Jamie Matthews' Bluetooth Supercap Speaker Harvests the Sun's Rays to Keep the Tunes Coming
Energy-efficient design offers unlimited playback in direct sunlight, and up to eight hours in darkness from a 10-minute USB charge.
Maker Jamie Matthews has built a Bluetooth speaker with a difference: it has no battery, relying instead on a series of supercapacitors topped up by a compact solar panel.
"We are currently experiencing a massive energy crises in South Africa where we are left without any electricity for four hour intervals throughout the day during a nationally implemented 'loadshedding,'" Matthews explains of the project's inspiration. "As a result there is a requirement for energy saving and green energy devices.
"Why not just use batteries? There are so many reasons supercapacitors are much better suited for low power applications like this, most modern 18650 batteries have a typical cycle life of 300 - 500 (charge, discharge cycles) whereas supercapacitors have 100,000 to a million life cycles!"
In Matthews' case, those long-life supercapacitors are being used to drive an amplified speaker that works whether mains power is available or not — charging them up using a solar panel on the top of the 3D-printed housing. "With the current setup I get a minimum of six hours playtime from a full charge without solar, this is thanks to the TPA2013D1 class D amplifier that has 87.5%+ efficiency and a built in boost converter that keeps a constant 5.5V even as the supercapacitors deplete," Matthews reports.
"If the speaker is placed in a sunny windowsill or outdoors so that the solar panel is in the sun there is absolutely no voltage sag on the supercapacitor when listening at maximum volume."
In the speaker's original design, audio was fed using a USB Type-C connector which could also be used to rapidly charge the supercapacitors when sunlight wasn't available — offering up to eight hours of playback for a ten-minute charge.
Having discovered that the supercapacitors in use offered plenty of power, and that a sufficiently sunny position would result in basically unlimited playback times, Matthews then added Bluetooth audio support — smartly creating an add-on module which just hooks into the speaker's USB Type-C port at the rear.
Matthews' full write up, including circuit designs and 3D-printable files for the housing, is available on Hackaday.io.