WTH happened to my battery?

[Tacosquisher]

So I've had my cart for a little over a month now. (2002 txt 36v). Just received my new alltrax sr48500 controller, solenoid, f&r switch and cable combo from Scottie B and installed it all yesterday and it works great btw.

Anyway I noticed my battery on the positive terminal that comes off the solenoid; the post was bent a little bit and it seemed as if the battery was puffed up a bit under the terminal. Also apparently one of the wires was getting so hot that it was melting into the plastic on the battery. When I was changing the controller/solenoid the connections weren't terrible on the solenoid itself. No corrosion and seemed to be snug. What I'm trying to ask is what would make my battery do this?

[LukeL]

Heat has melted the battery terminal and battery. It’s usually caused by a bad cable and a bad connection. There can be corrosion making resistance inside the cable, even though you can’t see it. (That can happen really fast, BTW) I suspect that’s the case by your picture. What gauge are those cables?

Most would recommend 2 AWG with a 500 amp controller.

[Tacosquisher]

With my kit I got the all new 2ga cables. Originally I Believe from solenoid/controller to the batteries and motor were #4 I believe. But between all batteries was 1/0 which I thought was kinda weird since they were mismatched but whatever lol.
They're all the same now but I don't want to ruin the lugs on the new cables by putting them on this crappy battery. I want to upgrade soon to 48v but not really trying to fork out another grand right away but also don't want to do permanent damage or get left on the side of the road.

I already feel like I get maybe an hour ride out of it before it feels sluggish so I'm assuming it's this one battery dragging the rest down. I have a multimeter and everything but not a load tester so it's hard to see how many are bad

[Doubles Shooter]

Let the cart be the load tester. Just put the multimeter on each battery one at a time and record the voltage on each while under a load. Also total pack voltage. Start with a fully charged pack.

[Tacosquisher]

Ok I'll check it out today.
So if one or 2 batteries are bad should I replace the whole set or just a few? I feel like long term would benefit from changing all of them now

[JohnnieB]

In addition to the bad cable, or bad connection, or corrosion, over-tightening the nuts on the battery studs can also cause melting.

The studs are simply stainless steel bolts with the hex head embedded in the lead battery post. Lead is a very soft and malleable metal, so it doesn't take much fore to twist the hex head in the post and when that happens only the six points are in contact with the post while there are now air gaps between the post and the six flats, so the contact area is only a very small fraction of what the design intended.

Specs on stud type battery terminals is 95 to 105 INCH/Pounds of torque, which translates to 7.9 to 8.8 ft/lb

[ThreeCW]

The copper lug connector shown in your photo is too large for the 5/16” battery stud. A properly sized 5/16” lug will provide better contact on the lead post ... better contact results in less resistance and ultimately less heat generation.

[Notso ezgo]

Is the black lead the one that connects to charger port? I replaced my charger port that included connector and wires. Also look underneath your connector. I had the same thing happen last week with a battery cable. The cable and battery terminal were quite dirty. Plus the rubber casing around cable had frayed and exposed internal wire. It sparked and melted my post just like yours.

Edit: I reread OP and looks like you stated wire goes to solenoid.

[cdressel]

Originally Posted by ThreeCW

The copper lug connector shown in your photo is too large for the 5/16” battery stud. A properly sized 5/16” lug will provide better contact on the lead post ... better contact results in less resistance and ultimately less heat generation.

It looks to me like there's corrosion inside the copper lug and between the copper conductors. Those lugs aren't crimped very well and they aren't soldered and are open to corrosion.
Chuck

[Tacosquisher]

Yes the cable that is shown in the picture connecting to the other battery is one of the old ones that has since been changed. When I went and changed everything I used a wire brush on the battery terminal and some fine grit sand paper do try and clean it up even better. After that I put on some Noalox and put it back together.
I do need to put new lugs on the charger port, I was kinda hoping they would make it until I got a new charger when I upgraded the batteries but I'll change them out this weekend.
Mostly what I'm wondering is what made the battery puff up like that to make the terminal be crooked? I just would hate to spend a grand on a set of new batteries only to come across the same issue.