The auxiliary battery we supply is for this purpose.
You just need to ensure you connect the battery to the Catalyst DA1 antenna before you connect to your smart phone, this then enables the phone or tablet to draw a charge from the powered antenna.
If you follow the setup order in the Catalyst Quick Start Guide to get this working, you'll see immediately your phone or tablet battery icon indicate it is charging.
In Trimble Mobile Manager you will see a small battery icon on the home page under the device menu (see screen grab below)
NB - on some devices the battery icon in TMM fails to disappear when you disconnect the battery without an app refresh so you should double check against the phone or tablets main battery icon that the device is charging
If you don't have an auxiliary battery take a look at the Catalyst website Shop Now page and the hardware tab for details on optional accessories, replacements and spares including the External USB battery pack (3350 mAh) PN 103635-00