How do I chg 6 batteries @ the same time in my golf cart?

I assume that "chg" stands for "charge" and not "change". My electrical engineering class has uses 6 Battery Tenders (check out this link) to charge 6 batteries in an electric vehicle. You just connect each battery tender up its own battery. You don't even need to remove the batteries, just disconnect the series connection between them. The problem is, 6 chargers at $125 each is alot of money. I would check out the battery tender website for mulitple battery chargers.
oops! Battery Tender makes a 36v golf cart battery charger that might be your solution. Here it is. It's ~$400, but it looks to be what you're asking about.