Battery question - Fiberglass RV


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Old 07-17-2021, 04:08 PM   #1
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Battery question

Battery indicator shows 13.4v on shore power. 12.6 on battery Alone. The charge indicator never shows a full charge.

Bad cell in battery?
Bad charge indicator?

Battery is 2 yea old and full of distilled water.

Thank
Mike
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Old 07-17-2021, 04:23 PM   #2
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checking a standard lead acid battery

To check that your wet lead acid battery is "good", it should read as follows using a multi-meter when fully charged: 12.6 to 12.8 volts dc AFTER resting 24 hours with NO loads and NO charging. If it doesn't hold a 12.6 to 12.8 vdc resting charge, replace it. If you want a second opinion, have an auto parts store test it.

Also there should be just enough water to cover the plates, not filled to the top.
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Old 07-17-2021, 04:39 PM   #3
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To check that your wet lead acid battery is "good", it should read as follows using a multi-meter when fully charged: 12.6 to 12.8 volts dc AFTER resting 24 hours with NO loads and NO charging. If it doesn't hold a 12.6 to 12.8 vdc resting charge, replace it. If you want a second opinion, have an auto parts store test it.



Also there should be just enough water to cover the plates, not filled to the top.


Thank You John
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Old 07-17-2021, 05:45 PM   #4
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Battery indicator shows 13.4v on shore power. 12.6 on battery Alone...
As it should. Study up...

The 12volt Side of Life (Part 1)
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Old 07-17-2021, 08:45 PM   #5
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It should be filled with sulfuric acid and distilled water to top off from "evaporation".

You can check to see if there is a bad cell by connecting the negative lead of a digital meter at the negative terminal and dipping the positive probe in each cell (acid) on each of the 6 cells and the voltage measured should be close to each other. A low voltage on one would indicate that to be the bad cell.

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Old 07-17-2021, 09:12 PM   #6
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Originally Posted by jamija View Post
Battery indicator shows 13.4v on shore power. 12.6 on battery Alone. The charge indicator never shows a full charge.

Bad cell in battery?
Bad charge indicator?

Battery is 2 yea old and full of distilled water.

Thank
Mike
Those voltages seem correct. 13.4 is a more or less typical float voltage and 12.65 is a fully charged flooded battery. Any loads on a battery that is not being charged will reduce its indicated voltage.

Maybe your indicator is set for AGM?
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Old 07-20-2021, 09:50 AM   #7
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Also there should be just enough water to cover the plates, not filled to the top.
Indeed, the cells should not be filled to the very top. Hydrogen gas bubbling out during charging will cause overflow of the battery.

However "just enough water to cover the plates" is a poor description of how the batteries should be filled.

Wet cell batteries that can be serviced all have some sort of indication of "full". On most this is an extension down into the cell with two or more slits to allow for venting. The common term is "fill to the ring" which is very easily visible, adding water until the level just barely touches the bottom of the extension. In most deep cycle batteries such as golf cart batteries, industrial lift batteries, etc, this leaves a very large amount of water above the plates, to allow for loss of water during charging.

If a battery is discharged add only enough water to cover the plates and check frequently, never allowing the plates to become exposed. AFTER the battery is fully charged, the water level should be brought up to the manufacturers full indication, which is usually that "ring" I mentioned above, though both Crown and Trojan say to fill to a point 1/8 inch (0.125") below the ring. Filling to the ring will not hurt anything however, ON A FULLY CHARGED BATTERY.

From the Trojan website, https://www.trojanbattery.com/tech-s...y-maintenance/

General Watering Instructions:

Add water, never acid, to cells (distilled water recommended)
DO NOT OVERWATER
For fully charged standard deep-cycle batteries, add water to the level of 1/8 below bottom of vent well (see diagram A below)
For fully charged Plus Series batteries, add water to the maximum water level indicator (see diagram B below)
If the batteries are discharged, only add water if the plates are exposed. Add just enough water to cover the plates, then charge the batteries. Once fully charged, add water to the proper level indicated above
After watering, secure vent caps on batteries


Diagram A


Diagram B


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Old 07-21-2021, 12:57 AM   #8
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Adding to what Charles said. When the water is just above the plates, it appears as a flat puddle. When filled up into the, so called, "ring", the water forms a meniscus. The water looks dish shaped when peering down into the fill hole. This makes it very easy to determine if it is high enough or not. The slots along the side of the ring allow gas to escape above the water level.

When servicing the batteries, look into the fill hole and add to any that appear to have a flat puddle. Stop filling when the meniscus forms. And of course, never let the water go below the top of the plates.

If you have multiple Trojan batteries, you can install a Hydrolink system to make watering easy and accurate. I had that on my Oliver with four Trojan batteries. They needed water about every four months.
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Old 07-22-2021, 02:36 PM   #9
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Adding to what Charles said. When the water is just above the plates, it appears as a flat puddle. When filled up into the, so called, "ring", the water forms a meniscus. The water looks dish shaped when peering down into the fill hole. This makes it very easy to determine if it is high enough or not. The slots along the side of the ring allow gas to escape above the water level.

When servicing the batteries, look into the fill hole and add to any that appear to have a flat puddle. Stop filling when the meniscus forms. And of course, never let the water go below the top of the plates.

If you have multiple Trojan batteries, you can install a Hydrolink system to make watering easy and accurate. I had that on my Oliver with four Trojan batteries. They needed water about every four months.
I was searching for that term, but it just would not come to mind, thanks!

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Old 07-25-2021, 07:26 AM   #10
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We have a new style battery as they last a lot longer than the old deep cycle lead acid style. The voltage is still less than shore power. Think it is the Allanson power converters 110v to 12v conversation output setting. The battery is direct non converted 12v connection.
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Old 07-28-2021, 05:59 PM   #11
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Battery indicator shows 13.4v on shore power. 12.6 on battery Alone. The charge indicator never shows a full charge.

Bad cell in battery?
Bad charge indicator?

Battery is 2 yea old and full of distilled water.

Thank
Mike
12.6 is quite low for a deep cycle battery. Probably 75% power. Id certainly take it out of the trailer, charge it fully with no loads on it and verify that voltage and then if still under 13v take it to somebody who can test it.
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Old 07-28-2021, 07:12 PM   #12
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Thank You Testing showed it needed replacement. All done new battery working as it should.

Thank You everyone
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