What's inside an Expedition e-bike battery?

I recently had the opportunity to tear into some Expedition Battery packs.  I needed a 72 volt battery, and with none in stock, but a good selection of identical 36V units on the shelf it was time for some creative re purposing.

The 72 Volt battery is a story for another day.  The following photos gives a good idea of the quality of these packs

This is a small pack consisting of 40 Samsung INR18650-25R cells in a 13 series 4 parallel arrangement. It includes a 30 amp battery management system that protects against over charging, over discharging, and over current, as well as short circuits.  It also balances the cells to maximize capacity.  This pack includes remote turn on wires as well.  The banana is included for size reference (with a nod to Endless Sphere)

What's under the wrap?  Lots of protective materials to keep the pack safe from physical damage.  Here we see a layer of Fiberglass card.

Under the card is a layer of high density foam.

Here the cells are exposed.  They are held together by fiberglass tape and hot glue.  The BMS circuit is visible on the Right.

Here the positive discharge wire and charging wire are visible.  Notice how they are run in a channel in the foam.

Here's where it gets interesting.  Custom cut nickel strips welded to the cells for great current carrying capacity. Note the BMS sensing wires on the top of each strip, and the fiber washers on the positive battery  tops to avoid short circuits to the battery casing.

Here you can see the BMS sense wires, cleanly laid out, and protected under a layer of foam and fiber card.

I have a sale on in stock Expedition Batteries here