Follow this guide to swap out the on-bike charging port for your bike that uses a Hidden Downtube Battery alongside the small parts kit from Biktrix. The parts names used in this kit will be the same as you see here
You will need the following tools to do this:
3mm Allen Key
Exacto knife/sharp blade
Hair Dryer/HeatGun/Lighter to shrink heat shrink
Remove the screw holding in the battery release knob with Phillips head screwdriver. Then remove the battery release knob.
Remove the three screws located around where the battery release knob was with a 3mm Allen key. Then remove the screws.
With the hardware removed you can remove the battery lock. Push the keyhole inwards then slide out the battery lock from the downtube cavity.