I recently made a DIY solar USB charger that, in my opinion, is WAY better than most of the other designs out there.
It’s portable. It looks good. And it can charge your phone and USB devices faster than the mere trickle put out by most other homemade solar chargers.
That’s right — it’s a DIY solar charger that you’ll actually use.
The best part?
It’s affordable and easy to make.
Here’s how to do it.
Materials & Tools
Materials
- 2 3W 9V solar panels
- Stranded wire (I used 22 gauge wire)
- 5V DC/DC Buck Converter
- Glue (a hot glue gun is pictured, but I ended up using E6000 craft glue)
- Reusable grocery bag
- Heat shrink tubing (optional)
- 4 1/4″ eyelets (optional)
Tools
- Wire strippers
- Soldering iron
- Scissors
- Safety glasses
- Multimeter
- Heat gun (optional)
- 1/4″ eyelet tools (optional)
- Hammer (optional)
Step 1: Prep the Fabric
For this design, I upcycled an old reusable grocery bag to cut a strip of fabric to which I attached the panels. It protects them and allows them to fold up for easy storage.
Place the panels, eyelets (if using), and DC/DC buck converter on the reusable grocery bag in your desired layout.
Tip: I recommend giving yourself 1″ or more of space between your solar panels so they can fold easily. I also gave myself more length than necessary so I could fold the fabric over the buck converter, as you’ll see in Step 6.
Cut the fabric to your desired dimensions with scissors. (Mine ended up being about 14″ long by 8.25″ wide.)
Step 2: Wire the Solar Panels in Parallel
Cut a length of wire to connect the panels’ positive terminals. Give yourself some slack in the wire so it isn’t pulled taut when the panels are folded.
Note: Because my panels have two pairs of terminals on back, before wiring I used a multimeter to check their voltages. It turned out the terminals that output 9 volts are the two “top” terminals — not the terminals with the “+” and “-” signs. Strange.
Strip and solder the wire from positive terminal to positive terminal. (I decided to orient my panels in opposite directions to lessen the stress on the wire when the panels are folded.)
Tip: Keep your solder joints as flush as possible with your solar panels. This helps later on when gluing them to the fabric.
Cut a length of wire to connect the panels’ negative terminals. Once again, give yourself some slack.
Strip and solder the wire from negative terminal to negative terminal.
Step 3: Solder the Leads to the Panels
Cut a length of wire for the panels’ positive lead. It will connect one of the panels’ positive terminal to the buck converter’s positive terminal. Make sure it can reach where you want to place the converter. Don’t forget some slack!
Strip and solder the positive lead to one of the panels’ positive terminal.
Cut a length of wire for the panels’ negative lead.
Strip and solder the negative lead to one of the panels’ negative terminal.
Now let’s test the panels’ voltage and amperage outputs with a multimeter to make sure we wired everything correctly! Connect the meter’s positive probe to the positive lead and its negative probe to the negative lead.
What outputs should we expect?
Well, here are the specs for the panels I used:
- 3W
- 9V
- 333mA
Wiring solar panels in parallel adds the current (amps) together while keeping the voltage (volts) the same.
Thus, for volts, you should see a number around 9V DC.
Almost 10V DC. Perfect!
For amps, you should see a number around 666mA (333mA * 2). But in real world conditions, expect solar panels to output a little less than their stated current.
Tip: You’ll likely have to switch the red probe to your multimeter’s other port in order to measure this amount of current.
557mA. Check!
Step 4: Solder the Buck Converter to the Leads
Locate the positive and negative terminals on the buck converter.
Solder the positive lead to the converter’s positive terminal and the negative lead to its negative terminal.
Now you should have a working solar charger!
Time to check that it’s working.
First, make sure the buck converter is connected properly and working by shining some light on the panels. Its LED should light up.
The LED is on. Looks like it’s working. ✅
Next, test your charger by placing it outside in direct sunlight and plugging in your phone or USB device. Your device should start charging.
My Kindle’s charging light turns on when I plug it in — my charger is working!
I tested my charger’s output with a USB meter to confirm that the charger was indeed outputting a decent current at 5V.
It’s outputting 460mA (about half an amp) at 5V. That’s about 2.5W, or half the rate of a standard 5W phone charger. (During real-world use it regularly got up to 3W.)
According to our solar charging calculator, it will take about 10.8 hours of direct sunlight to fully charge my iPhone XR.
Definitely not the fastest solar charger, but it’ll top off my battery in a pinch.
Optional: Shrink wrap the buck converter using heat shrink tubing and a heat gun. I did this to for aesthetics and to protect the circuit board a bit. It covers up the converter’s LED, but that wasn’t a big deal to me.
Step 5: Glue the Charger to the Fabric
Grab your glue and the strip of fabric you cut back in Step 1. Glue the panels and buck converter to the fabric in your desired layout.
Tip: The glue I used bled through the fabric a bit, so you may want to put a piece of newspaper down first.
Wait for the glue to set. Once it has, touch up any spots you missed, if needed.
Step 6: Install the Eyelets (Optional)
Because I’ll be using my charger while hiking and biking, I wanted to install eyelets so I can strap it to my backpack and bike. If you don’t need to attach your charger to anything, you can skip this step.
