12 volts is all the same. you can buy anything from a 1.3 amp hour to a 350 pound ups backup. we installed 2400 of these in a chase bank routing center that processed 3 million dollars per second.
I like a 10 amp hour which is slightly taller than a vex battery or a 17 amp hour which most jumper boxes come with. Those work great especially the ones with a cigarette lighter accessory.
My latest is a kingcraft from aldi , which was on clearance last winter for $19 and has a usb, 2 cig lighters , 2 lighting options , a compressor , and jump starter.