To streamline battery charging, the battery charging hub supports charging two batteries at the same time with dual slots. Built-in USB Type-C connector supports power supply from the built-in power supply or a common external USB battery (sold separately). The front LED indicates charging status and capacity. You can also check the remaining battery power by simply inserting the battery into the battery charging hub and pressing a button once. The battery charging hub supports both 1st generation 3200mAh X system batteries and current 3400mAh batteries. The latter supports fast charging up to 25% faster than the former. It fully charges one rechargeable battery in 2.3 hours and two rechargeable batteries in 2.8 hours. The 1st generation 3200mAh battery fully charges in approximately 3 hours. In either case, you will be notified with a sound when charging is complete.