Homemade solar panel charger. The key is to skip the inverter and power directly…

How to Build a Solar Charging Station Anywhere

One of the most amazing innovations in the last five years has not been a new invention as the perfection of existing technology. Solar panels, which were once the territory of only the very rich and very environmentally dedicated, have gotten smaller, more efficient, and more affordable, and you don’t even need to mount them on your roof. Many people still think that solar is in the realm of “Go Big or Go Home,” but we’re here to tell you that times have changed.

Building a Solar Charging Station

While you can start your adventures into solar power generation with a full rooftop-mounted and grid-connected installation, you can actually learn about solar and build yourself a disaster-ready power generation and charging station for less than 500 and a little elbow grease. With this simple and easy to connect contraption, you’ll be able to generate enough power to slowly charge an electric vehicle or keep several mobile devices powered for as long as the equipment lasts.

Building a solar charging station is surprisingly simple because the components are now very efficient. All you need is power generation, power conversion, power storage, and the cables in between. All the parts can be bought on Amazon from various manufacturers, so compare and amperage until you find the right combination for your budget and power generation needs.

• Portable Solar Panels
• You don’t need a professional to affix some weather-resistant solar panels to a sunny spot and draw power. You don’t even need a stable location. Portable solar panels can be mounted, unmounted, and moved at any time, wherever you happen to need solar power.
• Solar Cables – One Red, One Black
• These will connect the solar panels (which have matching leads) to the solar controller and inverter, which will regulate the energy from the solar panels and make them useful.
• Solar Controller
• The solar controller device is part of what makes solar power so much more accessible than it used to be. It’s essentially a specialized charge controller with a useful info display screen.
• Inverter
• The inverter is what turns the DC solar energy into AC device and appliance energy. They usually have at least one power socket and often have USB ports as well. Some inverters come with their own batteries.
• Batteries
• A deep supply of battery storage ensures that you don’t waste solar power and have plenty to last you through the night and on rainy days.
• Battery Cables – One Red, One Black Per Battery
• These will connect the batteries and the solar controller, allowing the controller to balance voltage between, serve power out of them, and prevent them from over-draining.

You can build your solar charging station on anything you want. For an electric car charge stop, you can put the panels on top of a carport and stow the rest of the equipment safely in a cabinet within. You can add them to a camp cabin or tent to power basic equipment like a camp stove or radio. With flexible panels, you can even stick them securely but temporarily to the top of your car, truck, or RV with 3-5lbs Command strips for convenient mobile device charging on road trips. The Command strips don’t damage the paint when removed, so you can experiment freely without having to make even semi-permanent alterations. Choose what you’ll mount the solar panels on and how you’ll protect the electrical equipment before getting started.

Step 1: Mount the Solar Panels

For a semi-permanent structural mount like on a shed or carport, use a metal frame and bolts to attach the solar panels to the roof of your structure. Make sure to use the right brackets and screws based on the type of roof you’re working with. Tents should rely on either foldable solar panels or those with holes so they can be tied to the top or sides. A car either permanently mounts them with a frame or temporarily mounts them with safe sticky strips.

Step 2: Emplace the Batteries

The batteries need to be in a safe, dry, moderately temperature-controlled, and stable position. Anywhere indoors is usually fine, but they need to be carefully secured in a vehicle and probably carried in a sealed box for camping.

Step 3: Place the Solar Controller

You’ll want the solar controller somewhere safe but easy to read, as it will tell you how much energy is being generated, how much is being drained, and approximately how full your collection of batteries is. Make sure it’s accessible before wiring and arrange your connections around where the solar controller needs to be.

Step 4: Connect Everything

Connect your solar panels and the solar controller with the solar power cables using parallel or serial wiring based on your amperage and voltage needs, then do the same for the batteries. If you need a converter from the batteries to the power ports you plan to use, connect this to the solar controller and its own cables.

How a Solar Panel Works

Inside a solar panel, a layer of N-type semiconductor material is in contact with a layer of P-type semiconductor material, forming a semiconductor junction at the point of contact. Conductive plates are attached to each side of the N and P layers, which are then connected to the power output leads. The diagram below shows how they are constructed:

Check out our article on transistors for an in-depth explanation of how a semiconductor junction works.

Free electrons in the N-type material bond with the electron holes in the P-type material at the junction, forming a charge layer. At this point, no current flows.

When photons from the sun’s energy strike the junction, the bond breaks and the electrons and electron holes are forced back into their layers towards the terminals. If the terminals are connected to a circuit, an electrical current will flow.

