a123system batt and charger

[BrianG]

From what I've seen, most "CC/CV" chargers do something like the 109, except they don't pulse. They really do CC throughout the whole charge and then when it gets to the "CV" phase. Then, it's not really CV; they continually adjust the current to keep 4.2v/cell. That's why I call this adaptive CC. :)

The Xtrema is the opposite. It is a CV charger that continually adjusts the charge voltage to push the required current in "CC" mode. In CV mode, it simply locks the voltage at 4.2v/cell. This is directly from the maker via email. When I saw what was going on via V meter and C meter, I emailed hime and he confirmed and explained it. BTW: you are correct; it is 170w.