The idea behind power banks with solar panels sounds great: you charge devices using solar power, which is usually plentiful, without relying on a power outlet. Theoretically, this looks like a one-time investment. You get a solar power bank, charge it in the sun, power your devices and the cycle continues. But the reality is very different. Power banks equipped with solar panels are generally not as reliable as standard batteries and they also pose a safety risk by the very fact that they charge in the sun.
To be clear, there is no doubt that solar power banks, whether they feature one panel or multiple panels, do their job. They can charge your smartphone or run other low-power devices like small LEDs and portable fans. The problem is that most people expect them to perform the same as a standard fast-charging power bank, and that’s where these devices fall short. Most solar power banks on the market do not fully charge within a few hours or even a day or two, even when exposed to direct sunlight.
Additionally, under the sun, solar batteries can get very hot, with temperatures often reaching over 150 degrees Fahrenheit. This exceeds the safe operating limits of lithium-ion batteries commonly used in power banks. In addition to reducing battery life, higher temperatures also increase the likelihood that onboard controllers will interrupt charging altogether to reduce heat levels. Even some manufacturers advise against leaving power banks in direct sunlight for too long.
External batteries with solar panels are not as reliable
The biggest disadvantage of power banks equipped with solar panels is that they need a long time to generate enough power to fully charge even a smartphone. This is mainly because the attached panels are relatively small and can only generate a small amount of electricity.
For example, when placed outdoors for two days, power banks with a single panel can generate between 0.8 watt hours and 1.5 watt hours of energy, while those with multiple panels typically generate six to nine watt hours. To give you an idea of how small it is, the iPhone 17 has a battery capacity of 14.5 watt hours. So, on average, you get 10-65% of an iPhone 17’s battery after charging the power bank for two days. On the other hand, a standard 10,000 milliamp-hour power bank will charge in four to six hours and can typically provide two full charge cycles for your iPhone 17.
Keep in mind that there are other factors at play here too, things beyond your control. For example, if there is little or no sunlight, if the panels are placed in partial shade, or if they are covered in dust, the power bank will take much longer to charge, making it unreliable as a primary power source in critical situations. So, from a reliability perspective, external batteries equipped with solar panels are not a practical everyday solution for most use cases, at least in the current context. Newer and better technologies could, of course, make them more viable in the years to come.
Use solar power banks as backup solutions
Despite all the limitations, there are cases where external batteries equipped with solar panels prove useful. Many people rely on them in areas with frequent power outages or in places that don’t receive electricity at all. This is because standard power banks are of little use here, while those equipped with solar panels can generate enough power to run your phone and other essential accessories, at least for a while. If you’re looking to generate more power, you can opt for power banks that have multiple solar panels. Unsurprisingly, those with one panel attached to the body generate less energy than those with multiple panels attached. Likewise, if you go on long hikes or spend time in remote locations, these power banks can be a valuable addition.
Additionally, the most reliable power banks with solar panels can also be charged from a wall outlet. So this could be your initial charging source, while connected solar panels can provide additional power over time for as long as you’re away from a charger.
That said, traditional external batteries remain the most reliable choice for everyday use. Solar power banks remain a niche product aimed at a limited set of users. Over time, the list of use cases they can handle well may grow to become the primary source of power, but for now they should be considered primarily as fallbacks.