How to Build a Solar Powered Battery Charger

In this project, we will build a solar powered battery charger that can provide remote power to any device powered by 5V USB cable, like a cell phone or Arduino project. Here is a diagram of the project:

We will use two 3.7V 2600mAh lithium batteries to store the power generated by the solar panel. We will use the TP4056 battery charging module to take the power from the solar panel and charge the battery safely. The TP4056 battery charger accepts an input from 4.5V to 6V and regulates the output charge to the battery. All that remains is to choose a solar panel capable of outputting 6V.

I decided on a 6V 4.5W solar panel. The output current for this is 4.5W / 6V = 750mA. If we assume an efficiency of 85%, this will give us 640mA. As the two batteries in parallel have a total capacity of 5200mAH, we will need to charge them for 5200mAH / 640mA = 8.1 hours at least.

The batteries operate at 3.7V, so we will need to step up the voltage to 5V to allow for USB charging. We can use a 3.7V to 5V step up converter module to do this. However, keep in mind that this module can draw 2A of current, but the maximum current of the TP4056 battery charger is only 1A. If you charge devices that can draw 2A, you risk burning out the TP4056 battery charger.

Here’s the completed circuit:

The red and black wires are connected to the solar panel. There is also a red slide switch at the top right to turn the module off when not in use.

Home and Industrial Solar Installations

The solar powered battery charger is nice, but what if we want to use solar power in bigger projects like supplying power to a home?

If you connect solar panels in series, the voltage of each panel adds up to a higher voltage:

If solar panels are connected in parallel, the voltage stays the same, but the current from each panel adds to a greater current:

So it is clear that with clever use of series and parallel combinations, you can get the system voltage and current you require.

Just like in the solar powered battery charger project above, you also have to consider the maximum voltage and current ratings for the charge controller and batteries.

Calculating Solar Panel Size

Let’s assume we want to add solar panels to a small holiday bungalow.

First we need to calculate an estimated daily kWh usage. To do this, find the wattage rating for all of the appliances in the bungalow. Then estimate how many hours each appliance will be used on an average day. Now calculate the watt-hours (Wh) for each appliance using this formula:

Watt-hours = watts hours used

For example, the watt-hours of a 500W refrigerator that operates 12 hours per day is 500W 12 hours = 6,000Wh.

Allowing for losses and an inefficiency of 30%, we should multiply the watt-hours by 1.3 to get 6000Wh 1.3 = 7,800 Wh.

Now find the “average daily sun hours” for your location, which can be found by searching online. Now we can calculate the size of solar panel (in watts) that will be needed to provide the watt-hours calculated above.

To do this, divide the daily watt-hours by the number of average daily sun hours. For example, with five sun hours per day in the example above, the size of the solar panel would need to be:

So we need a 1,560W solar panel (or larger) to provide the required power. This can be split up into multiple panels though. For example, assuming we buy 100W solar panels, we would need at least 16 panels.

Hope this article has helped you learn how to set up and use solar panels in your own projects! Be sure to leave a comment below if you have questions about anything.

Method 2: Make a Solar Battery USB Charger

Solar battery USB chargers are compatible with iPhones, tablets, mobile phones, lithium ion batteries and GPS devices. The difference between this charger and the one earlier is you wil be using a battery.

Required Materials

• A portable solar panel
• Battery holder (AAA or AA)
• 1N914 blocking diode
• 1/8 inch wire
• 1/4 in. heat shrink tubing
• Case for charger storage
• USB charging circuit
• Super glue
• Wire stripper
• Soldering iron

Instructions

• Solder the negative side (black) of the diode onto to the solar panel’s red wiring. It should be facing away from the solar panel.
• Put heat shrink tubing on.
• Solder some fresh wiring onto the diode’s positive side. Not a lot, just a few inches is fine.
• Twist the battery holder’s negative wire (black) onto the solar panel’s black wiring. You should end up with parallel wires. The battery holder wiring and the panel should also have a connection newly opened. Repeat these steps for the red wire.
• Get a USB charging circuit and find the and – signs. Get the solar battery / panel wiring you just made and solder them onto the circuit’s and – points. Do this slowly.
• Glue everything inside a case. Sturdy tape will also do.
• You’re done. All that’s left is to test the charger. Get some charged batteries, set them in the charger case and plug in your smartphone. If the charger isn’t working, there might be a problem with the soldering points. If it is charging, get some dead batteries and watch the charger restore them.

