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Old 07-23-2011, 09:13 PM   #1
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Alternator overcharging coach battery?

What keeps the engine alternator from overcharging the coach batteries?

Is there test to see if a battery is being overcharged?

Thanks in advance.
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Old 07-24-2011, 06:32 AM   #2
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The engine alternator has a built in voltage regulator.
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Old 07-24-2011, 06:43 AM   #3
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Quote:
Originally Posted by KyDan View Post
The engine alternator has a built in voltage regulator.
Should the built-in voltage regulator not be functioning as designed, how can the coach batteries be checked for possible over-charging?
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Old 07-24-2011, 09:29 AM   #4
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If the batteries are very warm to the touch and out-gassing (bubbling) excessively
that is an indication of over charge.
If one cell is bubbling excessively it can indicate a bad battery or
shorted cell.
IF you have to add distilled water more than once or twice a year it could
be an indication of over charge.

A digital volt meter can help as can a lead acid battery hydrometer.
Google lead acid voltage charts
and lead acid hydrometer for more info.

Voltage variation of only a few tenths of a volt can make the difference
between normal charging and over charging but voltage alone doesn't
tell the whole story.
Voltage, battery age and condition and ambient temperature all
have an effect on the readings you should get.

There is no real easy answer you have to take all the clues and decide.

What makes you think you are over charging?
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Old 07-24-2011, 09:45 AM   #5
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I guess the easiest way is to measure the engine battery voltage. That would be the same as the coach batteries. Scangauge gives that reading plus a lot more. But the biggest problem for coach batteries is battery sulfation. This happens when batteries are on coach charger (inverter) for a long time. The batteries have to be brought up to full charge by the alternator. Battery sulfation is for real, more than an alternator over charging.
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Old 07-24-2011, 10:26 AM   #6
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Quote:
Originally Posted by KyDan View Post
If the batteries are very warm to the touch and out-gassing (bubbling) excessively
that is an indication of over charge.
If one cell is bubbling excessively it can indicate a bad battery or
shorted cell.
IF you have to add distilled water more than once or twice a year it could
be an indication of over charge.

A digital volt meter can help as can a lead acid battery hydrometer.
Google lead acid voltage charts
and lead acid hydrometer for more info.

Voltage variation of only a few tenths of a volt can make the difference
between normal charging and over charging but voltage alone doesn't
tell the whole story.
Voltage, battery age and condition and ambient temperature all
have an effect on the readings you should get.

There is no real easy answer you have to take all the clues and decide.

What makes you think you are over charging?

Hi Dan,
Two of my old batteries showed classic signs of overcharging, though they could have been defective from the get-go. Two of the four batteries (four 140 Ah sealed marine run in parallel) were hot to the touch and one was bubbling. One of these bad batteries had a reading of 10.40 volts and the other would take a full charge but overnight drop to 11.30 volts, 10% of capacity.

I’m putting in four new 140 Ah sealed marine Aqua Edge batteries this week and want to “stay on top” of any developing problems, should they occur, something I didn’t do with the last batch of batteries.

The on-board generator and shore power both produce 13.55 volts for charging but the engine alternator sends a whopping 14.30 I know the converter/charger has been doing it’s job and shutting down when it senses full charge but I don’t know if the engine alternator’s regulator is allowing too much voltage, to quickly, for too long.

My batteries are on-board (inside) and even though they are sealed and not supposed to out-gas, I’m concerned they might if overcharged. I guess the only way to check is using the old fashion, tried and true method of , “If it’s overly warm to the touch, something’s not right.
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