450 battery cooked

Put a new wiring harness on my 450 last Fall, including a new single-wire alternator. Running fine since then. Lately, it's had a weird smell when running that I now realize was a battery acid smell. I'll never forget what THAT is, because it was acrid.

I was using it to pull a brush hog, and noticed that the amp meter had no reading. I lifted the seat, and put a voltmeter on it, and it was 12.72 with the engine off, same with it running. I then noticed that the two lids to the 6 cells were slightly up, and when I looked in, I could see no battery acid whatsoever. There must be some, as the 450 still started and ran without problem. The corrugated cardboard I was using to cushion the sides of the battery looked burnt, unless it was a chemical change.

I'm an electrical pinhead, and have no clue what has happened, and hope somebody can help a poor pilgrim. I don't want to throw a new battery in until I can understand this.

One thing I did was add with the re-wiring was an external resistor. If the coil has an internal resistor, would this add to my problem?

Appreciate your thoughts. Here's my wiring diagram...

Two possibilities. Either the battery failed internally and caused those cells to over charge or the alternator has failed and over charged the battery causing a battery failure. The voltage coming from the alternator should not be over 14.5 volts if it is 15 or mare the alternator is the problem. If the charging voltage is Okay then the most likely cause is a battery failure,

Put in a good battery, voltage 12.25 with the engine off, 12.16 with the engine running, (starts right up, runs strong), but still no action on the amp meter.

Getting too dark now to check anything else tonight. Wiring looks OK at the amp meter with a brief glance. I"m lost.

Sounds like your regulator in the alternator is toast. Take the alternator to your nearest parts house and have it tested. While you are there, trade it for a standard 3 wire alternator. much more dependable. wiring diagrams in the archives.

You should be seeing 14 to 14.5 volts. As suggested have the alternator checked. The alternator may have been overcharging. Hal

The battery went dry on my brothers WD45. When it blew up, it was like a 12 ga. shotgun went off in front of me. Get some water in it be for you start it up again. I got lucky.
SDE

Something wrong with the alternator or charging circuit. Voltage at battery should be at least 13 volts with engine running. If the battery is fully charged, with engine running voltage should be around 14. Engine off 12.2-12.5 volts.

Odds are overwhelmingly in favor that the alternator's internal regulator failed, overcharged the battery, and burnt itself out.

Replace the alternator and refill the battery. Keep an eye on the ammeter. After starting it should drop back to almost zero after a few minutes.

Will I have to worry about having cooked any wires or gauges?

Any best way to 'decontaminate' the battery compartment under the seat? The wire that powers the rear lamp seems OK, (it runs through the battery box), but the cloth wrapping around it falls off in shreds.

I have the alternator off, and will take it to Autozone to get tested. I'll report back.

Here's a pic of the battery. I'm surprised it gave any power at all. Don't think I'll use it again.