Adrian Kingsley-Hughes/ZDNETZDNET’s key takeawaysSolar-powered power banks can be unreliable and potentially unsafe.They are ineffective at charging devices, even after prolonged sun exposure.Safer and more reliable alternatives, like a solar power station, are recommended.Solar-powered power banks seem like a fantastic idea; attach some solar panels to a power bank, and you have a free power source whenever the sun is shining.However, the reality is different from this idyllic vision of limitless energy.Also: I jump-started a bus from the 1930s with this power bank – here’s the verdictI’ve tested nearly two dozen solar-powered power banks, ranging from devices purchased online to ones bought from camping and outdoor supply stores. Unfortunately, every single device has been disappointingly ineffective — and some have even been potentially dangerous.Using such a device means placing a power bank, a box filled with lithium-ion batteries, in direct sunlight. And that’s a big problem. I’ve found that a power bank left in the sun on a modestly hot day can hit temperatures as high as 80°C/176°F, which is incredibly hot for lithium batteries. More