All of the lithium batteries commonly used for ice fishing state that reduced performance and life expectancy can be expected when not charged with a lithium specific charger. I have no clue what is different about these chargers but it seems that there may be something.

Most of the batteries have a built in battery management system that will cut output power when the battery reaches a set voltage. The bms will also cut charger input when the battery has reached a set voltage

Mat Peirce
1.25 acre southeast Iowa pond
LMB, BG, YP, WE, HSB, RES, BCP