Landed in my hands, an aftermarket battery for DeWalt tools labeled 60V and 20V. From what I read, self adjust to the tool needs. 120V is also mentioned, which means extra magic to me. Anyone knows how the magic works ? Has to be one of the contacts telling which tool is plugged in...

----> https://www.burnstools.com/dewalt-flex-volt-battery
It completed charging on my 20V charger, appears happy. Another mystery for the charging process... Do they go 3 x 20V in parallel ?

 

Three 20V batteries in series produce 60V with the current the same as for 1 battery.
Three 20V batteries in parallel produce 20V and can be charged with a charger designed for a 20V battery but with three times the current as a single 20V battery.