The SprkCharger Slim and Wallet are designed to allow a single wall power charger and cable to be attached to the Slim powerbank micro-USB connector to charge the powerbank and the phone attached to the powerbank. The Slim powerbank has a special electronic ASIC design that allows pass through current to charge the phone and then also pass current to recharge the powerbank cell.  Great for overnight recharging of both devices with one charge cable/charger.