Intro: Ammo Can Solar Power Supply
For this project, I'd like to show you how to build a portable solar power supply in an ammo can!
This is a great project to learn about the basics of electronics, batteries, and renewable energy. The finished project can charge a phone or tablet, light up a camp-site, and provide for whatever other small electric needs you have.
This is ideal for emergencies, camping, or any off-the-grid getaway.
Whether you call it a solar generator, a camping go-box, or anything else, you'll love having an Ammo Can Solar Power Supply!
For a quick video overview of the project, please see:
For the full-length, step-by-step, instructional video, please watch at:
Step 1: Materials and Tools
This project is essentially a battery inside a sturdy box with a handle. I choose an 50 caliber plastic ammo can, as I've found them to be very handy as tool boxes and storage containers. Ammo cans stack nicely, carry easily, and have a weathertight gasket seal.
In the past, many of my projects made use of "Unique Parts" (such as bulletproof glass pulled out of a dumpster!) In this case, I wanted to made use of as many "off-the-shelf" parts as possible. For one thing, it makes it very easy for OTHER people to also make their version of the same project.
In this case, I happened to purchase most of the components from a major online retailer. If you'd like to do the same, I've provided links to the items I used. I've also added approximate prices for those materials at the time of this writing.
For this project, we will need:
Ammo Can, 50 cal.
I really like the MTM brand. Nice boxes, made in the U.S.A. Available in multiple colors. Black and green are both classic, but you might want high visibility orange if you intend to use this as emergency equipment. http://amzn.to/2FI8lFw
Sealed Lead Acid Battery, 15AH capacity. I specifically chose a particular physical size, as it fits perfectly inside the MTM Ammo can. It's also a relatively small battery, which keeps the project weight to right around only ten pounds. I used a "Mighty Max" brand battery. http://amzn.to/2FBmroN
20A Solar Charge Controller I found a nice one which has some good safety features, low-voltage disconnect, and also includes a pair of USB ports built in. http://amzn.to/2FAJyjo
Four In One Socket Panel This is a device typically sold for trucks to add a 12V cigarette lighter outlet, USB ports, a voltmeter, and a switch to turn it all on and off. They are available in several shapes sizes and colors. http://amzn.to/2FHxCj4
Banana Jacks These are used as universal electrical inputs and outputs on the project. This project uses two pairs, but since I knew I'm be using more in the future, I bought a box of 10. http://amzn.to/2FMDK9I
12 AWG stranded wire in both black and red (From local hardware store)
Crimp on electrical terminals, spade and 1/4" ring terminal
Silicone adhesive or hot glue
Industrial type hook and loop fastener (Velcro) http://amzn.to/2FMDK9I
Wire Nuts or Wago (Brand) Lever Lock Nuts. http://amzn.to/2FBj15k
Fuse Holder and Fuse. http://amzn.to/2FMLmJp
6-32 and 8-32 nuts, bolts, and washers
The project also features "accessory items" that simply plug in to the Solar Ammo Can to make it as useful as possible. To start with, we will want to be able to charge the battery.
Solar Panel - I already happened to own a solar panel perfect for this project, a 15 watt PV Solar panel. Any 12V nominal solar panel of about 10 to 20 watts is perfect for this project. Here's one which looks affordable, and it about the right size and style for the project. http://amzn.to/2DlkpHw
DC Power Adapter (Wall Charger) Any DC wall power adapter of higher than 12V (13.2, 14.4, 18) and one amp will work fine. I already had a 18V 1.3A power adapter handy. Here's a similar adapter. http://amzn.to/2FMUrBS
The other items I packed into the ammo can were for lighting and AC power.
USB Gooseneck Light These small USB lights work great. They are very simple and durable. Fantastic for camping. http://amzn.to/2GhvQTy
100 Watt AC Power Inverter. This device converts DC power to AC power so that you can run typical household devices from a battery. A 100 watt version is very compact and inexpensive. I already had one, which I used for this project. Here is a similar version. http://amzn.to/2FBjGDQ
For this project, we'll need some pretty straight-forward shop and electric tools:
Tape measure / Ruler
Drill and drill bits (alternatively, access to a laser cutter)
Nut-drivers or sockets to fit 6-32 and 8-32 hardware
Optional: Access to a CNC Vinyl-Cutter to make a graphic.
