1993 Club Car V-Glide melts?

[QDMMAN]

I bought a 1993 Club Car carryall with 36v system. I took it to some land that I have that has very steep hills and the highest tab on the v-glide melted. I thought it was just old so I replaced the V-glide, wiper and contact and when I took it there again, the bolt got so hot when I got to the top of the hill that the electric motor stopped. I lifted the seat and the new V-glide was on fire and the "highest speed" bolt was cherry red. The cart had enough power getting up, but I don't know why the v-glide melts? After the first v-glide melted, I upgraded the battery cables to 4 gauge, but not the cables from the v-glide to the coils. I do not believe that the cable was loose on either v-glide on the highest contact post. Any help? I did put a lift kit on it but that too was after the first v-glide melted. The Club Car dealer doesn't know why it is doing this either. Please help if you know why it is doing this. Thanks, Jim.

P.S. I cleaned all the battery contacts, but one of the battery had the posts corroded off, so the previous owner took a medium sized hex screw and lagged it into the flat terminal part of the battery. I put it back that way after I cleaned them all. The battery is in the middle of the series of 6 batteries. Could this be the cause? It seems to work fine on flat surfaces. Just melts the v-glide on large hills.