Dead car battery

[Akragon]

There is no way to know unless you know age and real reason for why it died.
There are optical tests instruments for battery acid strength, but it don’t say anything of purity.

In a fully charged lead acid battery from your old pickup truck, with good lead plates (electrodes), the electrolyte is around 38% H2SO4 and around 62% H2Oper cell, the acidic electrolyte at this concentration of acid the specific gravity will be about 1.28 for each of the (2-volt cell) of the battery of cells.

As the battery discharges under a load the specific gravity of the acid as well as the concentration of acid changes to water as the cell discharge water from the original electrolyte and water from the chemical reactions involved.

on the discharge of the cell (6 cells in a 12volt), the electrode anodes of the pure spongy lead in the cell are converted to lead sulfate, and the cathode electrodes of lead peroxide PbO2 also convert into lead sulfate lowering acid concentration and specific gravity of the solution more towards the specific gravity of water alone.

As the cell is charged the specific gravity raises back to around 1.28
0r 37%H2SO4 62% H2O for that volume of electrolyte.

a cell fully charged will have a specific gravity of about 1.28
a cell with a 70% charge will have a specific gravity of about 1.22
a cell with a 50% charge will have a specific gravity of about 1.17
a cell with a 30% charge will have a specific gravity of about 1.12
a cell with a 10% charge will have a specific gravity of about 1.07
a totally dead cell electrolyte will just be water sp. gr. 1.00

a bad cell can develop a hard sulfate, or plates can sort out, or break lowering the sp. gr. and that cell's ability to charge, this cell will have a different specific gravity from the other 5 cells in the battery.
so even most "Dead batteries may still have a good portion of the dilute acid if those cells will still hold an electric charge at the electrodes.

So charging the old battery before recovering any acid, the better the condition of the cell the more charged the more acid in volume and concentration you could recover.

Evaporation can be used to concentrate the acidic water up to its azeotrope of 98% concentration by evaporating off water from the much less volatile sulfuric acid.

The automotive store will have a very cheap pipette with floating balls to get a good idea of specific gravity for this range, you can get a higher dollar or better tools to test (concentration of acid to water) or specific gravity and in wider ranges...

edited (Change number cells, my eye sight cannot tell 6 from9 at a black wore out old keyboard)

So... that acid is still decent... and can be refined..

 

[Akragon]

thats what i took from his/her reply as well... good to know

 

[stoneware]

Oh sorry... how do you test Sulfuric acid for purity... few drips on a paper towel?

Test acid with a hydrometer or with a Baume.

Further down in this thread you mentioned using the battery lead for smelting.

The lead is most likely alloyed.

Difference Between Lead Acid and Calcium Batteries

 

[Akragon]

Test acid with a hydrometer or with a Baume.

Further down in this thread you mentioned using the battery lead for smelting.

The lead is most likely alloyed.

Difference Between Lead Acid and Calcium Batteries

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I don't think that was me... i have no use for lead... i want the sulfuric acid

 

[jobinyt]

It's kinda like looking at muddy water. Let it settle and it looks good enough to drink, but there is no knowing what pollutants are still there. Your decision to recover/re-use that acid depends on your tolerance for unknown pollutants.

 

[D-dog]

A couple things to keep in mind.
Lead is not the only metal in car batteries.
Cadmium is added in very small quantities to many better quality batteries.
It increases the out amperage output and adds longevity to the battery.
Back in the day, you could buy Cadmium in solution to add to your battery. I used it a couple times. It was surprisingly good at restoring weak batteries. Made one battery last an extra 5 months. And that was after it failed to start the car even after being charged.

Cadmium is nasty stuff that causes cancer.
So be very careful if you mess around with old batteries.

 

[goldshark]

I have an acquaintance who rehabs batteries for a living. Not the India style of rebuilding, but a technique where he runs the battery through a desulphidizng process. Many batteries that are tested as bad, at the auto parts store, are in some state of being sulphidized, and not at the end of the useful life. I am not sure of the actual process he uses, but he is very successful in his business. If any electrolysis people on here know the process, I would really like to know it. Thanks.

 

[butcher]

maybe he is using his arc welder to de-sulfate the bad cell, in the lot or battery the electrochemical of cells.

 

[Lino1406]

I have an acquaintance who rehabs batteries for a living. Not the India style of rebuilding, but a technique where he runs the battery through a desulphidizng process. Many batteries that are tested as bad, at the auto parts store, are in some state of being sulphidized, and not at the end of the useful life. I am not sure of the actual process he uses, but he is very successful in his business. If any electrolysis people on here know the process, I would really like to know it. Thanks.

Since both electrodes are covered with lead sulfate maybe dissolving it in concentrated sulfuric acid is one possibility

 

[goldshark]

Yea, then what? Add distilled water, shake , dump, repeat? Charge first, dump acid, then proceed? Dump acid first, then charge? Add carbonate base? I have seen some videos of dumping acid, adding a carbonate ( I think ) solution, which gives voltage for a while. Many possibilities. Chemistry is not my forte.

 

[Akragon]

I have an acquaintance who rehabs batteries for a living. Not the India style of rebuilding, but a technique where he runs the battery through a desulphidizng process. Many batteries that are tested as bad, at the auto parts store, are in some state of being sulphidized, and not at the end of the useful life. I am not sure of the actual process he uses, but he is very successful in his business. If any electrolysis people on here know the process, I would really like to know it. Thanks.

