This is dependent on charging frequency more than the charger itself. The batteries only go so many charges before they start losing their capacity. This is true of any charger, really. I keep my iphone on a charged dock at work and on a charger while in the car, and realize this may shorten it's battery life over time since I'm not draining it and fully charging it, but instead doing a higher frequency of shorter charges.Now, will this decrease the battery's capacity over time like I've heard some people say?