Tip: install a second solar panel and place a diode between the two. This will allow you to charge larger, more powerful devices and much faster too. By hooking up the black and red cables between the battery case and the panel, you’ll get a nice charging light.

Method 3: Make a Lithium Solar Battery Charger

As you might have guessed, this is for recharging lithium ion batteries. Most mobile phones today use lithium battery, a testament to its quality and dependability.

Required Materials

• Super glue
• Wire stripper
• Soldering iron
• Storage case for the charger
• Battery holder (AAA or AA)
• 1N914 blocking diode
• Portable solar panel

Instructions

• Just like the previous method, start by soldering the diode’s negative side (black) onto the solar panel’s red wire (positive).
• Apply the heat shrink on the battery holder wires.
• Solder the battery’s negative wire on the solar panel black wire. For the red wire, Solder it onto the diode.
• Put the system in a case or small tin box. Glue or tape everything.
• Test the charger.

Pure Solar Battery Charger vs. Battery Solar Charger

Direct or pure solar USB chargers are very light and easy to make. Just strip a USB cable, stick to a solar panel and it’s good to go. The solar panel does the work of converting the sun’s energy.

The drawback is direct USB solar chargers do not generate a lot of power. They are also insufficient for devices that need a lot of amp power. Lastly, direct solar chargers depend entirely on the sun. If it’s cloudy or the sun’s intensity wanes off, so does the energy flow.

Battery based USB solar changers are not as portable, but they’re more practical. You can charge the panel during the day and at night plug in your phone.

Frequently Asked Questions

How Long Does it Take for a Solar Charger to Charge a Phone?

A few hours at least. Battery based USB chargers are faster, but even then expect to wait hours to get a full charge. it also depends on how much you used up your phone. The weather condition also plays a factor.

An iPhone comes with 3.7 volt battery (100 mA). With a 6.5 watt solar array (433 mA/hour) it will take 3 1/2 hours to charge the iPhone (0 battery to 100%). This assumes that the sun is at its peak for the entire 3 1/2 hours, however.

You can make things easier by not waiting for your phone to drop to 0% before charging. It also helps if you keep your solar charger charged up during the day so you can power up your phone at night. powerful solar chargers are becoming available with shorter charge times though. You can also try these tips to make phone charging faster.

How Can I Charge My Solar Battery without the Sun?

Artificial light sources like LED will charge the battery. However it is going to be a lot slower and isn’t practical. You are better off with the sun.

Do Solar Chargers Need Direct Sunlight?

Direct sunlight is not needed for solar chargers to work, but you will get the best results if the charger is directly exposed to the sun. In some cases it may not be possible to place the charger directly under sunlight, but as much as possible try to.

Will Solar Charge on Cloudy Days?

The charger will still charge, but it will be at a lower level and take longer. That’s why it is best to charge during daytime so you get the best results and faster too.

Why Isn’t My Solar Charger Working?

The most common reasons are:

• Check the wire soldering for damage.
• The solar panels are dirty.
• The phone is damaged.
• There is no sun.

Do Solar Phone Chargers Really Work?

Assuming you followed the instructions above, yes, they do work. As pointed out, an iPhone is better suited for a battery based solar charger than the direct type. but for Android and other types of phones, any of the methods above will do.

What Solar Panels Do I Choose?

Any type of portable solar panel will do. Just make sure it has the power needed to charge your phone (and whatever other device you want to charge). Even the cheap ones will do as long as they’re not damaged.

Phase 3: Build the System

I designed this project to require a minimum number of parts and very few wiring connections. I selected a standard Group 31 RV/Marine battery which is designed for multiple deep charge/discharge cycles while still being reasonably priced. I also found an inexpensive plastic battery box, 10 amp in-line DC fuse, and female cigarette lighter receptacle (Here’s one with battery terminal attachments and fuse built in). I decided to use this type of power receptacle for this project since so many portable tools and electronic devices have charging adapters that fit this type of 12-volt DC receptacle. As shown in the photo, I mounted the cigarette lighter receptacle in the box cover and wired it through the fuse to the battery using #10 standard copper wire and crimp on ring terminals. The center post of the cigarette lighter receptacle is always connected the battery positive and the outer shell is always connected to the battery negative (-).