First, let’s install the two eyelets at the “bottom” — the side opposite the buck converter.
Cut a circle in the fabric using the eyelet as a guide. Feed the eyelet bottom through the hole.
Tip: Since I used such small eyelets I just cut a small X with my scissors. You could also create a hole by poking a nail through.
Place the eyelet base tool underneath the eyelet bottom. Place the eyelet top on top of the fabric.
Place the eyelet punch tool over the eyelet top. Hammer the punch tool to install the eyelet.
Repeat these steps to install the second bottom eyelet.
Now it’s time for the top eyelets — the ones on the same side as the buck converter.
To protect the converter, I decided to fold the extra fabric over it and cut a hole for its USB port. (If you don’t want to do that, just install the top eyelets like you did the bottom ones.)
Then I installed the top eyelets through both layers of fabric, glued the flaps together, and glued the USB port to the fabric.
Note: Don’t cover up any of the solar panel!
Wait for the glue to set, and you’re DONE!
Step 7: Test Your DIY Solar Charger
Now that you’ve made your own solar-powered charger, it’s time to charge something with it!
Place it outside in direct sunlight. Plug in your phone or other USB device. Then sit back and relax as you take advantage of all that free solar energy.
When you’re done charging, fold the charger shut for easy storage.
This charger doesn’t have a built-in battery. Adding a battery makes a homemade solar phone charger more complex.
You can easily pair your charger with your battery pack of choice (I use the Anker PowerCore II 10000). Charge your battery pack during the day, then use it to charge your phone or USB device at night.
More DIY Solar Charger Projects
1. Solar Electric Bike Charger
Learn how to solar charge your ebike battery for what may be the most eco-friendly transportation method there is. I even show you how I mounted my solar charger to my ebike to make a full-on solar bike.
10 thoughts on “DIY Solar USB Charger: 7 Steps (w/ Photos)”
where did you purchase th panels from and what to ask for ie discription thanks Arthur
I purchased them on Amazon: https://www.amazon.com/gp/product/B00P4W9UE6/
They’re 3W 9V panels.
Thanks for share good ideas Luke this
You’re welcome, Cirilo!
Is there any harm, or advantage to making it with 3 panels? Could it damage the phone (If say, I was in Arizona in June)?
I’m thinking, for less than perfect sunny days, it might not charge the phone as slowly…
Based on my results with 2 panels, I’d expect 3 of those panels wired in parallel to output around 4-5 watts in direct sunlight. (For reference, the standard iphone charging brick is a 5 watt charger, and many fast chargers are now in the 12-18W range.) So yeah, your phone will likely be perfectly happy with that charging speed.
Respect. I built my own portable power station with 30 watt panel that can handle multiple phones etc at once, but I was looking to make yet another gadget that was smaller. Figured if I could get a panel closer to 5 volts to begin with, it could be more efficient than pulling down a 21 volt panel through 12 volt batteries and USB marine chargers.
Love your idea with the recycled grocery bag for the “padded case.”
I’ve had good luck with my panel output but they are all name brand.
Would you say the issue here with the solar output has more to do with the inefficiency in the buck converter voltage drop or the panels themselves? 50% peak is quite a bit lower than expected. Did you do much testing on the panels themselves?
Yeah I think the inefficiency is due to the buck converter. Tested the panels and the voltage and amperage output were as advertised. Tossing around an idea for a “version 2.0” where I use 6V panels instead (something like these: https://www.amazon.com/dp/B00HQXQOIQ/). Would expect efficiency to be much higher in that case since the buck converter would only have to step down from 6 to 5v.
Yeah, I’m not quite getting this either. A decent buck converter should be close to 90% efficient, especially taking 7-8 volts (or whatever the working voltage gets lowered to) and changing it to 5. That’s not a huge drop. I didn’t notice you installing a reverse current Diode between the output of the parallel panels and the buck USB. You might try installing a schottky diode there. That should lower (waste) the voltage at least .3, while preventing current leakage back into the panel. You might try it and rerun your meter test anyway. Perhaps this USB Adapter isn’t great.
I used this one like this for my setup. It’s adjustable voltage, has a USB port- But you better make sure it’s dialed at 5 volts before plugging anything in. it’s sending whatever voltage you have it dialed to through the USB port!
https://www.autochili.com/products/dc-buck-module-drok-adjustable-buck-converter-step-down-voltage-regulator-6v-32v-30v-24v-12v-to-1-5-32v-5v-5a-lcd-power-supply-volt-reducer-transformer-module-board-with-usb-port-protective-case?gclid=CjwKCAjw7J6EBhBDEiwA5UUM2jsL6CkFDeKBhS2nbOaIyIU9Gw1lp_DcEyal9C1XkAULER49QK9g-RoCiBwQAvD_BwE
Yeah starting to wonder as well if the buck converter is just a low-quality one. It is pretty cheap. I looked at something like the one you linked to for this build, but went with the smaller one because of its size. Maybe for an updated version I’ll upgrade to a nicer one like that. And appreciate the tip on the diode addition!