I would think the reason the charge is not available anymore is because the metal plates are covered in lead... so why not just scrape off the lead and expose the original metal to the acid once again? would that not create the same environment as the original battery minus whatever is dissolved in the acid?

 

[Yggdrasil]

I would think the reason the charge is not available anymore is because the metal plates are covered in lead... so why not just scrape off the lead and expose the original metal to the acid once again? would that not create the same environment as the original battery minus whatever is dissolved in the acid?

Did you read Butchers explanation?
If not, then read it.

The problem arises when something has gone wrong by user error, adding dirty water into the battery or some kind of short and such.
New battery acid is cheap so why mess around with unknowns?

 

[Akragon]

Did you read Butchers explanation?
If not, then read it.

The problem arises when something has gone wrong by user error, adding dirty water into the battery or some kind of short and such.
New battery acid is cheap so why mess around with unknowns?

unknowns make things interesting... and sulfuric acid isn't cheap here... and hard to get unless you want to mess with drain cleaners and they're always mixed with something complicated. Said battery hasn't been touched since it was installed in my car...the point of the OP was to see if anyone knew if the strength of the acid would still be decently high. Apparently the answer is yes.. and IF i take a bit and filter it... then reduce, it will make a decent Sulfuric acid, which i want... without paying market price

 

[Yggdrasil]

unknowns make things interesting... and sulfuric acid isn't cheap here... and hard to get unless you want to mess with drain cleaners and they're always mixed with something complicated. Said battery hasn't been touched since it was installed in my car...the point of the OP was to see if anyone knew if the strength of the acid would still be decently high. Apparently the answer is yes.. and IF i take a bit and filter it... then reduce, it will make a decent Sulfuric acid, which i want... without paying market price

Well, personally I mess as little as possible with Sulfuric.
It's one of these substances that can give you really bad burns.

 

[Akragon]

Well, personally I mess as little as possible with Sulfuric.
It's one of these substances that can give you really bad burns.

right but it disolves lead...

 

[Yggdrasil]

right but it disolves lead...

Not much, for practical purposes nothing.
So far my only use for Sulfuric is to drop lead. If you want to dissolve Lead, then HCl is a better solution.
Edit for clarity.

 

[Martijn]

unknowns make things interesting... and sulfuric acid isn't cheap here... and hard to get unless you want to mess with drain cleaners and they're always mixed with something complicated. Said battery hasn't been touched since it was installed in my car...the point of the OP was to see if anyone knew if the strength of the acid would still be decently high. Apparently the answer is yes.. and IF i take a bit and filter it... then reduce, it will make a decent Sulfuric acid, which i want... without paying market price

Yes, true, but: Unknown things in Chemistry also make thing very dangerous!!

consider this: try to imagine when you have an accident with Hot Sulfuric acid, and you are in a hospital for treatment of hot sulfuric burns, what was cheaper.
Time, tools, workshop and materials is also money for most of us.
Sulfuric holds on to water very strong, you'll have to heat it to far above 100 degrees to let anything evaporate!

I buy 96% draincleaner for stripping gold plate and never (during my limited time spent on recovering with the sulfuric cell, just five kilograms of pins) had a problem. Maybe there are no additives and i'm just lucky.

Be carefull and prepared!

 

[kingwilly]

Akragon, The short answer to your question is yes, dead batteries have a decent amount of acid that can be filtered then heated to increase strength. It is even possible to get it to white fuming level. Be careful this stuff will mess you up at higher concentrations and hot. Do it outside as the fumes will ruin your day. I have done this and have a few clean litres of high concentration acid. On a side note, I do this since its almost impossible here in Aus to buy it easily or cheaply (we cant be trusted in Aus)​

 

[Yggdrasil]

right but it disolves lead...

What do you want to use the Sulfuric for?

 

[Shark]

You don’t want to reduce or concentrate sulfuric acid inside. If you do it out side you will need a cut off to the power at a distance from the heat source. 50 foot minimum. If it gets to the point you see white smoke you do not want to go near it. This smoke is such that one breath of it will reform into sulfuric acid upon contact with moisture. Think of the moisture in your lungs and sinus passages or eyes.

As for using battery acid over drain cleaners there is not much difference they are both impure acids. Be it from the additives in drain cleaners or some chemical additive to help the battery’s power or longevity. With drain cleaners the MSDS sheet will tell you what the additive is. With an old, used car battery it’s just a shot in the dark. Even if you have had the battery since it was new there is no sure way of knowing how it started out.

Best bet is buy chemically pure sulfuric acid. Second best would be a drain cleaner (with MSDS sheet) and last used battery acid.

If you try to heat sulfuric acid. Do not get the wind into your face. As well, do not have it blowing directly at your back, it will cause a swirl effect that will pull it back in your face. You want the wind blowing at a 90* angle to your body, causing it to sweep more fumes away from you. Fume hoods do a great job of protecting you over working out side.

I have heated sulfuric acid to 125F and dripped it on to dry wood. The burning effect was immediate and severe enough turn the wood black instantly about 1/8 inch deep. It was so thorough and quick it was the last time I tried to “clean up” sulfuric acid. Sometimes the cost is worth the few dollars saved. Saving your health (or life) is worth how many dollars?