How fast your power bank can charge a device is dependent upon the available output of the power bank and the available input of the device. Without getting too much into the electrical details, a standard 3,000mAh device such as a smartphone can be expected to charge in about 90 minutes by most power banks. However, many power banks nowadays come with quick charge technology, which helps speed up the process even more. Larger devices such as tablets and laptops may take much longer to charge as they require much higher inputs than smartphones. Always double-check that the power bank you want has an output that matches or exceeds the input of your device to ensure the fastest possible charging.