H2SO4 to battery acid

I'm going to try to rebuild one cell in my forklift battery...

I have sulfuric acid 60 degree Baum. Almost pure stuff. How much do I let it down to make battery acid? I don't have titration equipment, any way to check its the right strength?

Also, IIRC, you always add water to concentrated acid, not the other way, right?

Karl

Reply to
Karl Townsend
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"Do what you 'aughter, always ADD THE ACID TO THE WATER"

Beaten into me as a child in chemistry lessons when they taught useful things at school

(The theory behind this is simple: the dilution of acids is exothermic, ie it gives off heat, so start will a large mass of cool water to absorb a relatively small amount of heat from small amounts of acid, this way the water doesn't boil and spit at you)

AWEM

Reply to
Andrew Mawson

Also battery acid is very inexpensive at the auto parts store. I got

5gal for like $15 for my anodizing line. Don't waste the good stuff, just go spend a few dollars for the pre mix and save the pure for something worthy of it.

Pete C.

Reply to
Pete C.

Acid to water. I was told that the Sulphuric has such an affinity for water it will jump towards it, that and considerable heat may be liberated causing local boiling with potential consequent splashing.

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Reply to
David Billington

I'm pretty sure you've got that the wrong way round.

Chris

Reply to
Christopher Tidy

If its a big deal, I'll do just that. But, I've got two 5 gal carboys of the pure stuff that have been sitting around for more than ten years with no use. If soembody knows how much to let it down, it should only take a few minutes.

Karl

Reply to
Karl Townsend

and if it does boil, you'll be lifting a bunch of relatively dilute acid solution out of the reaction vessel and onto you, instead of _really_ _concentrated_ stuff.

Come to think of it, wear those funny goggles and an apron -- maybe a face shield, too. Remember that evolution rewards those who don't let their balls get burnt off.

Reply to
Tim Wescott

Yup always add acid to the water.... Heat is created and will boil the water if the water is dripped into the acid.

From moy old high school science teacher... do what you ought to put the acid in the water, ( my addition) or be a bastaad and put the water in the acid.

I would get a battery hydrometer and use that to test the concentration. the specific gravity will vary depending on the battery mfgr. when you get a new battery with the acid separate, the way aircraft batterys usually come. You want the hydrometer to read a full changed condition or have the float at the highest point out of the liquid.

State of Charge Specific Gravity Voltage 12V 6V

100% 1.265 12.7 6.3 *75% 1.225 12.4 6.2 50% 1.190 12.2 6.1 25% 1.155 12.0 6.0 Discharged 1.120 11.9 6.0

You could take a small measured amount of distilled water and start adding a measured amount of acid to it until you get a full charge reading on the hydrometer. Then extrapolate and mix up enough for your battery.

John

Reply to
john

NO!!!!. Always add acid to water, and measure acid strength by measuring Specific Gravity. You want about 1.25 to 1.26, depending on the battery.

Reply to
clare at snyder.on.ca

And add the acid slowly with gentle mixing. Depending on circumstances, enough heat can be liberated to soften a plastic bottle so watch out for that possibility, too.

Mike

Reply to
Mike Henry

The pure sulfuric we buy for the lab is 98%. I'm not familiar with the Baume system, but that and Google may give you a start on dilution ratios.

Mike

Reply to
Mike Henry

what do ya mean by rebuilding?????? How old is the battery? Is it sulfated? Does it open under a load? I repair forklift batteries at work and was just wondering. May be that buying a used cell would be your best bet.

Reply to
not today

That's backwards as others mentioned. I was taught

AAA

Always Add Acid.

Reply to
Cydrome Leader

You mean Baume. It's a specific gravity measure, not a molar concentration. Get a hydrometer and dilute with that to the target specific gravity.

Reply to
Richard J Kinch

Oh, and to convert heavy degrees Baume ("Be") to SG:

SG = 145/(145-Be)

So 60 deg Be = 1.706 SG.

Dilution to battery acid SG left as an exercise for the 5th graders.

Reply to
Richard J Kinch

Why do you do that, Dr. Kinch? You have the knowledge and education to directly answer Karl's question, why don't you just do that rather than present an exercise?

Reply to
Don Foreman

Baume relates to specific gravity, the formula is

Baume :== 145 - (145/sp. gr.)

66 Baume = Sp. Gr. 1.8354 = 93.19 percent H2SO4 by wt. 60 Baume = Sp. Gr. 1.7059 = 77.67 percent H2SO4 by wt. 31 Baume = Sp. Gr. 1.2609 = 35.93 percent H2SO4 by wt.

(all this from tabulations in my trusty Handbook of Chemistry and Physics)

The 31 Baume concentration is correct for a fully-charged lead-acid battery.

Roughly, to a pound of your acid, add X pounds of distilled water to get

0.3593 = (.7767 )/(X + (1-.7767))

which is the correct target dilution with X = 1.94

All this can be checked by measuring the specific gravity of the acid after dilution. Or during, if you just want to mix/measure/remix.

Reply to
whit3rd

Another tip to the original poster, or anyone else that is adding acid to water:

The size of the forklift battery will mean a large volume of acid has to be made up, so do the dilution over a period of time. Allow a few minutes for the mixture to even out in temperature. You can see the different liquids mixing and a distortion layer that is the mixing acid, water and different temperature zones.

As a student we were making up a bright acid dip for cleaning metal, and we were mixing up about 2 litres of water, 2 litres of sulphuric acid and 2 litres of nitric acid and pouring the acid into the large glass dish half full of water caused the heating mixture to heat quicker than the glass dish which proceeded to crack around the bottom edge and we all watched it split and allow all the acid mixture to run down the side of the wooden box we were working over and onto the ground. If we had allowed ten minutes halfway through adding the acid, for the temperature to level out we wouldn't have made the mess. It would be a good idea to do this sort of work outside, as the acid will make a mess of concrete or whatever floor you have inside your workshop. Luckily we did this outside on the lawn, and although it killed a bit of grass, the spilt acid was neutralised by the soil reactions......

Hope this helps, Peter

Reply to
Bushy Pete

I've heard there's a new TV show about what a 5th grader can do that I can't, I guess I'll have to start watching it.

karl

Reply to
Karl Townsend

...

BINGO

Many thanks, I'll get a battery SG tester and go to work.

My forklift battery can be disassembled, one cell is obviously very bad. I'll try cleaning and regenerating it per the instructions in the FAQ link that Gunner just posted.

Karl

Reply to
Karl Townsend

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