All of the large format packs have pins for each cell, so charging with a standard balance charger is pretty easy. You can find plenty of schematics for homemade controllers online. Where they differ however, are the other pins. Some use a communication protocol like SMBUS. Some have dedicated pins for specific things like overcurrent or temperature. It varies highly from manufacturer to manufacturer.
AFAIK, all tool brands are moving to communication protocols for the packs.
[EDIT] Someone mentioned adapters. I don't believe there are adapters that support newer communicating packs (e.g. the OEM chargers won't work with the adapter). Older packs are all analog, so conversion is just a simple matter of rerouting the pins.
