Reconditioning Pb, losing track of MgSO4 -- or it worked *too* well???

I have a flooded lead-acid battery I've been working on for a bit that was left idle *way* too long. Two cells were clearly bad -- I suspected shorting in one and sulfation in the other, but was guessing the shorted one likely suffered some sulfation as well from the look of it. So I poured off most of the electrolyte from those two cells (letting any particulate gunk settle and pouring off the cleanest of it for possible reuse), distilled water rinse 2-3 times to clear out some of the remaining gunk, then made a saturated Epsom salt solution, poured it in both cells, and charged overnight. Both cells showed remarkable improvement.

Here's where I screwed up, and where the question comes in: While the portion of the original electrolyte I preserved was pretty doggone clear, and the pH was still well in the range where I'd eyeball expect it to be usable, I wasn't 100% sure I should reuse it. So, I tried it out on only one of the two cells. That ended up being the heart of the problem, as I'll get to... apologies for the next overexplained bit, because I just *don't know* why I'm seeing what I'm seeing, so I don't know which details are relevant and which aren't. Apologies in advance for the super long brain dump.

So, I closed off one cell (with the MgSO4 mixture still in it). Dumped the solution from the other cell, rinsed again with distilled water twice (leaving the water in for a couple of hours one of those times before dumping it, but I didn't charge the battery during that time -- it was close to as fully charged as it could get at the time anyway, as this was right after the overnight charge), and then filled that one cell with the recovered electrolyte.

Charged it for 4-6 hours, rested it for 2, cell had dropped under 2V. (1.6, if I recall.) So I jostled the thing around a bit to reduce any stratification I was seeing from possible leftover H2O, equilibrium-charged it to try for an increase in voltage, swapped a bit of electrolyte with a bit from one of the battery's good cells -- what can I say, I was (needlessly) worried and getting a bit desperate. I mistakenly thought getting that cell up to snuff would take 4-6 hours, when it ended up taking over a day.

Eventually, the cell works fine. (Which I guess probably comes as little surprise to most here.) A day's gone by. I've slept. I give it a nice long charge, pop all the cells again, do voltage and specific gravity testing just to see if I should fix up any other cells.

...it is at this point that I realize that I don't remember which of the two cells I was working on had the MgSO4 solution removed and which still had it in it. :fail: Dumb, dumb rookie mistake. I even told myself beforehand that I should mark the cells somehow, and my brain just shook off the suggestion. "It's only two cells, for 4-6 hours; you won't *possibly* forget in that short a time..."

Like I said, I'd only saved the cleanest, clearest portion of electrolyte for reuse. And, curse my ninja solution-making skills laughing::shakehead), my saturated MgSO4 solution had come out perfectly crystal clear. So I couldn't tell the difference by looking.

So, my college-chemistry brain says, "well, MgSO4 isn't going to turn acidic with electrolysis -- the water would electrolyze before the MgSO4 did, so I should just have more concentrated MgSO4 solution, if possible at whatever heat the stuff was running, plus maybe some precipitate. So if I just test the pH of the two cells I should be able to tell which is which."

My college-chemistry brain failed me. Because *both* cells were at or right around (limitation of my test strips -- the cheapo pH meter I had wasn't cooperating) a pH of 1, which is what I'd expect of battery acid.

I secondarily want to know what was wrong with my line of reasoning about the pH of the MgSO4 (as clearly *something* was wrong), but primarily want any clever ideas you guys may have about how to tell which cell still has the MgSO4. Thought maybe a ppm tester, but my tester freaks out at even a 1:400 dilution (in distilled H2O) of both cells' electrolyte (haven't tried weaker, and not sure if it's failing to test because of a too-high ppm count or the cheap tester not liking highly acidic solutions ). Acidity at a 1:400 dilution was also nearly indistinguishable as far as my test strips went, both seemingly hovering between 2 and 3. I was thinking perhaps take a small sample of both, mix in one of the myriad of various household salts and seeing if one or the other gives me a precipitate of an Mg salt, but hadn't settled on which to use so I haven't tried that yet.

Am I barking up the right tree? Or is there another cleverer, simpler way to test this that I simply haven't come up with? I appreciate any help, y'all -- I'm *stumped*.

Aside: apparently I can't edit my posts yet, but the "works too well" part of the title is in reference to the fact that I seem to have "magically" ended up with HSO4 in a cell that used to just have Epsom salts - or some other strong acid, I guess; not sure how that would've happened either way.

Epsom salt is a very short term solution. There is a reason it is NOT part of normal electrolyte as the salt deteriorates rapidly over time.

