This is an entry in our current non-fiction writing contest By DanW
This article covers the second half of my Portable Solar Battery Charger & Power Distribution Panel project. This is a detailed description of how to build a Multi-Voltage DC and (Inverter generated) AC Power Distribution Panel complete with a parts list, component functional descriptions, schematic, and photos. Although I tried to be concise, it still turned out to be rather lengthy! After conferring with MD, we was decided it would be best to publish this as a 4 part series. Part 1, 2, and 3 will include the design details, schematic, and several photos of the Power Panel. Part 4 will be the Construction Notes. So, thanks in advance for your patience ………. Hope you like my efforts!
A note of caution: When working with anything electrical you should always pay heed and follow all safety procedures to prevent harm to yourself or others. I suggest you do not attempt to build and/or use one of these units unless you have a good working knowledge of basic electricity.
This Power Distribution Panel turned out to be a bit more expensive than I expected. But, flexibility comes with a price tag. Before deciding to build this project I did some research to see what was already available. I found several bench power supply units that produced a range of voltages …….. one voltage at a time ……. and of course they all required 120 vac input power. They were also in the $600 – $800+ price range and not designed with the versatility of this little Power Panel. You may find that your version of this project is less expensive ……….. It could certainly be built for less. But, if you scrimp on your design now it will be very difficult, if not impossible, for you to add to its features after the SHTF. I know it will power the devices I currently have, but what if I had to replace one of them? Even if I’m able to find a similar device …….. would a less complete Power Panel be able to meet its power requirements?
Hopefully I’ve given you all of the information you’ll need, without getting too technical, so you can make one of these for yourself. The schematic, layout design, and photos should help to clarify all of this.
My goal was to design a compact, relatively portable power panel that will provide multiple voltages at the same time, generated by multiple electrical sources utilizing flexible connectivity for multiple load devices. Whew! That’s a mouthful ………. but it does kind of say it all in one sentence.
This Power Distribution Panel is designed to be used with a 12 vdc deep cycle battery as the primary power source. In my case that’ll be a battery charged using my Portable Solar Charger. I’ve made the design as flexible as possible for my own needs; but, since not everyone will need or want something with all the features I’ve put together, this design lends itself to be inherently flexible. You can easily select which portions of the circuitry might suit your needs and build yours accordingly.
My earlier post http://www.thesurvivalistblog.net/power-for-communications-defense-and-entertainment/ outlines how I designed and built a hand-truck based Portable Solar Charger. The design process for that unit was predicated on producing enough solar generated electricity to be able to charge a deep cycle battery. I took into consideration the need for a battery of sufficient capacity to supply 12 vdc @ 5 amps/hour output for at least 18 hours. I arbitrarily selected 5 amps as the max total current draw (Ampere Load) to be placed on the battery based on the power requirements of my load devices. It should be a rare instance if all of the devices were being used at the same time. So, the factors determining the battery’s discharge rate was the total size of the ampere load (CB Base Station, Scanner, Radio, etc.) and the length of time the battery would need to be able to reliably supply that load (18 hours @5 amps).
Having resolved those issues, it was now time to address the Power Panel design and assembly. I needed to take into consideration the various voltages required to power my equipment, the layout of the unit so as to provide for quick and easy connections, and the overall physical size and dimensions of the Power Panel. An additional factor was the need for this Power Panel to be somewhat portable. By “portable” I mean being able to set it up in a variety of locations if desired. My radios, CB base station, scanners, and home perimeter defense system base unit, etc. all can be powered by 120 vac, 12, 9, or 6 vdc. Therefore, these are the voltages to be supplied by the Power Panel. Armed with that list, plus a rough idea of how I wanted to physically connect the power cords from each device to my panel, I searched the internet for quick-connect power strips. I wanted to find this component first as it would, to a great extent, determine the physical size of the panel as well as the final layout. After a lot of online browsing I found the exact thing I was looking for ……… a power distribution unit made by Tenma.
The Tenma Units:
Manufactured by Tenma, these DC Power Distribution Multiple Outlet Panels are readily available from a variety of retailers. I purchased three from MCM Electronics http://www.mcmelectronics.com/ as they had the best unit price plus free shipping. Once wired, each of these Multiple Power Output units would offer a different voltage: 12, 9, and 6 vdc respectively. Referring to the schematic, you’ll see that the three Tenma units get their power from the 12 vdc buss. These units are divided into two sections: switched and un-switched. The un-switched pair (each with a 35 amp fuse) is rated at 35 amps total while the switched set of 6 pairs is rated at 15 amps total with one 15 amp fuse. The only thing I did not like was the rather inconvenient location of the fuses: all three fuses are internal and not easily accessible. A work-around solution to this issue is the addition of another fuse on each Tenma unit. A panel mount style fuse holder with twist off cap holding a 10 amp AGC fuse will protect the switched DC outputs. Theoretically, this 10 amp fuse will fail before the internal 15 amp fuse. I drilled a hole in the right side of each Tenma unit to mount the new panel fuse holder. Once the fuse holder is installed it must be wired into the circuit. (Since the fuse is held in the fuse holder by spring action you should use a flexible type stranded wire rather than solid copper for these new connections.) To do this you will need to cut the existing solid copper wire from the small internal circuit board to the On/Off Switch. Connect each end of this cut wire to the terminals on the new fuse holder and insert a fuse. The fuse holders on the 9 and 6 vdc Tenma units are not actually needed since these two units are protected with front panel mounted 5 amp fuses on the positive output side of the respective voltage reducers. However, I went ahead and installed fuse holders in these units for the simple reason of being able to use the 9 or 6 vdc Tenma units as replacements for the 12 vdc unit if it was ever needed.
