Introduction: Making the Most From a USB Solar Charger

About: I run the Maker Project Lab blog, and a weekly video series called Maker Update. Email me at

In this Instructable I'm going over some tips I've learned in my experience using a USB solar charger. Specifically, I've been using the Anker 15W PowerPort Solar over the past six months after buying one on the recommendation of The Wirecutter, which named it their Best Portable Solar Battery Charger.

I figured it would be my way of dipping my toe into solar power and I've been using it every week to recharge a handful of USB battery packs I have. At night, I then use those packs to charge my phone.

It's worked out well, but I made some mistakes along the way and learned a few things. I've also made some modifications that I recommend. So I figured an Instructable would be a good way to collect all that.

(Disclosure: This is not a sponsored post. I bought everything here with my own money and my opinions about it are my own. I have no association with the manufacturer of any of these products. The reviews site Cool Tools, does pay me to publish my opinions and videos on tools I enjoy, and I've included one of my videos here. Also these Amazon links kick back a little money to me if you use them.)

Step 1: Direct Makes a Real Difference

When I first bought this solar charger, I figured I could simply prop it up in a window in my room and charge things up while I did other things. But it turned out that even with bright sunlight outside, the window significantly cut down on my charging performance.

I consulted the instructions, wondering if maybe I had a defective product. I read the bit about placing the charger "in direct sunlight for best performance". This turns out to be very true, and I suspect is generally true for any solar product.

I hung the panel outside the following day and it charged my portable battery right up.

I don't understand the science of photovoltaics, but I can say from experience that a solar charger really benefits from being outside, pointed directly at the sun.

Step 2: Find Your Spots

Unfortunately, the sun is a moving target. It reliably rises in the east and sets in the west, but it never stands still.

In my yard, I have one spot facing East that's great for capturing the sunlight from sunrise to around noon. From noon to dusk, my house blocks the sun from that spot and I will sometimes move the charger to another location that faces South.

Depending on your location and the buildings and shade around, you may need to come up with your own solution for where and how to position your panel.

Moving it around mid-day can be a bit of a hassle, but if I'm at home and I notice the sun shifting, it only takes a minute.

Fortunately, this particular panel includes a bunch of useful braided loops that you can just pop on a hook or a nail. As an alternative, I used some screws with a wide head and drilled them part way into the fence in my yard. I wrapped the exposed threads with gaffer tape to prevent them from eating into the loop material. It's worked out well so far.

Step 3: No All-nighters

So here's another false assumption I made. I figured that since most home solar panels are left out at night, that it would be alright if I just left my solar charger out overnight too. I was wrong.

I'm sure that more sophisticated solar panels have intelligent systems to shut down charging below a certain threshold of light, but for better or worse, my charger will try to charge things using even the dimmest bit of sunlight.

The result is that dim light will stimulate the charge circuit on a battery or device just enough to keep it open, but not enough to actually charge. During the hours of dusk and dawn, this can lead to devices actually losing more power than they gain, or sometimes reporting more charge than they actually have.

For example, I had a few times when I left a low battery charging for several days, leaving it out overnight, only to check back on it and find it at 75% charge day after day.

Only later did I realize that the battery was losing charge during dawn and dusk.

By putting the charger out first thing in the morning and collecting it before dusk, I'm able to get even my biggest battery fully charged if the day is sunny enough. That said, I'll often forget the charger is out there and leave it overnight accidentally, only to give it another try the following day.

Step 4: One Device at a Time

This particular solar charger boasts two USB charging ports, leading you to believe that you could conceivably charge two devices at the same time.

But that's unrealistic. By trying to charge two devices off the same panel, you're really just lowering the charge rate of both devices.

Instead, charge one device at a time and content yourself with this minor miracle. Better yet, use a single port to charge up a USB battery that has multiple USB ports.

Step 5: Charge Batteries, Not Gadgets

This solar charger and many like it are sold under the premise that you'll use them to directly connect and charge your cell phone or tablet. I think that's an inherently stupid idea.

For one, placing your phone in the charger's black pouch in direct sunlight is an invitation for all kinds of overheating problems. If the phone thinks it's too hot, it will shut down and prevent the battery from charging.

Second, most of us use our phones during the day and charge them at night. But direct solar charging forces you to flip this formula.

The simple solution to this problem is just to buy a USB-rechargeable battery or two to load up during the day with the solar charger. Then, you can charge your precious devices at night from the battery.

Naturally, this charger doesn't come with a battery, so you'll need to get one separately (by no coincidence, this same company makes USB batteries and is happy to sell them to you). But once you connect up a battery, it's still not the smartest idea to leave it out in direct sunlight tucked into the chargers black pouch.

My solution was to store batteries in a separate, insulated battery bag while they charged up. In fact, I glued my bag to the back of the solar charger with some E6000 adhesive, and it's held up surprisingly well over the past few months.

I also found that using a right-angle micro USB cable to go from the charger to the battery helps reduce the cable strain and makes the fit less awkward.

Step 6: Final Thoughts

Ultimately, I'm really glad I got this charger. It's a small point of pride for me that my phone has essentially run off solar power for the past 6 months now. I only wish it hadn't taken so much trial and error to understand how to optimize my own charging ritual with this, but hopefully these tips will make it easier for you.

I'd like to take on a bigger DIY solar system somewhere between this panel and a full blown roof system that I'd probably have to get a permit for. If you have suggestions of what I should do next, I'd love to hear it.