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Old 30-07-2010, 17:49   #1
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Batteries Boiling Over

Ok so this isn't a boat question but a has to do with my diesel tractor. This will be the second time that I have had to scrape all the rust from under the battery because it is boiling over. Last time I had to replace the radiator as well. Thinking it was a problem with the alternator/regulator I brought it in to be tested at a reputable shop. The alternator tested out fine. The shop says it is putting out 14.2 volts. I'm seeing 14.6 volts. At any RPM. So yes it is regulating but is that too high a voltage? I have let it run for maybe 30 minutes and the alternator started at 6.7 amps and now is down to 5.7 amps. Does anyone know what voltage/amperage a battery needs to get to before it boils over? Is this too high a voltage to run the tractor? It has a single lead battery. I don't know the amphours but can look it up easy if it will help.
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Old 30-07-2010, 18:05   #2
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Your battery might have a shorted cell and your meter is way off....but more likely it's the alternator. Take it and the battery to the shop for a test.
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Old 30-07-2010, 18:12   #3
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Took it to the shop and he says it is fine. I am trying to figure out why the battery is boiling over. The regulator is sensing around 14.5 volts and sending out around 5 amps to the battery. Anyone else have an idea?
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Old 30-07-2010, 18:17   #4
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14.5 volts is way too high. That is what is boiling your battery. A properly operating alternator/regulator should put out about 13.5 volts assuming that it is a basic one step regulator.

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Old 30-07-2010, 18:29   #5
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Took it to the shop and he says it is fine. I am trying to figure out why the battery is boiling over. The regulator is sensing around 14.5 volts and sending out around 5 amps to the battery. Anyone else have an idea?
I meant take both to the shop again. If the alternator is boiling the battery then it or maybe the battery is broken.
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Old 30-07-2010, 18:31   #6
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I meant take both to the shop again. If the alternator is boiling the battery then it or maybe the battery is broken.
misunderstood you. The guy at the shop said that 14.5 was OK I don't agree and there is no other shop in town. For my own information what is the reason to bring the battery?
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Old 30-07-2010, 19:04   #7
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a battery hydrometer (even the cheap ones) will tell you your cell electrolite specific gravity. that should tell you the cell condition of your battery.

The alternator should put out about 14.8 at higher amp charge rates and taper down to almost 0 amp charge and 13.8 volts or so,if the battery has good cells and a full charge.

If it ruined your last battery the alternator is highly suspect.
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Old 30-07-2010, 19:07   #8
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At 20C (68F) a typical lead-acid battery will begin gassing (boiling) at 14.4v. This voltage lowers about to around 14.2 if it is hot (30C, 80F). So 14.5 is too high except if it's near freezing.

I suggested taking the battery along to help demonstrate the problem. But you may need another shop.

There might be a problem with the battery. But your evidence suggests the alternator.
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Old 30-07-2010, 19:21   #9
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Charlie,
14.5 volts all the time is way too high....it just is. 14.2 volts is the most you should see with 13.7 volts slightly more or less being the norm after the battery is charged.

Either the voltage regulator is toast OR the voltage sensor wire leading off the regulator has some resistance giving the regulator an artificially low voltage causing the voltage regulator to overcompensate.

The regulator may or may not be built into the alternator. Usually it is. If you can't buy just a regulator then you will need to purchase a replacement alternator.

You also want to make sure all your crimps are good and your terminals are clean.
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