#1
the 20 watt one.

or any battery powered portable bass amp you might have.

how long do the batteries last?

any downsides to these type of amps?

thanks
#2
What's the reason you are looking into battery powered amps? I own a Pignose amp; its OK for bedroom practice, outside gigs with acoustic guitarists. But honestly 20W is not a good gigging wattage.

The battery on the Pignose H30 and 50s lasts about 6 - 9 hours. In the 6 years I've owned mine, I've had to replace the batteries once.