I stumbled across this earlier today while surfing, an external battery with high-amp (4.8 A!) USB ports and an AC plug (100 W or 65 W draw): https://www.indiegogo.com/projects/...-powerbank?gclid=COzJ_cTA0c4CFZA1aQodW1cE5w#/ The company website is www.omnicharge.co The device comes in two capacities: 49 Wh (Omnicharge13) or 73 Wh (Omnicharge20). Based on the pictures and specs that would be 4 x 18650 or 6 x 18650 batteries, respectively. The batteries appear to be Panasonic, an excellent choice. I've asked for a little more information from OmniCharge and will report back if I find anything significant.