Bad short in electrical system CV25S

Bleach

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I thought I had a bad battery so I bought a new battery. I nearly cooked it. It started OK but quit after a few seconds of running. The voltage dropped quickly and the battery started smoking. Both cables were super hot. There's something shorting out. Where to start checking? I've never had anything happen like this on a car so I haven't a clue what is the problem. It doesn't seem like the starter solenoid is sticking.
There's no sparking when I first connected the battery but I got some sparks after I disconnected it. I didn't want to leave it connected after his happened fearing damaging the battery or frying any wires.
 

bertsmobile1

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Sounds very much like either the battery is in backwards or the rectifier is wired up backwards or the rectifer is defective and pumping AC back into the battery
 

Bleach

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Battery was hooked up right. The rectifier has just a plug so it can't be wired up wrong Is there a way to test the rectifier?
 

cpurvis

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If the rectifier is the culprit and enough current was flowing to make the battery smoke and the battery wires super hot, why didn't that rectifier plug melt?

I think you've got a dead short to ground, somewhere in the circuits that have BIG wires. I can only think of one--the starting circuit.
 

Bleach

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There was a suggestion in my other thread that the starter could be at fault. I'm just not all convinced since it still seems to work fine but I'm no expert. I have to figure how to test it myself.
 

bertsmobile1

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If the rectifier is the culprit and enough current was flowing to make the battery smoke and the battery wires super hot, why didn't that rectifier plug melt?

I think you've got a dead short to ground, somewhere in the circuits that have BIG wires. I can only think of one--the starting circuit.

If he has a dead short to ground then
1) there would be a big spark whenever the battery is connected or disconnected
2) the battery would go flat when the engine is not running
3) the wire on the rectifier is big enough to take the maximum current the alternator can produce + 25%

Pumping pulsed DC or AC into a battery will kill it in no time flat as will pumping in too high a voltage
If the rectifier is pushing 25 V AC ( or more ) into the battery the wires will get very hot and the plates will gas badly

Not discounting that there may be a short in the solenoid.
Or a short in the power wire to the solenoid from the battery
All are easy tested.
Disconnect the + wire at the battery and at the solenoid
Run a light jumper from the battery + to the solenoid the start the mower using a heavy jumper from the battery directly to the + on the starter, remember you need 12V to open the fuel solenoid
or
Disconnect the stator wires and run the mower
 

Bleach

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I don't think its overcharging since the voltage at the battery dropped, not increased. I did get gassing when the problem occurred the first time. I was mowing for some time after I started it, maybe 5 or 10 minutes ans then it just died. I thought it was out of gas but I had just filled it. It didn't even click when I tried restarting it. I didn't check the cables then. I hooked up the battery charger without disconnecting the cables to just jump it and it just pegged. I thought then it was a shorted battery but found otherwise this morning with a new battery.
I'll try your test method Bert next time I have a chance, maybe on Monday. I don't do any work Sundays.
 

bertsmobile1

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If the rectifier is the culprit and enough current was flowing to make the battery smoke and the battery wires super hot, why didn't that rectifier plug melt?

I think you've got a dead short to ground, somewhere in the circuits that have BIG wires. I can only think of one--the starting circuit.

Because the plug is designed to carry the full load of the alternator's output.
The alternator is not putting out any more amps than it would be so there is nothing to make the plug hot.
The plug can take 25 amps but the alternator only puts out 15 so well withing the designed capacity of the plug and for that mater the fuse.

Heat is generated by a resistance such as corrosion ( all metal oxides are resistive ) or too much current for the wire.
Neither is happening at the alternator plug, so nothing to make it hot.
 

cpurvis

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25 amps is not enough to heat up battery cables or make the battery smoke.
 

Bleach

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But a bad rectifier could reverse the charging polarity and heat up things fast. That's a easy check by simply unplugging and see what happens then. That's my next plan.
 
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