Amazon claims a month of battery life for its Kindle, but if that's not long enough, one company has created a solar-charging case for the ebook reader.
The SolarFocus SolarKindle cover features a photo-voltaic panel on the front, which charges an extra battery on the back of the device, which can be used to either recharge the Kindle or power the pop-up reading light.
The extra battery pack will triple the reading time of the Kindle to three months and power the LED lamp for 50 hours, the company said.
Leaving the cover charging for an hour in the sun will provide up to three days of reading time, executive vice president Dick Lu told PC Pro at CES.
SolarFocus already offers solar-powered charging cases for mobile phones and other devices, but the Kindle cover is the first designed to integrate with a specific device, Lu added, saying it makes sense for ebook readers as "you need a cover to protect the screen anyway".
The extra battery in the cover means the case is thicker than most, but it weighs 250g, only 25g more than Amazon's own Kindle cover with an integrated light. The spare battery can also be charged via USB.
The SolarKindle is available for the Kindle for $79, and versions are in the works for the Kindle Touch and rival ebook reader Nook.
However, the company doesn't see integrated covers for smartphones such as the iPhone working as well, as the smaller size means they need to be left charging in the sun for long periods. "We don't want to make something that won't perform well," said SolarFocus' sales director Allan Shoji.
He said other companies have tried to create integrated solar charging cases for smartphones, but faced troubles with devices overheating after being left in the sun for too long.
He said the design of the Kindle case - with the solar panel on the cover, separate from the battery and the device - means overheating isn't a problem.
This article originally appeared at pcpro.co.uk