Step 5: Install Battery Box
The next thing to do is to decide what kind of battery box you want, measure your battery and controller, select the box, drill some holes, cut a wire opening, and install the box.
1. Decide on a box. This kit is powered by a 36V 15AH LiFePo4 battery. Instructions with the battery say do not drop, dent, or otherwise injure the battery...in other words, protect it. I decided on a hard plastic box, but later switched to metal. The instructions further recommend padding the batteries in foam.
2. Measure carefully how much room you need. The box used here is made by Buddy, 12-3/4" x 8-3/8" x 6-1/2". Two of them delivered from Amazon cost about $41. They have locking tops which is good for some security at least. The down side is extra weight of the metal.
3. Ours were mounted on rear bike racks. I took the racks off of the bikes, turned them upside down, marked the holes and drilled right through the rack(s) as needed. Then bolts were just inserted. One thing to do here is put some glue (I use Goop) on the threads since your bolts WILL otherwise work loose under vibration.
4. Cut a slot for the wires. Remember the wires you carefully dressed to the back? Cut a slot about 1 inch deep and 1/2 inch wide for the wires. I cut this slot at the top of the box using an angle grinder and moto-tool. The lid can still close over the wires, and they can run across the top of the battery to the controller.
5. Drill the controller holes. Measure and cut 2 holes for your controller just like you did for mounting on the rack. Be careful not to drill the controller!