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Old 06-03-2017, 02:14 AM   #1
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Default Clean Case of Wet Cell Batteries

I learned recently that a "dirty" outer case of wet cell batteries can create an electrical path. See pg 46 of this article.

http://www.marcorsyscom.marines.mil/...Oct%202008.pdf

I needed to clean the battery box so I removed the two 6-volt batteries. I wiped the top clean. Out of curiosity I put the voltmeter leads on the positive terminal and on the case and measured voltages from 2.5 to 4.5 volts. Obviously wiping the case clean does not adequately remove the electrical "leakage" path. I guess this is due to outgassed acid residue.

So I cleaned the case with a baking soda-water mix. I checked the potential between the positive terminal and the case and measured 0.00 volts. I don't know how much battery capacity is lost with a dirty case, but obviously the case needs to be cleaned properly and periodically.

So battery cleaning is another maintenance item that might add to the case for switching to AGMs. I assume AGMs wouldn't have this problem but I don't know that for sure.
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Old 06-03-2017, 02:29 AM   #2
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Originally Posted by peteco View Post
I learned recently that a "dirty" outer case of wet cell batteries can create an electrical path. See pg 46 of this article.

http://www.marcorsyscom.marines.mil/...Oct%202008.pdf

I needed to clean the battery box so I removed the two 6-volt batteries. I wiped the top clean. Out of curiosity I put the voltmeter leads on the positive terminal and on the case and measured voltages from 2.5 to 4.5 volts. Obviously wiping the case clean does not adequately remove the electrical "leakage" path. I guess this is due to outgassed acid residue.

So I cleaned the case with a baking soda-water mix. I checked the potential between the positive terminal and the case and measured 0.00 volts. I don't know how much battery capacity is lost with a dirty case, but obviously the case needs to be cleaned properly and periodically.

So battery cleaning is another maintenance item that might add to the case for switching to AGMs. I assume AGMs wouldn't have this problem but I don't know that for sure.
Interesting to be sure that just wiping didn't do it. Static from wiping maybe? It likely had a light acid film on it, or maybe salt if you ever are by the beach or winter weather. It would have been interesting to see if you also had a potential to the negative terminal of the same amount and if the voltage tapered as you closer to the terminal. It would only leak if it had a connection to both terminals, or the positive and ground of the vehicle, I think.

I always clean our battery tops with Windex or 409 spray, but have never measured for voltage on the case.
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Old 06-03-2017, 03:10 AM   #3
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Interesting to be sure that just wiping didn't do it. Static from wiping maybe? It likely had a light acid film on it, or maybe salt if you ever are by the beach or winter weather. It would have been interesting to see if you also had a potential to the negative terminal of the same amount and if the voltage tapered as you closer to the terminal. It would only leak if it had a connection to both terminals, or the positive and ground of the vehicle, I think.

I always clean our battery tops with Windex or 409 spray, but have never measured for voltage on the case.
I measured a similar potential from the negative terminal. I think it was the acid residue that was the main contributor.

After cleaning consider using this:

https://shop.advanceautoparts.com/p/...5023/7071019-P
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Old 06-03-2017, 03:39 AM   #4
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I always wash my batteries

I didn;t look at those link as that was taught day 1 in auto tech.

dirt and moisture on the casing of a battery will allow electrons to flow between the poles

eventually draining the battery

mike
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Old 06-03-2017, 12:00 PM   #5
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I always wash my batteries

I didn;t look at those link as that was taught day 1 in auto tech.

dirt and moisture on the casing of a battery will allow electrons to flow between the poles

eventually draining the battery

mike
How often should the battery be washed?
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Old 06-03-2017, 03:42 PM   #6
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anytime you are in there, wash it.

depends on how dirty is gets- esp exposure to northern salt slush spray- salt makes more conductive.

I look at my battery everytime under the hood to check oil or fill the wiper juice etc.
and for my coach battery I am checking the level of the electrolyte a few times a year

or on wash day when I have a soapy sponge in my hand

mike
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Old 06-03-2017, 04:06 PM   #7
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I used to see the old timers in local garages use an oily rag at every oil change to wipe the top of the batteries down. They claimed the oil would help reduce the conductivity (maybe for me), but also make it so the next time everything would wipe off clean because of the old oil underneath (more likely).
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Old 06-03-2017, 04:24 PM   #8
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oh no!
oil traps and holds dirt

clean and dry

Mike
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Old 06-03-2017, 04:42 PM   #9
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oh no!
oil traps and holds dirt

clean and dry

Mike
I think the logic was that was a good thing, as the oil would make the dirt non conductive and also absorb the oil mist which was much worse on the old batteries. Similar to the other thing that is still done, which is totally covering the battery connections with grease.

Starting batteries these days are pretty much all calcium lead models and use very little water, so not really a problem under the hood anymore. Even the marine "deep cycle" Costco battery, gp 27, that I use for a starting battery in the van, doesn't use any water and never messes up the top of the battery like out coach deep cycle wet cells did.
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Old 06-03-2017, 09:46 PM   #10
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Just checked my Toyota Camry battery that is 8 years old and working fine. I do put it on a BatteryMinder occasionally. I got about 2 volts between the positive terminal and the label on top. There rest of the battery top had very low voltage, but not zero. The top was fairly clean. So I should use a battery cleaner/neutralizer on the case. I may pull the label off as it seem to be holding some outgassed acid in it.
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