Trying to figure out what issue is with Milwakee M18 XC6 High Output Lithium battery pack. Battery will charge by "jumping" method off another M18 battery, but when I put it on charger, it will flash "green - red" indicating not charging. Voltage is steady at 19.31-19.32 with "3 bars" lit on batter level indicator. Trying to figure out what is allowing "jump" charging and not "factory charger" charging. Nothing appears fried on board.

 

According to this https://www.reddit.com/r/MilwaukeeTool/comments/108d3j9/m18_fuel_battery_protocol there is some communication going on between the charger and the battery. Perhaps there is an issue there that is preventing the charger from recognizing the battery