Now that we have our tools and materials, let's get to work!
Step 2: Laying Out Components
I set the battery inside the ammo can, and arranged it approximately in the middle. This helps with balance, so the finished project doesn't feel off-center when you pick it up.
There is empty space on both sides of the battery. On the one side, that space will be taken up by the wiring from the back of the various electrical connections. The other side will be reserved as storage space so that we can include lights and the power inverter in the project.
All the switches, outlets, and connections will be INSIDE the ammo can. The ammo can is already designed to be weather-proof and includes an o-ring or gasket. Some people have designed similar projects where they drill holes through the sides and top of the ammo can. To me, it seems a shame to put holes into something that's already designed to be weather-proof!
Instead, we will design an internal faceplate which will go over the top of the battery and mount all the components together.
The area inside the ammo can, covering the battery and the one open side, comes to approximately 6 inches by 8 inches. I drew that rectangle out onto a piece of paper, and then started to arrange my main components. I wanted to include the Solar Charge Controller, the 4-in-1 Socket Panel, and two pairs of banana jacks on this panel. I arranged the components so that the Solar Charge Controller would be directly over the top of the battery, and the other components were to the side of it.
With the components in place, I could trace them and their mounting holes.
After I did that, I did the same on a piece of cardboard. Cardboard is nice because it's inexpensive and quick and easy to work with. It makes a good temporary mock-up. (I call this CAD - Cardboard Aided Design.)
I cut the holes in the cardboard and temporarily installed the components to make sure that they would lay out well and sit inside the box over the battery as I would expect.
On a typical home workshop project, this is the point where I would lay my paper template over a piece of wood or plastic and drill the holes and cut out the shape. In this case, I realized that other people might want to duplicate my project, and that having a DIGITAL version of my layout could be useful.
I took the individual components and placed them in a computer scanner. I scanned in the components, and then brought them in to Vector editing software. (I happened to use Adobe Illustrator, but any vector software will work.)
Inside the vector software, I could draw the shape of my faceplate and precisely locate the holes that would be needed to mount the components.
Step 3: Cutting the Panel
If you just have access to common shop tools, lay your paper template over a thin piece of wood, metal, or plastic and tape or glue it down in place. (Thin plastic cutting boards are commonly used as source materials for projects like this.)
Next, drill holes as needed for mounting down the components. (I mostly used 3/16ths inch holes)
The holes for the cigarette plug style connections in the 4-in-1 Socket will require a 1&1/8th inch spade drill bit, or better yet, the same size Forstner bit.
On the other hand, if you have access to a laser-cutter, load the vector file you created into the laser-cutter computer. Make sure to adjust settings as needed for whichever material you are using. It's always a good idea to make a test cut on some inexpensive disposable material.
I added some text I wanted engraved with the laser-cutter, but forgot to set it to a lower power than the cut lines. Instead of engraving, the lettering was cut right through! Oops! Good thing that was just on a test piece of cardboard. After correcting the power setting, we cut a faceplate panel from a piece of 1/8th inch thick plywood.
It looked very nice, with clean cut lines, and easy to read engraving.
Included in this step is an Adobe Illustrator file and a DXF file, if you would like to laser-cut this same component.
A big thank you to our friends at Brown Dog Gadgets for their assistance with laser-cutting!
Step 4: Assembly
Assembly onto the faceplate is relatively straight forward.
Use the 8-32 hardware to mount the 4-in-1 Panel. Next, push the individual components (switch, USB plugs, etc) through the large holes and then secure them by rotating the rings on the back.
The banana jacks are pushed into the plate and then a backer goes on, which is held in place by washers and a nut.