The Solar-Tech 85-watt solar module I selected for this project includes a full-size conduit box mounted on the back. (Note, we had trouble finding a model with attached conduit box, so you may have to improvise when attaching the charge controller. One option is to mount it inside the battery box, and purchase a cable that ends with male and female MC4 connectors (typical of most solar panels). Wire the bare end of the cable directly to the charge controller, and you can use a short, 2-conductor cable with ring terminal ends for quick connect and disconnect to the battery terminals using wing nuts. This also allows for quick disconnect near the panel.—Editor)

Also make sure the solar module is advertised for a nominal 12 volt charging voltage (17 volts peak), as manufacturers are increasing the physical size and wattage of their modules so fewer modules and wiring connections are needed for the same array total wattage. However, this increased module size also requires increasing the nominal voltage to 24 volts (35 volts peak) to keep current and wire size as small as possible, and this is too high for directly charging a 12-volt battery. While solar charge controllers are available to allow a mismatch between the solar array voltage and battery voltage so you could use a higher voltage solar module, these solar controllers tend to have a much higher cost and are too large to use in this very basic portable solar charging system.

I purchased a Morningstar SunKeeper-12 charge controller, which is designed to mount into the standard ½-inch knockout opening in the solar module’s conduit box and is suitable for mounting out in the weather. You can locate the solar charge controller on the conduit box attached to the back of the solar module, if you can find one with a conduit, (or follow the MC4 instructions detailed above).

Phase 4: Estimate Your Power Needs

Each tool charging cycle consumes an average of 7 amp-hours of battery capacity (7 amp charge rate for 1 hour). The Group 31 RV/Marine battery used for this project has 100 to 115 amp-hours of charge capacity, depending on price and brand. To avoid discharging this battery below 50% (which will help increase battery life), we will have approximately 50 amp-hours of useful charge capacity. This equals seven battery tool recharges (50 amp-hour/7 amp-hour) before the RV/Marine battery will need to be recharged. Of course, the actual number of tool recharges will depend on ambient temperature, battery age, and depth-of-discharge of the tool battery.

We estimated this Group 31 solar battery will require 50 amp-hours of solar charging to replace what the battery tool charging took away. Assuming we have an average of five hours of full sun per day, this will require a solar module capable of providing 5 amps of output to fully recharge this size battery in two days. (50 amp-hours/5 amps = 10 hours).

A typical 85-watt solar module designed to charge 12-volt batteries will typically have a peak output of 5.1 amps, so I selected an 85-watt module. This smaller wattage module is also fairly easy for one person to carry, while still large enough to provide a reasonable amount of solar power. Your solar module can be larger or smaller than my 85-watt module selection, which will reduce or increase the number of days it takes to fully recharge the RV/Marine battery.

I have also omitted solar and charging efficiency considerations to simplify our example calculation. I have also assumed a clear blue sky all day, no module shading, and proper module solar orientation. When these factors are taken into consideration, you will most likely only convert approximately 70% of any solar module’s nameplate output rating into useful battery charging. Do not be surprised if it actually takes a little longer to fully recharge the battery you select.

Phase 5: Put it to Work

It feels really rewarding to build something off-grid in a remote area with the convenience of labor-saving power tools without having to deal with a noisy generator. It’s also nice to have a portable solar-charging system instead of having to keep your truck running while using a DC to AC inverter to power your tools and tool chargers. When not needed to recharge power tools at a job site, this portable solar-charging system can be used for camping or during emergency power outages. This solar module with built-in solar charge controller can even be used to recharge your RV camper batteries when dry camping.

While most major manufacturers of battery-powered hand tools offer an “in-vehicle” charger, these are not easy to find in your local retail store. If you cannot find them locally, there are several Internet sites that sell in-vehicle chargers. Order the charger that matches your brand of battery-powered tools, and be sure the charger matches the voltage and chemistry of your battery packs.

DeWALT #DC9319 7.2-volt to 18-volt vehicle charger:

Makita #DC18SE 18-volt/Lithium-ion vehicle charger:

Bosch #BC006 7.2-volt to 24-volt vehicle charger:

Milwaukee #M12 12-volt Lithium-ion wall and vehicle charger:Milwaukee #M18 18-volt Lithium-ion wall and vehicle charger: This is one of the few that is also an A/C charger, so it’s double-your-value.

Ryobi One 18-volt dual chemistry in-vehicle charger:

About the Author: Jeff Yago is a licensed professional engineer and certified energy manager with more than 30 years of experience in the energy conservation field. He has extensive solar and emergency preparedness experience, and has authored numerous articles and texts.