[NTLK] A battery idea?

[trivialproductions]

Hi all

I was finally rebuilding my MP2100 battery pack the other day when I had an
idea (and apologies to any engineers reading this who will probably point
out the obvious flaws).

A couple of years ago, I had a replacement battery tray 3D printed and
found it had already broken by the time it had arrived.  Obviously the thin
parts were just too thin for the tolerances required.

Given the change in battery tech in the last 20 years, what would stop the
creation of, say, a 3D-printed battery pack which would be solid save for a
cutout for, say, two 3.6V lithium batteries with some appropriate
electronics to reduce the output to 6V?

As another idea, what about a reasonably flat lithium-ion battery which
could sit against the back of the case and would connect using a 3D plug-in
blank?

Cheers

Peter

PS: since rebuilding the pack with 2000mAh NiMHs, the charge level has been
really screwy, jumping up and down rapidly, and the temp reading has also
been suspiciously stable.  Could I have damaged the temp sensor, would this
affect the charge showing, and what's a good replacement if I have killed
it?