Positive Battery Cable Melted

I would be investigating before installing new battery, wires, etc. to make certain nothing else is wrong in the circuit.

I'd also charge the battery and have it tested to verify it is bad.

I'm glad you didn't have a fire.

I doubt it would be the starter. Once you get it back together, verifying the charging system would be a good idea.

I think you should check all the wiring for any type of damage. The wire was hot due to a short most likely.

Replace the cable and as stated before have the battery load tested.

If the trips to the ranch are that infrequent I would remove the battery and bring it home. Place it on the charger the night before you go. Might keep someone from stealing the tractor.

You state "trickle charger for 10 months". There is a difference between a trickle charger and a battery maintainer, but as BigG suggested, I'd remove the battery and take it home!

You may also want to check your alternator to see how much it's putting out.

North Idaho Wolfman said:

200mph,
I pretty sure that it going to be hard to charge and test it with the tremial removed from the battery.

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Where is your ingenuity? Just heat it back up and stick it together. You can do that with lead you know.

I misread that it was the battery terminal that melted. I was thinking it was the wire end terminal that clamps onto the battery that melted.

Sounds like the starter($$$) shorted out or if you're lucky the starter solenoid(cheaper). That would explain the huge current draw. You're lucky tractor didn't catch on fire. Odds are good you'll need a new battery as they don't like long, massive discharges. Get a proper molded battery cable NOT a homemade one. A trickle charger works like having a water tap on a little bit.OK if you're around BUT eventually the bucket overflows and you'll have a mess..10 months would make a BIG mess! A 'maintainer' style charger will AUTOMATICALLY shut off when the battery is full. If you don't already have one, get a wiring diagram for your tractor. Also look carefully where the cable goes, maybe it rubbed onto something or ,arrgh, MICE chewed the tasty soy plastic off it. Take pictures BEFORE you start removing 'stuff'. it'll hyelp in putting things back properly. Also use correct METRIC tools, no sense rounding off a nut or two an dmaking the job harder.....BTDT..

Back in the 60's I had a battery on on IHC 300 utility tractor explode while attempting to start engine.

The battery on IHC 300 is located between operators knees when one is sitting in the tractor seat. Now that will give one a "wake up call"!!!!

I agree tailbent needs a maintainer type not trickle charger for extended battery charging.

The fact that the engine lost power in a B7500 with an all Mechanical fuel system would indicate that either the starter or dynamo was causing a severe mechanical drag. Could be there is problems with both. If the Dynamo was burning up it could provide enough drag to slow the engine.

I don't and have never had a battery maintainer of any kind on my tractors. They sit in a barn with no electrical service what so ever and it gets mighty cold here (12 degrees today) and never been an issue.

First off, I use the largest CCA batter than will fit in the space allowed for the battery, in my case a Group 31 1100 CCA rated. I go by physical dimensions not recommended replacement size.

Secondly, I never short run the tractors, I always make sure they are run long enough to insure the battery is totally 'topped up' before I shut them down.

Thirdly and mist importantly, I break the circuit and isolate the starting battery with a 'Master Disconnect' switch placed on the negative battery terminal. I 'open' that switch immediately after shutting down the tractor(s).

A flooded cell storage battery in good serviceable condition, properly charged, only looses about 2-3% of it's total charge per month so there has never been any reason for an external charger on my batteries, even if the tractor(s) sit all winter (4 months), come spring I open the hood, close the switch and they start right up. There is no parasitic draws or any other discharge when the battery is isolated. none, nada.

Of course I use quality batteries (Interstate), not some cheapo Wallyworld junk and I don't run them forever, a flooded cell battery, the expected lifetime is 5 years. I know people run them 10 years but in reality, 5 is the projected lifetime. I load test at 5 and if they are iffy, I replace them.

Finally, it's a myth that cold temps destroy a flooded cell starting battery. That is a falsehood. It's heat that destroys a battery. The reason why batteries fail in a cold snap is because they were already shot but the cold start requires more amperage than the shot jar is capable of producing.

