I purchased the N2 through an online auction. The seller said he had won the speaker and had never used it. The description said that it came with the battery. I inspected the box when I went to pick it up, everything was in its packaging and I mistakenly assumed that the power cord brick was the battery. I am assuming that the battery is external and I have been trying to contact Axiom to purchase one.
Any insight would be helpful.

https://www.axiomaudio.com/n2-battery

The battery is an optional feature and maybe the seller assumed that it came with the battery.

The battery is internal.

The battery is internal.
https://bsscommerce.com/magento-2-extensions/administration.html