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Hello:

I have owned this lawn tractor for 10 years, and never experienced a problem with it before. I was mowing a few days ago, and, after about 15 minutes, the positive battery cable caught fire. I have not had a lot of repair experience, but I feel this is something that I should be able to fix myself. However, when I attempted to remove the negative battery cable (as I know I should first), it shot sparks before I could even get it loosened. This was not just a few sparks, this was a huge poof! I have not had this happen before. I am wondering, is there another problem in the electrical system that is causing this? Also, is there danger of the battery possibly exploding when I am trying to remove it?

stepping-stone2002 said:

Hello:

I have owned this lawn tractor for 10 years, and never experienced a problem with it before. I was mowing a few days ago, and, after about 15 minutes, the positive battery cable caught fire. I have not had a lot of repair experience, but I feel this is something that I should be able to fix myself. However, when I attempted to remove the negative battery cable (as I know I should first), it shot sparks before I could even get it loosened. This was not just a few sparks, this was a huge poof! I have not had this happen before. I am wondering, is there another problem in the electrical system that is causing this? Also, is there danger of the battery possibly exploding when I am trying to remove it?

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In my 21 years of working at the dealership, I have never seen this happen. I am going to say you have a major short somewhere. Can you post some pics or even better yet, a video showing what happened. I would like to get a visual on the situation in order to try and diagnose this.

Will

Yes, a battery can explode. Lotsa sparks over the top of the battery, where flammable gases are venting, can cause the rubber casing of the battery to blow, spewing sulfuric acid. I've seen one blow 1/4 of the top open. BE CAREFUL! Safer method is disconnect ground cable from the frame - away and below battery. If you're uncomfortable with this - take to dealer/someone more experienced.
Possibility: the POS and NEG cables are both grounded to the tractor frame now. It's become a big charcoal firestarter resistor.
Maybe solenoid or starter failed so completely internally that the big POS cable is now connected to the frame.

Have fire extinguisher on hand. Had same thing happen in 79 when disconnecting ground cables first for cleaning & preparing to load test batteries in mid-range diesel truck. Both batteries caught fire & exploded, sounded like a bomb going off. An older fellow mechanic grabbed a fire extinguisher from cab of his tractor & put fire out. Thankfully no one was hurt. Replaced both batteries & good to go. Found out one of the batteries was bad, shorted out, please keep us apprised of the situation, thanks, Mark

ANd a faulty rectifier can pump AC into the battery which causes hydrogen gas to be evolved .
If the battery vent is not working then the hydrogen can build up enough pressure to blow the top off a modern battery from just the pressure build up alone.
Then you will get a spark from one of the bus bars inside the battery shorting which ignites the hydrogen and you end up with a very big bang.

If the vent is working then the hydrogen gas comes out the vent and ignites thus your battery is on fire till the hydrogen is all burned up.

The battery makers & governments have been argueing for at least 50 years about the size & position of battery vents.
Too big and the gas can burn back through the valve & ignite the trapped gas inside the battery case ( bomb ).
Too little and the case pops off or splits which will case a flash burn, usually not enough to catch the vehicle on fire but then it will pour acid out everywhere.
On trucks a similar arguement about how close to a fuel tank you can put the battery.

That is a dead short in the mowers wiring, not the battery burning.
there is enough energy in a battery to weld around 5 yards of steel.
And by the way the wires are burned then it would most likely be one of the battery cables

Thank you so much for your responses!

The cable in question may actually be one that my late husband installed years ago to operate a broom that cleaned the driveway. At this point, think I may call in a professional. I think it's too complicated to fix on my own, and I'm a little afraid of it since the battery sparked at me.

I just wanted to give an update. I had a family member who was able to help me out. As Will had said, those cables were the culprits. There were some that were hanging off the brush guard on the front of the tractor. A bolt had come loose on the guard, allowing it to move, and some of the wires had come into contact with the metal on the guard causing a short, which had traveled up the positive cable to the battery. He removed all the extra cables, replaced the battery, negative battery cable, and headlamp wiring harness. Now, it's running good as new. Thank you again for the responses!