Lumsing 10400mah External USB Portable Battery Lumsing Series External Power Bank and Portable Battery Charger. The Lumsing Harmonica is a powerful, high-capacity battery charger packed Giveaway. This Lumsing 10400mah External USB Portable Battery Charger Power Bank. Is the second one of these that I have purchased because they work so well. We used this on our last trip to Disney. Due to a heavy cell phone used for their apps and pictures, as well as texting other members of our group when we split up. This little baby completely recharged by S7 twice while simultaneously recharging my sons Verizon phone and still had juice left. I also like the\u00a0Lumsing function that you have to press the button on the side to begin charging, to prevent accidental charging of a connected device in a bag or purse. Easy To Use The Lumsing 10400mah External USB Portable Battery. Recharges completely easily overnight. The item is bulky (thicker than most I've seen and shorter than most phones). But I have big hands and with The\u00a0Lumsing directly behind my phone was easily able to hold both at the same time when in use.