This is a picture of my 4 batteries ready to be stuck in the bottom compartment of my backpack. The batteries are Panasonic LC-P127R2P. They are 7 amp hour batteries.
In this photo the batteries are zipped up in a slightly insulated lunch bag. The fit is very good so the batteries don't bounce all around.
The pack is all zipped up and ready to go with the batteries in the bottom compartment. This is the black part of the bag. There are two sets of wires. One is for the motor and the secon is from a Ni-MH battery in the sid epocket for my helmet light.