Do you mean one of
those used to recharge a cell phone or tablet? I have several of those, including one that is 30,000mAh capacity. One of the power packs could run your 325P2 for quite some time, or charge the batteries if it were turned off.
To charge the batteries, while powering the scanner, if you had an extra set of batteries that could be charged using the power pack, you would need a battery charger that works on 5 volts, such as
this. There are a number of other AA/AAA chargers that run off 12 volts. I have a power pack, part of one of the jump start kits, that has 12v output (in addition to the jump start function), and also has a 20v output, with various cable tips, to charge laptops.
For one of the scanners that will both charge and run with 5v input, such as the 436HP or SDS100, I use one of the higher capacity packs if I'm mobile in a vehicle that does not have a 12v port,