Why wont my battery power my amp? oh yea i cant comment so don't ask questions lol?

I have 2 12 volt batteries fully charged they were used for a electric dirt bike i tried to hook up my amp to them and the amp wont turn on i even hooked a switch up to it and flipped it on but wont work and i have the amp hooked up right to ? need help could it be the cords im using i am using some cheap skinny wire for the battrey.