No, you don’t. You can charge the smartphone battery WITH BETTER RE. Just think of BETTER RE as a case of an external battery pack. What differentiates BETTER RE from common external battery packs is that you can replace the battery that goes into BETTER RE.
BETTER RE will be ready to charge your devices through either of the following ways:
1. Charge BETTER RE with a smartphone battery (in need of charge) inside, just as you would charge an external battery pack.
2. Clip a fully charged smartphone battery into BETTER RE. If you carry a number of batteries around, you can charge your device multiple times by simply replacing the batteries!