An even simpler method to grid charge an Insight battery pack, is shown here...
Picasa Web Albums - Jim - Battery Trick...
Take note that the electrical isolation on my Variac setup would trip the GFC garage outlet in the winter, when the car came into the garage with wet salt/snow mix on the tires. Other than this, it worked great for about two years before I broke down and built the Dabrowski charger.
Check out picture 18 for the Variac setup.
Jim.