Hi All. 25 plus years ago I had a 12V 7ah Yaesu battery that they are originally used in alarm systems for the same price of $30 at Radio Shack for powering my VHS/8mm camcorders.I got hours and hours use out of it then 45 minutes with the stock camcorder batteries.They are still available online or at Home Depot or Lowe's. .Its nice and small to handle.I still use them for my portable devices today.I use a motorcycle battery charger to charge it.
Something that size will make your audio equip run for days with out a drink "charge"from the wall outlet.just make sure there is a fuse in the line for safety.