If you feel you must use a trickle charger, use a microprocessor controlled maintainer, not a tickle charger. A trickle charger will eventually cook a flooded cell battery, boiling all the distilled water out and leaving concentrated acid behind and destroying the battery.

I don't and never have. Mine start right up, no issue.

I'd have thought there was a fuse between the alternator and the battery. If not then yes, a shorted alt WILL kill the battery and wires.

Rodents

Before I put the battery back in the tractor I would make sure rodents have not chewed up a wire harness and shorted something to ground. If the tractor started fine and you did not hear the starter dragging the engine, this would be my guess.

Thirdly and mist importantly, I break the circuit and isolate the starting battery with a 'Master Disconnect' switch placed on the negative battery terminal. I 'open' that switch immediately after shutting down the tractor(s).

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This. You can even get keyed switches for that extra level of theft protection too.

My bet is the starter stuck engaged with the flywheel.

A starter motor will generate juice when spun faster than it would under battery power. Typically, the toggle point is about 700 rpm (engine speed).
Once the engine starts and revs build, the force of the engines' faster rpm is supposed to 'encourage' the Bendix to disengage the starter pinion from the flywheel. If the Bendix does not work (is stuck, very common in a machine that sits for extended periods) the starter motor is turned very fast.
As much current as a starter draws on start, it can generate when spun at engine operating speed. Your cables and battery are intended to carry this kind of current for brief (10-15 second) periods.

I think you are very lucky the battery did not explode.

William1 said:

My bet is the starter stuck engaged with the flywheel.

A starter motor will generate juice when spun faster than it would under battery power. Typically, the toggle point is about 700 rpm (engine speed).
Once the engine starts and revs build, the force of the engines' faster rpm is supposed to 'encourage' the Bendix to disengage the starter pinion from the flywheel. If the Bendix does not work (is stuck, very common in a machine that sits for extended periods) the starter motor is turned very fast.
As much current as a starter draws on start, it can generate when spun at engine operating speed. Your cables and battery are intended to carry this kind of current for brief (10-15 second) periods.

I think you are very lucky the battery did not explode.

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Great post.

North Idaho Wolfman said:

Good theory, but very unlikely.

This could only happen if the solenoid was stuck, otherwise the starter to battery connection is cut when you cut power feeding the solenoid.
So no backfeed could happen even if the starter did manage to get stuck in the engaged position.

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I agree. This is why I said that I doubt it was the starter. But, who knows until they get it back together and do some testing.

North Idaho Wolfman said:

Good theory, but very unlikely.

This could only happen if the solenoid was stuck, otherwise the starter to battery connection is cut when you cut power feeding the solenoid.
So no backfeed could happen even if the starter did manage to get stuck in the engaged position.

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Yes, interesting theory. But what if the starter solenoid stuck closed AND the starter also stuck in the engaged position? Yes, unlikely, but stranger things probably have happened.

The OP said: "After a few minutes I noticed the tractor slowed and seemed to lose power. I stopped dragging, the engine came back up to speed. I did this three times, and then noticed smoke coming from the engine compartment. I immediately turned it off."

The diesel does not require electric voltage to run after started. So what would cause it to lose power/engine speed after it is running? Voltage dropping to the fuel shut off solenoid? But if the issue was caused by the starter generating excessive voltage, back into the battery, the fuel solenoid would not experience under voltage.

My bet is the battery itself failed internally. It probably generated enough heat internally as the result to melt itself inside, so the terminal pulled out easily. The melted insulation on the terminal wire was probably due to heat generated inside the battery.

What does not add up is why the tractor would lose power. Granted as the battery failed, if that is what happened, the output voltage which feeds the fuel shutoff solenoid would likely have dropped.

BUT why would the situation cure itself when the working load was removed from the tractor?

I don't know about you guys, but in the old days it was not uncommon to run a battery down to nothing trying to start the junkers we used to drive. Never saw a battery melt doing that... So I am guessing that either the battery failed internally, OR it was getting excessive energy input from somewhere, which only could have been supplied by the starter motor generating.

edit: I would put my money on the battery failing internally, but when I bet I always lose...