I played electric guitar for a Morris side back in the 1980s before the era of modern busking amps. The problem we had was making an amp loud and undistorted enough on battery power. I bought a 50 watt power amp which required, I was told, 80 volts DC to work to full potential. After trying banks of largest size 9v batteries, which expired after 10 minutes, a fiend suggested using a couple of 12v motor bike batteries which could provide the high amount of current needed by the amp. That worked, and with a high gain preamp, provided plenty of undistorted volume which could be heard by the dancers over the noise of traffic.