Can a compact solar USB charger charge a phone and an external battery at the same time in about 3 hours? Yes! This is an Open Source Hardware instruction manual on how to build the Solarpad Kit solar USB charger, which includes the Solarpad solar panel and Power Core USB battery.

Why Open Source Hardware?

The solar USB charging market has become saturated with low-quality and poor performing products and every year the big companies are selling the same products with very little improvement. Therefore, Solarcycle has developed its open source solar USB charger to empower customers with the ability to build their own solar USB chargers and to prove that a better solar charger that outperforms anything else on the market is possible. This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

What's Special About Solarpad?

Our Solarpad Kit sets a new standard for a rugged, lightweight, compact, powerful, water resistant, and easy-to-use USB solar charger that can keep a smart phone charged all day! Connect Solarpad to the Power Core battery input then use the cable that came with your smart phone and plug it in to the Power Core output. Solar charge the Power Core battery and charge your phone from this battery at the same time! We designed the Solarpad Kit without an on/off button so you just plug it in and it works automatically! If a phone has a unique connector, one end of its charge cable always has a standard USB compatible plug. No extra cables are required because they are built-in. Use the Solarpad Kit on your next adventure! Will not leave you powerless.

The Solarpad Kit is designed to outlive the life of your Smart Phone! Solarpad uses a high-quality, custom Suntactics solar panel, which has a fluoropolymer film with the best light transmission, precision cut and tabbed high-efficiency solar cells, and a high-strength substrate. The panel is attached to a housing, which holds the buckle straps and 1/4-20 tripod thread in place. Our Power Core battery uses a high-efficiency, high-power charge controller from Maxim and the housing is sealed with high-strength epoxy, which prevents water from leaking in. Also, Power Core uses the same battery that's used in the Tesla electric car, which is the best battery of its kind. Even the built-in USB cables consist of thicker gage wire, which allows the electricity to flow more efficiently. The Solarpad Kit is engineered to squeeze the most energy possible from the sun's rays in to your smart phone. No short-cuts that compromise power or efficiency are taken, period.

HOW THE CIRCUIT WORKS: The Maxim chip uses Smart Selector Technology, which passes and regulates solar energy directly to your phone as a priority and stores excess energy to Power Core with up to 2000mA going through the circuit. When the solar energy decreases, Smart Selector Technology instantly uses power stored in Power Core to compensate for any loss in solar energy to keep your phone charging.