Contaminated electrolyte in lead acid battery

AfdhalAtiffTan

Joined Nov 20, 2010
120
Unless the battery is fully charged you don't want to add electrolyte since you don't know how much acid to add. Better to fully discharge the battery so the electrolyte is basically water and then flush the battery with water. Then fill it with distilled water and fully charge the battery.
That method might work best on new battery.
On old battery, every single cell is getting harder to charge as the acid concentration rises. This is due to the sulfate crystal harden with time.

In other words, the more concentrated the acid is, the more harder it is for cell to get charged. But, higher concentration means better discharge performance, with better efficiency as the ohmic losses minimizes.

Charging cells with high acid concentration requires special procedure, such as by using pulse charger, etc. Not to mention the vulnerability of the active electrodes getting corroded.

For recovery purposes, I would suggest to drain all of the electrolyte, refill it with distilled water, charge it with constant current source (voltage might gets higher and so does temperature), this is to help the hardened sulfate crystal to return back to the electrolyte, repeat for 2-3 cycles.
Now, the electrode suppose to be free from the crystal.

Refill it with fresh acid electrolyte, reform the plates, it suppose to perform better now.


All of the text above is based on my experiments, with no scientific evident to backup the claim.
However, I stand to be corrected. :)
 

Thread Starter

thomasplam

Joined Nov 14, 2013
8
For recovery purposes, I would suggest to drain all of the electrolyte, refill it with distilled water, charge it with constant current source (voltage might gets higher and so does temperature), this is to help the hardened sulfate crystal to return back to the electrolyte, repeat for 2-3 cycles.
You mean 2-3 times have to flush the electrolyte charge it with constant current:confused:

Refill it with fresh acid electrolyte, reform the plates, it suppose to perform better now.
I doubt the availability of fresh acid electrolyte (mixed already) where i live.Any alternative??

Thanks,
Thomas.
 

Kermit2

Joined Feb 5, 2010
4,162
There is also the possibility of a shorted cell. From the voltage readings you give I say it is highly likely.

Load the battery with a lamp and read the voltage during the discharge. If it is 12.3 volts or lower then you have a shorted cell.
 

MikeML

Joined Oct 2, 2009
5,444
There is also the possibility of a shorted cell. From the voltage readings you give I say it is highly likely.

Load the battery with a lamp and read the voltage during the discharge. If it is 12.3 volts or lower then you have a shorted cell.
If a cell is shorted, when loaded with a current of a few amps, the battery voltage would drop to less than 10.5V (5cellsx2.1V/cell). The resting voltage of a charged lead acid battery is 12.6V (6cellsx2.1V/cell).
 

Kermit2

Joined Feb 5, 2010
4,162
If the battery has been overcharged, which is likely, even with a shorted cell voltage can remain above 12 volts during discharge for a short time. He stated it was a 70 ah unit, so it may not drop below 11 volts for a short load test of just a few minutes.
 

ian field

Joined Oct 27, 2012
6,536
You mean 2-3 times have to flush the electrolyte charge it with constant current:confused:
.
In theory at least - *PURE* distilled water is non-conductive, in practice a well used battery will have sufficient contaminants to get some current flowing.

By the time a constant current at 1/3 the Ah capacity can force a terminal voltage of, say 20V or more - you can probably tip it out and refill with the correct SG electrolyte.

But is it worth all that effort to bodge up an old battery that might let you down in the middle of nowhere!

A tow truck will probably cost you more than a new battery, and you'll still have the same problem when you get home.
 

GopherT

Joined Nov 23, 2012
8,009
I just have the feeling that the OP has more time and money than normal folk and he will figure out a way to rinse out his battery and refill it. He will view success as a battery that holds voltage - no matter if the cost of materials and time are well above a replacement battery.

I'm done with this one.
 

ian field

Joined Oct 27, 2012
6,536
I just have the feeling that the OP has more time and money than normal folk and he will figure out a way to rinse out his battery and refill it. He will view success as a battery that holds voltage - no matter if the cost of materials and time are well above a replacement battery.

I'm done with this one.
I only did stuff like that when I was really skint and couldn't afford a new battery - I soon learned that its a waste of time and can result in at least severe inconvenience.
 

wayneh

Joined Sep 9, 2010
17,496
Zero volts
Maybe it's worth clarifying the S.G. and concentration data I gave earlier. Those values were for a fully charged battery and a normally discharged battery, i.e. not for a fully discharged (to zero volts, abused) battery. A battery will keep pushing electrons until the reactants are gone, but that's way beyond normal operation.
 

Thread Starter

thomasplam

Joined Nov 14, 2013
8
Hi Guys,

I really appreciate all the help and patience from your side. I really had fun playing with the battery, which was a new stuff for me. I have learned a lot of things. I will continue it a little bit further, just for the sake of learning.Once again thank you very much guys.

Thanks & Regards,
Thomas.
 
Hello everyone, just joined tonight after finding this thread online about Contaminated Battery Acid. I have a similar issue, but from a different cause, and would really appreciate expert advice and figured the people who helped in this thread might be just the ones to hear my issue.

I have an Exide 850 CCA 12 Volt lead acid battery that was working fine until an overzealous maintenance technician decided to give me more than my money's worth of battery terminal contact cleaner. He sprayed so much in fact that the whole top of the battery looked like it had boiled over since it was visibly wet inside both indented plastic covers that plug the 3 and 3 cell fill holes, respectively. The way this battery is designed, there are 2 overflows, one in each indentation, and should the battery over pressure, the acid would bubble out through the holes and drip down the side of the battery. As the battery cools, air pressure can equalize by letting air into these same two vents, as I understand it.

It was two weeks ago in warm weather of about 80 degrees F that this happened, and when I noticed it, I just blotted off the wet on top, but did not see a way to get the contact cleaner overspray that seeped down in between the indentations and the fill covers so I did not clean it. The battery worked fine and I forgot about the mess. About two nights ago, it got down around 42 degrees F and I went to start the vehicle, and it would not crank. The voltage read 12.0 so I used a booster pack, and got it started. Next morning, the power locks would not even work, and the voltage read 10.65 volts. I now am wondering if the contact cleaner got siphoned into the battery when the weather got colder, just like when a gas can compacts when you fill it in warm and then leave it in cold. I don't know the chemical used as a terminal cleaner, but I would assume that if it got mixed with the sulphuric acid it would not be good.

One person said I might have had a cell failure, but if so, it would have been 10.65 volts the first night when it would not crank then and not 12.0? I think that since it got even colder overnight, by morning as the battery cooled it may have sucked in even more contamination and truly killed the electrolyte. If the vents let out overpressure, then when the battery gets cold, it must equalize by letting air back in, and in my case, dragging in the extra contact cleaner fluid under the fill hole covers. Should I go out and buy a hydrometer and talk to a chemistry professor friend about how to test the acid, or do you guys have some advice? By the way this is academic for me; I am not trying to fix the battery, but I want to determine if this failure could have been caused by aforementioned mishandling by service people, and have already discussed this matter with the shop owner who is as curious as I am as to why the battery failed. I already bought a new battery and just need to figure this out as a fellow engineer. Thank you for your ideas.
 
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