I did that a few years ago on my club Car Powerdrive charger and helped another member do it on a Yamaha charger.
I think the charger You are referring to is the old big box so it is definitely doable, You just need to identify the "sense" wire inside the charger.
Anyway, here is the thread:
http://www.buggiesgonewild.com/elect...e-control.html