Each Tenma unit comes with two Ammeters: One for the un-switched outputs and a second one for the switched outputs. The output connections are banana type posts, used in pairs (+ and -) where your devices (radio, scanner, etc.) can be quickly and easily connected. These “banana” type posts can also be unscrewed to expose a hole that will accommodate a bare wire. Once the wire is in place you tighten the screw part down firmly. This option eliminates the need to purchase the banana type plugs if you chose. There is also black Banana plug jack labeled “Ground” on each Tenma unit. This ground terminal is connected to the Tenma case only and is isolated from the positive and negative Tenma DC outputs. If you connect this ground terminal to the AC ground then the metal front panel will be grounded. As I comment below, this may cause problems so I suggest you leave this ground terminal unused.
Voltage Reducers - Note also that there are two voltage reducers in use: 12vdc to 9 vdc and 12vdc to 6 vdc (see the parts list). I found these Voltage Reducers online at http://www.powerstream.com . Rated at 5 amps, they are each protected with a 5 amp fuse placed in the 12 vdc positive line feeding each voltage reducer. Higher amperage and different values are also available.
Basic Power Panel Box Construction:
I addressed my desire to keep the AC and DC circuits separate by using a combination of metal and wood for my front panel design. The metal section will be DC circuits while the wooden section has primarily AC circuits. I did this for two reasons:
- To provide electrical isolation between the 12 vdc and 120 vac components. I don’t know the electrical integrity of the various components (primarily the voltage reducers) and it is possible that mixing in an AC ground with the DC components may cause interference or damage to some of these devices. Keeping them somewhat insulated from each other reduces that possibility.
- From an assembly standpoint it is easier to mount the various switches, meters, and other components to the thinner metal panel than it would be on a much thicker wooden panel. My Construction Notes deal with issues of mounting components on the thicker wooden panel.
Your enclosure will be defined by your needs and imagination. The size of the box frame and metal mounting plate will depend on your particular layout, number of components to be mounted, etc. I decided to use a piece of light gauge aluminum for the front panel component mounting plate. This plate slides into a slot cut into the inside of the wood frame and is held in place when the top piece of the box is attached with screws. I used a wooden section (assembled with the box frame) for mounting the 10 Socket 120 vac Power Strip and associated switch, the 120 vac Meter, and the Inverter switch and fuse. Red oak was used for the box as it is stable and strong. Pre-fitting showed me that I needed to use a piece of 2” x 8” (3/4” x 7 ½”) cut down to a width of 6 ½” for the bottom of the box frame. This was done so that the Inverter would fit properly. I cut a slot in the back bottom of the wooden front panel section where one side of the Inverter mounting plate will fit. The finished dimensions of the box are 24 3/8” x 22”. I used Philips head machine screws to assemble everything so it could all be taken apart easily with a manual screwdriver.
The layout for drilling and cutting rectangles in the metal and wood front panels is a critical aspect of producing a final product that is organized and neat. I used a piece of light weight poster board to make a layout template (using the actual components) which I transferred to the front panels. Then it was a simple matter of making the cuts and drilling the holes using step drills (See Optional Parts List). It’s much better to make your layout mistakes on paper ……. rather than on your actual panels.
To Be Continued: Part 2 will be published soon and continues with more information on design details and assembly of this Power Distribution Panel. A detailed parts list and component functional description is include in Part 3 with Construction notes in Part 4.
Prizes for this round (ends May 24 2014) in our non fiction writing contest include…
- First place winner will receive – A $150 gift certificate for Hornady Ammo courtesy of LuckyGunner, a Wonder Junior Deluxe grain mill courtesy of Kitchen Neads, a one year subscription to the Personal VPN service courtesy of unspyable and Three Survival Seed Vaults courtesy of LPC Survival.
- Second place winner will receive – Brand New, Sealed Case of Military MREs (Meal, Ready-To-Eat) a $119 value courtesy of Campingsurvival.com and a Survival Puck courtesy of Innovation Industries.
- Third place winner will receive – a copy of my book ”31 Days to Survival: A Complete Plan for Emergency Preparedness“ and “Dirt Cheap Survival Retreat” courtesy of TheSurvivalistBlog.net a copy of “The Survival Medicine Handbook” courtesy of www.doomandbloom.net and a copy Herbal Antivirals and Herbal Antibiotics .