I think that those usb chargers probably work better if they are charging a battery anyway. Last I looked, Anker still made batteries with pass-through charging. My only experience with USB chargers was a Luxos U headlight, which might not be the best example. But the first time I used it to charge my GPS, it was infuriating. The route featured 50 miles of gradual uphill, so the charger was continually dropping out and a Garmin 800 is programmed to beep and put up a message every time that happens.