I purchased a solar backup with a battery kit. Sunsocket DUO-flex a few years ago. it does the job. light and will recharge any type of battery pack with the usb connection.
The battery that comes with this will recharge bout 1.5 times. now a days... seems technology has massively improved to smaller batteries that will double and even triple the recharges for a phone. Meh, the recharge gives me assurance I will be able to recharge my gps, phone, etc.