2006 club car ds charging problems

[Chefcm]

i have a 2006 club car ds which I just purchased. I put 4 brand new 12 volt batteries in the car. After using the car for a while I plugged in the Charger and the charger clicked on after a few seconds and needle went to 15 amps. When I came back next morning the charger was at zero but the cart didn't fully charge. I drove it about 1/4 ,mile and then it died on me. I trouble shot as much as I could and what I figured it was the relay in the charger but to be sure I borrowed a friends charger and plugged it in to my cart. The charger turned on and the next morning same thing happened it blew my friends charger. He took his apartment and traced it that his relay was fried. I wasn't expecting to blow two chargers thinking that it was just my charger.. I had no idea my cart was blowing the Chargers so now I'm trying to figure what on my cart would blow out two chargers? I checked all the cables, wires, etc. the last charge charged the battery to 48v when I put a meter to the 1st and 4th battery. So could the issue be the OBC? I' read that the on board charging system causes problems?