I recommend NOT mounting down the the Solar Charge Controller right away. Because the wiring has to come up through the faceplate to get to the Solar Charge Controller, it's difficult to get the wires to the screw down terminals. It's easier to wire the Solar Charge Controller, and THEN mount it down to the faceplate.
At this point, you now have the components assembled to the faceplate. Flip the faceplate over and wire up the project.
Step 5: Wiring
The Solar Charge Controller is rated for up to 20 amps of current. As such, we want to use wire and connectors rated for 20A as well. That means using 12 AWG wire. Crimp on terminals that work with 12 gauge are usually color-coded yellow.
Our 15AH lead-acid battery has 1/4" spade terminals on it, so we will crimp on a female spade terminal onto the end of the fuse holder. The other end of the fuse holder is stripped and inserted in to the Battery + connection on the Solar Charge Controller. We will use a black wire with a female spade to connect the battery's negative terminal to the screw down terminal on the Solar Charge Controller marked Battery -.
For the banana jack marked "Solar IN" we will crimp on a ring terminal onto the end of a wire. Cut that wire to length to reach the Solar Charge Controller. A red wire will go from the red banana jack to the SCC (Solar Charge Controller) screw down terminal marked SOLAR IN +. Likewise, a black wire with a ring terminal to the SOLAR IN -.
Wiring the loads is a little more complicated. Besides the 4-in-1 Socket panel, we also have the additional banana jack as a secondary 12V output. Each electrical device needs to connect their positive with a red wire to the LOAD + on the SCC and every negative has to go to the LOAD -.
Since we have multiple connections, but only one screw each on the Solar Charge Controller, we will need to combine wires by twisting them together with a wire nut. Alternatively, I recently found a connector made by a company called WAGO. They have a Lever-Lock Nut. This device allows multiple wires to combine together, sort of like a mini bus bar. Each conductor locks in place by a spring-loaded lever. These lever lock nuts are rated for up to 20 amps, are reusable, and make it easy to add or remove wires.
I crimped a female spade connector onto a black wire for all the load negatives. The opposite ends were stripped and then combined together in a Wago nut. That nut also connected to the LOAD - on the charge controller.
The positive side was slightly more complicated. I wanted the banana jack always on, but the items in the 4-in-1 Socket Panel to be switched on and off. To accomplish that, I ran the positve red wire from the solar charge controller LOAD + to a ring terminal on the positive of the banana jack AND to the middle conductor on the switch of the 4-in-1.
Next, I made red wires with spade terminals to connect to the positives of the remaining connector (switched output) on the switch and the other items of the 4-in-1 Socket Panel.
That provides power always on to the Banana Jack, and power to the 4-in-1 only when the switch is on.
Once everything is wired, the Battery + and - wires can be plugged into the battery, and the system can be tested out.
Step 6: Battery and Panel Mounting
One of the goals of the project was to not drill or cut holes in the ammo can.
So, then how do we mount the components inside the ammo can? What keeps them from shaking loose and sliding around?
The battery really already fit very snug. To secure it, I placed a few dabs of silicon glue (caulk) in both the bottom and the sides of the ammo can. I then placed the battery back down in the ammo can and let the glue dry.
The faceplate with all the electrical components mounts right over the top of the battery. I held it in place with industrial strength Velcro brand hook and loop fastener. To allow for the space taken up by the battery terminals on the top of the battery, I added a small wood spacer, glued that directly to the top of the battery, and velcro'd the faceplate on there.
Using Velcro securely holds the faceplate, while still allowing for easy removal to access the wiring. You would need to do this to replace the main fuse, for example. Also, if the project is going to be put in storage for a while, you would want to completely disconnect the battery. Always store batteries charged and NEVER with anything attached, including a battery charger which is not actively charging.
As a finishing touch, I created a graphic on my vinyl-cutter using a stencil font and applied it to the ammo can.
Step 7: Solar Charging
This system is designed to be charged by a solar panel
What size solar panel do we need, and how long will it take to charge?
