I recently bought one of the best solar power banks to give it a spin. In particular, I wanted to test the power bank’s solar charging feature.
Does it work? Can the power bank meaningfully charge your devices from the solar panel alone? Or is the solar charging feature just a gimmick?
Let’s find out.
Video: Testing a Solar Power Bank
Here’s a short video of my test. Check it out and consider subscribing to my YouTube channel for more tests and reviews of solar products.
How Well Do Solar Power Banks Work?
Before the test, I drained the power bank entirely using a USB load tester. That way, any energy I measured from the power bank would be entirely from solar.
I woke up early before sunrise to put the solar power bank outside in a sunny spot in my backyard. I’m fortunate that my yard is an ideal testing spot for solar panels.
The day was a mostly sunny day with the odd cloud here and there. Once the sun had set, I brought the power bank inside, plugged my phone in (an iPhone 14 Pro), and used a USB meter to measure how much energy the power bank had collected.
Here were the results:
The USB meter measured a total output of 1.72 watt hours. For reference, the iPhone 14 Pro has a 12.38 watt-hour battery and the Google Pixel 8’s 4,575 mAh battery works out to 16.93 watt hours at 3.7 volts.
And, in practice, my iPhone 14’s battery increased from 45% to 54% — a 9% increase.
I’m quite familiar with the output of solar panels. Hell, I’ve been testing them for years at this point. So this measly output didn’t surprise me too much. The solar panel on the model I bought is just so small that I knew it would output barely anything, even over an entire day.
For comparison, here’s the solar power bank’s size compared to the BigBlue 28W Solar Charger, a popular and well-rated solar charger.
There’s no way around it: you’re just not getting lots of solar power from a panel that small.
And then there’s the fact that lithium batteries shouldn’t get too hot. If you’ve ever left your phone in direct sun for longer than 10 minutes, you’ve probably gotten a warning that its battery needs to cool down before you can use it again. However, for solar power banks to do their solar powering, they need to be in direct sunlight. It’s a weird catch-22.
When I posted the video of my test to YouTube, commenters mainly fell into one of two camps. Either they thought the solar power bank was a waste of money, or they thought that it could be a useful product to have in an emergency.
To be fair, the solar power bank’s instruction manual warns that the solar panel should only be used as a “backup source” of power. The main source? Standard wall charging, like any other portable charger.
Solar power banks work, but heavily temper your expectations of their solar charging capabilities. It will take most models multiple days of sunny weather to meaningfully charge your phone or any other device. And that’s with the power bank outside in direct sun, not simply behind a window.
You could buy one for emergencies, but you’d still have to wait a while before you could charge a dead phone enough to make an emergency call. The exact length of time would depend on the model and weather conditions, but I’d expect a few hours.
Single-panel solar power banks are the most popular version on the market today. But, for a faster charge, I’d recommend getting one with multiple panels. Or — and this may be the best option of all — buy a dedicated solar charger and pair it with a good battery pack.