LiIon/LiPoly Backpack not charging battery.

Hi!

I am building a guardian sword adafruit has made a tutorial on and i have reconstructed it like that exactly. It worked fine until the battery died and i wanted to charge it. The backpacks green led is turned on to indicate the battery is fully charged but it is obviously not. Any idea why it would do that? Also i am not using the exact same battery but with similar specs. Maybe the backpack does not recognize it? The green led is still on even if i disconnect the battery.

link to the tutorial: https://learn.adafruit.com/breath-of-the-wild-guardian-sword-led-3d-printed/

Thanks in advance - Jeremy

Clearly a better question for the Adafruit forum.