A "12V" solar panel is actually one which is designed to charge a 12V battery. To do so, it needs to produce voltage HIGHER than that of the battery. Common solar panels used to charge 12V batteries are often about 18V
Every solar panel will have a sticker on the back listing its maximum voltage and maximum current. The one I have is rated at about 18 volts and 1 amp max current.
The battery is rated at 15AH (am-hours.) If it was completely depleted and I had a 1 amp solar panel, it would take 15 hours of full sunlight to recharge. However, we never want to completely drain a battery. It's pretty common practice to discharge a 12V lead-acid battery to no more than HALF.
In that case, we would need to replace 7 or 8 AH and if we were using a solar panel producing 1A, it would take 7 or 8 hours. I'm intending to primarily use the Solar Ammo Can while out camping during the summer - the time of year when the days are extra long, and the battery would get plenty of charge.
For this project, a solar panel with a 1 amp output will be sufficient, and a 2 amp output would be even better.
Here's a video review of a small solar panel appropriate for this project: https://tinyurl.com/ybp3qyz3
So, how do we charge the battery at night or in cloudy weather?
You will notice that there is NO AC input on the project. To charge from AC grid power, we will still use the SOLAR IN connection.
A DC power supply converts the AC to DC and the Solar Charge Controller will properly control the charging of the battery. The DC Power Supply (wall wort!) simply needs to provide voltage higher than that of the battery. There are some power supplies which specifically output 13.2V or 14.4 volts specifically for 12V charging. Anything in that range on up to the maximum the Solar Charge Controller is rated for will work fine. (A laptop power supply would work great!)
I'm using an 18V 1.3A DC power supply for grid-charging the Solar Ammo Can.
Step 8: Using the Solar Ammo Can
In use, the Solar Ammo Can is super-handy!
I open the lid and have the small gooseneck LED light ready in the USB.
The 12V DC LED bulb is extremely bright. The cord on it is long enough to throw the bulb up over a tree-branch. The hanging bulb will light up a whole camp site!
The AC Power Inverter works great too. I don't need it that often, but it's nice to have. It works well with long strings of LED lights which are designed to work on AC - they are low current, but still require AC, so they are a nice match with a small inverter. I have a string of AC LED lights on my back porch. Each bulb is only one watt, and there's a dozen bulbs in the string. Total power is 12 watts. The ammo can can power my back porch in a blackout. Alternatively, this style of lights is great for lighting up an area at a camp-ground, or even for interior lighting in a blackout!
The USB jacks work great for charging phones and tablets. Keep in mind that some USB jacks are only good for 1 amp or less. All the USB connections on this project are at least 2.1A - so tablets and other power hungry devices can charge at full speed!
Having all the accessories pack INSIDE the box works really well. If they didn't I'm sure they'd all get lost!
The only thing which DOESN'T fit inside the ammo can is the solar panel itself. I have found a folding solar panel which could fit inside a 50 cal. ammo can and I have some ideas for a future version where even the solar panel fits inside!
Lastly, there's more than one way to make a project like this. People have used tool-boxes, built custom wood cases, used very large batteries, added wheels, and have done almost every other variation you can think of.
For me, I wanted something portable, which looked nice, and could power communications and lighting. I think it's accomplished that goal just fine!
Now, it's time for YOU to make one! Show us what you come up with!
Step 9: Disconnecting When Not in Use
One thing that can be somewhat strange about battery chargers is that they can DRAIN the battery!
Many battery chargers, if left connected to the battery, but NOT powered up, can drain a battery. That can include a solar charge controller like the one used in this project. For example, the charge controller has a display. Simply powering display that takes energy from the battery.
When NOT using the Solar Ammo Can, you can simply pull the main 12+ positive connection from the battery. Alternatively, you can pull the 12V fuse.
If you would prefer, you can also wire the project slightly different so that the switch in the Quad-Socket acts as a disconnect switch between the battery and the solar charge controller. Remember to flip the switch to ON when trying to CHARGE the battery as well!
Please see the image for the alternate wiring diagram.