How to add rechargeable batteries for active pickups with a USB charging port in a bass or guitar!

I was sick of buying 9v batteries for my active pickups on my bass. I would forget to unplug my instrument cable and drain a brand new set overnight at least 2-3 times a year. No more! I’ve replaced them with Li-ion 9v rechargeable batteries and added a USB charging port. I thought of buying a Fishman battery pack and just hammering it in there, but now for the price of two really good 9v batteries I have a solution that will last me years. The batteries: (4 pack) https://amzn.to/365prqX (2 pack) https://amzn.to/2Zuryly The mountable charging port: https://amzn.to/2F2tfNy