What is the voltage of a fully charged battery pack?
Lithium-Ion batteries should be balanced charged like their LiPo counterparts. Although a commercial Lithium-Ion battery pack might be balanced prior purchase and can be charged/discharged using a single connector, the individual cells' voltage can become misaligned over time and damage can be caused if they aren't balanced.
You should consult the datasheet/manufacturer and ensure there is some type BMS circuit built in.
Or you could open it up and check for yourself... (at your own risk!)