- The Power Panel would be designed so as to provide easy access to facilitate battery and device connections.
- The Power Panel would supply 12, 9, 6, 3, and 1.5 vdc as well as 120vac at amperage levels required by the devices (Radio, CB Station, etc.).
- 120VAC would be supplied to the Power Panel by three sources: Normal Grid connection, Generator, and an onboard 12vdc to 120vac Inverter.
- All of these DC voltages, plus the 120 VAC, would be readily accessible on the face of the Panel. A connection would be by the use of common connectors, alligator clips, terminal strips and the like.
The Portable Solar Charger and the Power Panel would comprise a very flexible electrical supply system. As long as we had grid power or were using our generator the Solar Charger and the Power Panel would remain in standby mode.
Electrical Sizing: Once I had decided on the general details for the charging station and power panel, I set about figuring which specific communication devices I wanted to purchase. This was necessary so that I would know what the estimated total power requirements were for each device.
That way I could ensure my system would be adequate for the load. As I said earlier, I wanted to be able to have a way to communicate via CB, be able to listen to what was being broadcast locally on emergency channels, receive worldwide broadcasts, and play CD’s or cassettes (yes I still have boxes of them).
After shopping around, I selected a CB base station by Galaxy, a world/all band receiver from Grundig, a Uniden300 Channel Broad Band Base Station Emergency Frequency Scanner, and a nice little Sony AM/FM/Cassette/CD Radio & Player. Another electrical device that would be connected to the Power Panel is our Voice Alert System base station.
I obtained the amperage requirement specifications for all of these devices. Both idle and operational mode values were figured into the equation. The total wattage needed would be my guide in choosing an appropriately sized battery as well as other assembly components.
The Voice Alert Perimeter Defense system (which would be on almost all of the time especially at night) draws less than a ½ amp/hour. If the CB Base Station is turned on it will draw less than ½ amp/hour in the Receive-Only mode, and less than 1 amp when transmitting.
The World Band Receiver uses less than ¾ amps/hour. The scanner uses less than ¾ amps and the Cassette/Cd player uses ½ amp/hour at a normal sound level. If the CB Transmitter or the Inverter was in use the current draw would be greater: meaning that the battery would need longer to recharge.
And of course, the louder the audio setting the more current these units will draw. If all of them were turned on at the same time the total current draw is still well within the arbitrary 5 amp limit.
After a search, I selected a Deep Cycle RV battery made by Interstate (SRM-27) that was rated to provide 12vdc @ 5 amps 19 hours. It would be a rare occurrence when all of these devices were in use at the same time so in all likelihood, the battery would actually be put to use for less than 12 hours a day.
This battery was perfect and would work well to satisfy my initial target value of 5 amps. The Interstate battery would work just fine!
Portable Solar Charger Design: Having settled on the major components, and the overall design of the portable solar charger and power panel, I began the actual layout design work. I settled on using a common hand truck purchased at a local retailer as the base on which to design the portable charger.
The hand truck was large enough to accommodate all of the components. It would work well as the batteries are heavy and unwieldy to carry around. An additional plus is that the entire charging station can be rolled into the house for security and to facilitate the battery exchange.
The Solar Power Charging Station is essentially a 20-watt solar panel connected to an SP Charge Controller. The solar panel is mounted on the hand truck so it can be pivoted at the top on a vertical plane. This allows it to be angled so as to best capture the rays of the sun, yet present a slim profile when not in use.
I added a special locking hinge that allows the angle to be easily set. The Solar Panel Battery Charge Controller moderates the output of the panel and keeps the battery from sulfating over time. A very small meter was added so I could monitor the voltage of the battery as an indicator of its charge level. T
o give added flexibility to the unit I added a small 120vac charging unit. A heavy plastic battery box is mounted on the foot of the dolly. Each of the electronic devices was mounted to the hand truck so as to be able to easily remove them. This was done so the individual components could be stored in my grounded Faraday Shield cabinet ………… just in case!
