Potential power source for the Nexstar mount

I had been using 3 pieces of 18650 in parallel to provide power to my Nexstar mount via the external power socket.  The internal AA battery compartment is also used as a backup source.

Last night I tried to pull out the AA battery compartment and I found it easy, it was just fixed there using double side sticky tape.  I tried to fit in my 3 pieces 18650 battery pack there and it has more space than enough, and such a modification is easily reversible too!

It even has enough space for a electrical coupler and thus no soldering required.  I'd love to find/make a replacement battery cover after the modifications.