@githerfixed - You rule! You are the champion!
My X3 light works again!

"T9 Torx driver, €6,99. CR2032 battery, €2,99. X3 light system working again instead of buying a whole new one and committing yet more waste to the disposal stream, €priceless!"

With your excellent tinkering aid, I got my X3 battery pack open, found and replaced the little battery cell, fully re-charged and tested the light. Excellent!

Thank you so much!
(If you'll contact me directly, beer money's on me via Paypal! You can find my email address trivially by searching for my full name, below)
-Jay Libove