Power Panel Design
The Power Panel is simply a fixed panel that has a variety of quick connect terminals and cables that can be selected and connected with ease. It has two inputs: 12vdc (using battery clips) from the batteries currently in use) and 120vac (using a standard extension cord type connector plugged into a wall outlet). The 120vac is used when our generator is running and supplies 12vdc by powering a standard charger.
The 12vdc to 120 vac inverter is also mounted to the panel. I added a switch so I can choose between Generator/Grid 120vac or Inverter 120vac). The inverter I chose is a Power Bright PW1100. It will provide 1100 watts and draw roughly 9+ amps when used at its max capacity.
It is not a true sine wave inverter but then again I don’t need one. I do not foresee having to use the inverter all that much, but it’s nice to have it wired in and available if needed.
There are no indicator lamps as they just add to the load on the supply. The output connections are all switched and labeled to reduce confusion. I did add a 12vdc switched light (low current LED) to illuminate the panel and immediate surrounding area.
The best radios in the world are worthless unless connected to a good antenna. To complete my communications system I bought a Solarcon I-MAX 2000 24’ CB/HAM Base Station vertical antenna. I constructed a 40’ long-wire receive only antenna.
Both are mounted on the roof peak of my home and feed into my office. The roof peak is approximately 40’ high so the antennas are nicely elevated. These antennas extend the operating range of the CB and significantly improve the reception of any receiver.
to be on the safe side I also added a lightning arrestor. There are other antennas available but I believe that the ones I have chosen are a good compromise.
Major components of my Solar Charger, Power Panel, and the Communication Devices:
•CB Radio, Galaxy DX-2547 AM/SSB CB Base Station
•Eaton (Grundig) 750 Satellite AM/FM Stereo/Shortwave/Aircraft band Radio
•Sony CFDS05 CD/Cassette/AM/FM Radio
•Uniden 800 MHZ 300 Channel Base or Mobile Scanner (BC355N)
•Cobra HHRoadTrip Hand Held CB Radio (x4)
•Maybe: Baofeng UV5RA Ham Two Way Radio 136-174/400-480 MHz Dual-Band Transceiver
•Instapark 20W High-Efficiency Mono-crystalline Solar Panel
•HQRP Solar Panel Controller 10 AMP @ 150 Watt
•Power Bright P-1100 12vdc-120vac Inverter
•Solarcon I-MAX 2000 24’ CB/HAM Base Station Antenna
•Battery Tender 021-0156 Battery Tender Plus 12V Battery Charger True Gel Cell Model (x2)
•Mini Blue Digital Panel Voltmeter 4.5 – 30v for 9, 12, and 24 vdc (x2)
•Adjustable Drafting Table Hardware, lift up ratchet support, sold By Rockler
•Wineguard DS-3000 “J” Pipe support for antennas (x2)
•Coaxial Lightning Antenna Surge Protector LP350
•Hand Truck with air-filled tires, $60 @ Home Depot
•Misc. screws, bolts, wire, coaxial cables, etc.
•Custom mounting plate for Charge Controller, etc.
As of this writing, the Portable Solar Charger has been completed and works as designed. A “maintenance level” charger is kept on both batteries to ensure they are always fully charged. Assembly of the Power Panel is in progress and I expect it to be completed in the near future.
Below you’ll find several photos on the Portable Solar Charger and a very basic schematic for the electrical connections. They should give you an idea of how I put it together. It’s not necessary to be an electrical engineer to assemble a system like this.
All of it is basically a “plug and go” type arrangement with common components readily available off the shelf. You too can put one together and tailor it to your own needs.
Define what you want to do, what type of devices it’ll take to do it, then make a parts & components list. Be sure all of the components you’re going to put together are compatible and will give you the power you need.
Almost everything I used is available online or at your local hardware store. I did have a local metal shop fabricate an aluminum square “C” shaped plate for mounting the SP Controller and small battery charger. The purpose of the “C” shape, beyond providing a mounting plate, is to shield those two components from the weather.