If you run your amps at the verge of blowing the fuses (50A), they would drain an average battery (60-100 Ah) in half an hour. However, nothing is stoping you from turning the volume down (10dB quieter should be enough to make the battery last few hours). As for recharging, see your alternator data - nowadays they give at least 50A, more likely 100, but I have no idea at what RPM.

Dry run suggested by Doug is the only sure way of knowing, but lacking that, take a voltmeter (best a cheap analogue one - to avoid draining its battery) or simply crank the engine as soon as the battery icon appears on the empeg.

Have a nice time! (hm, I just realized that this reply is late by at least a day )