charged four 6500 mah 50C packs last night.

-all packs were at 7.6 volts (3.8v/cell)

-charge rate at 6.0 amps

-charge time for three packs was around 70 minutes

-charge time for the last pack was 160 min.

I will continue to monitor but just wanted to mention that the charger is a constant, the batteries are the variable here.