Update: Batteries and charger broke completely within months of use. I had to buy a completely different set of batteries and chargers and it worked fine. Old review: I bought these rechargeable batteries as I kept using regular batteries just to power the Xbox controller. It fits perfectly on the back of the controller. I haven't had any charging issues so far. You just plug it in and wait for the light to change from red to green. It's very easy to use!