Melted battery connection

Just melted off a battery terminal on a Trojan 31 Gel. Battery is one year old. On the forum, it looks like something that can happen, but is there any other root cause I should be looking for beside a defective battery terminal? I recently installed a R4F motor and had the controller upgraded a week ago, but it’s not a crazy draw and the batteries should be able to handle that (right?). The cart died just a few hundred feet from the house going up a slight grade at around 15mph. I did have the pedal down, but don’t we all until we get up to speed.
Anyway, I can replace the battery and cable, but just don’t want it to happen again if I can avoid it.
(ps - battery still has a full charge, cart only died because of the disconnect. All the other batteries also have a full charge and no other signs of damage, so doesn’t seem like a massive short or something. Main cables are 4 gauge, but this 13-inch interconnect seems like 6 gauge. Could that be an issue?)



How high is the regen set on the new cobtroller?

Did you update the charher pofile for gel?

No idea on regen (R4F set it). Charger profile set to gel (double checked it).
Just realized Trojan doesn’t make 31 gels anymore. Sigh.

Can you show me a pic of some of your other terminals?

Most of the time this is due to this one getting loose, corroded/dirty, bad cable crimp. When was the last time you were in and checked?

Here are some images. Honestly, I never gave them more than a passing look. I’ve had the cart for 3 months. Got it when my father-in-law passed away and have been working on it. Mother-in-law says batteries were replaced in 2023 by their local golf cart guy.
Other connections look good, but no dielectric grease. Not sure what the ‘bad’ connection looked like before the lug was melted, but if you look at the picture below, there is what looks like rust, so could be.



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R4F doesnt usually stick their neck out too far on settings.

Only asking hecause i blew up a 210ah Leoch 8V agm in my em1400 by havimg regen too high. And by blew up i mean blowed-da-fug-up… sounded like a gunshot under the seat. Top of the battery was peeled up

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Note that the sticker on the battery says the battery DOB is closer to 11/22. Maybe if the set was sitting around for a couple months and then installed in Jan 23?

there is what looks like rust, so could be.

More than just could be, but call it a for sure. Sometimes it’s a progressive thing. It may start out ok, but several runs later it degrades, heats a little, loosens up, and you get a cascade failure. The rust on the nut/bolt looks like it has been there a while. Amps go through the fastener too.

This lug looks questionable. Perhaps it is lighting, but it looks overall tarnished. That would be fine as long as the contact surface (where the lug was touching) is clean. Not just wire brushed, but flat scraped with a sharp blade shiny clean.
image

In these two connections, - the hardware and battery lug look good, but the cable ring terminal looks suspect. I bet the guy that put it together didn’t clean them.

One way to tell is to take the car for a full throttle run around the block, then stop, and give a quick tap on all connections and feel for heat. Quick tap because you might find one that will burn your fingers.

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Thanks for the feedback guys!

Guys cart caught fire on golf course due to loose terminal connection. Sparks, caught seat ablaze. Total loss.