The portable battery chargers magnetically attach to the Scollar Mini so you don't have to remove the Scollar from your pet. When attached to the Scollar Mini, a full charge will be achieved in less than two hours! A fully charged portable battery charger can provide two full charges of the Scollar Mini, and the portable battery charger can be charged by either the Scollar Base Station or through a micro-USB cable. Every Scollar Mini comes with the portable battery charger and USB cable. Think of it like the backup battery you may use for your smart phone.