Originally Posted by rm -rf

It's best not to keep it discharged or fully charged.

Dinotte lights told me to long term store their headlight battery packs at about 7.8v. Fully charged, they are 8.4v.

I'm not sure if you can just plug in the junction box with the usb connector to the battery and charge it. It's possible it needs the shifters and derailleurs configured too. And the battery level lights work from a long press of one of the shifter buttons, anyway.

Try the battery, a connector cable, and the junction box. See if the free E-tube Project software shows a charge level when the charger is plugged into the PC's USB.