A 12V motor cycle or lawn mower battery will run a standard radio for hours. They are easier to hide than a second car battery. Keep it on a trickle charger when garaged.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.