Even though cells may exist with the same specs, it's hjighly recommended to create a battery pack from a single supplier and standardize on that. For example when I used to do professional laptop repair, I discovered the '18650' is only a size rather than a catch-all for all 12V cells, and isn't recommended to daisy-chain the various good ones together if they only share the same voltage. There's over a dozen different colors that indicate these batteries were built by various suppliers with use cases such as fast discharge rate, higher peak voltage, greater capacity, or a cost-effective battery that survives fewer discharge cycles. Creating a pack with mismatched batteries could cause the load balancer or device to operate outside of spec- don't cheap out on your power source!