My advice is to stop playing with trash if your time is important to you, and avoid scams that try to "revive" such trash. Unfortunately there are a LOT of people trying to make you part with your $$ to play with trash.

Some of my favorites from the turn of the century onwards - how about putting an aspirin inside each cell? NO.

Don't waste your time and energy. You'll save money by starting off on the right foot by recycling that junk, and keeping a new battery properly charged.

Just to be clear: I was following the process as specified elsewhere on this board:
https://www.candlepowerforums.com/v...and-electrolyte-ratio-66-degree-acid-question

They found it not to be a waste of time, it seems. Even "very short term" would be better than nothing - this battery is less than a year old. Not dropping that kind of cash again on another one so soon seems worth a little effort. Seems like even the folks with the worst experiences with this had it work "only a year." That would double the lifespan of the battery I have here.

(Oh, and for the record -- aspirin is acetylsalicylic acid. Reduces to acetic acid under electrolysis, IIRC. That's a just fine electrolyte for a heavy-metal battery reaction. But it would likely eat the hell out of the cathode, which I imagine is why it's not used in general. But as a "short-term solution," there's no obvious reason why it shouldn't work for a little while. And the cells are still recyclable afterward...)

Hello Slinkygn,

I was looking for that thread and am glad you found it.

I should add that my efforts involved recovering larger batteries that were relatively new and were in boats that sunk. This may have played a part in the success I experienced.

Tom

Thank you Silverfox for bringing that up.

There's a big difference between the sunken batteries that were relatively new, and the ops batteries that were totally neglected, and may have had major prior normal use beforehand. A LOT of damage can happen in a year without charge, especially on flooded batts.

Here, the use of epsom salt on new-ish batteries would be to get yourself off Gilligan's island to the mainland, where the cells would be immediately replenished with normal electrolyte.

Just like with lithium, there are far too many one-off projects that are predicated by starting out as a trash-picker.

To be complete though, if one *is* going to play with trash, the simplest thing to do is perform the industry-standard 20-hour discharge rate test first and see where you stand.

For example, with say a revived 75ah battery, how many hours will it last at a .05C discharge rate? That is, .05 * 75.

A quick dummy load for this test would be to find say a standard 37.5 watt incandescent bulb, attached to a dc<>ac inverter. Since the inverter is not totally efficient, we can napkin-calc that by dividing 37.5 by 10(inverter inneficiency) (not 12v!). So near .05C of 3.75a dc being drawn from the bulb and inverter combo.

Will that load on revived trash last even 10 hours when it should go 20 hours before triggering the dead-man voltage of anywhere between 10.7 and 11.7 volts?

This way one can get an idea of where they stand if they want to play around with the trash in the garage.

I said the battery in question was a year old. I didn't say it went unused for a year. There's an awful lot here that being based on either misreading or outright conjecture. I did a discharge test. And as stated very explicitly in the original post, I *did* replace the MgSO4 with standard electrolyte afterward. (In fact, after I did what I stated in the original post and gave the first cell of two in question two distilled water rinsings and then readded the original electrolyte - one year old, as in as old as the battery, as in there is a sticker on the battery with the production date and it's a year old, and the electrolyte was fairly clean to boot - and ran into my problem, I dumped it again and replaced with brand new pre-mixed 1.265 SG electrolyte just to see if it would help.)

The thing is - NONE of that goes to answer the question asked in the post, nor is it even relevant. The identification of an MgSO4 solution vs an H2SO4 solution has nothing to do with the age of a battery. One can simply pretend the two solutions are in two different vials and answer the question. The secondary question of the acid formation from an electrolytic cell that "shouldn't" have any, too, is a chemistry question and not a "what is the state of this battery" question.

I don't need the answer to my first question now as anything more than a curiosity - I figured, well, if I don't know out of two cells which has the H2SO4 solution and which has had the MgSO4 solution for two or three days now, I better just okay it safe, dump both and fill both with the new electrolyte. But if anyone would like to answer the primary question for future reference, or the second question because it *still* stumps me, it'd be appreciated.

(Edit: and if this seems a bit snippy, that's probably directed at the insinuations - sorry, insinuations aren't overt, so more like explicit reductionary presumptions followed by long rants of cracks about how I'm e.g. "playing with trash in my garage" - from a single poster. To others, thank you for your time and effort.)

slinkygn said:

I have a flooded lead-acid battery I've been working on for a bit that was left idle *way* too long.

Click to expand...

Confusing to me. Others, maybe.

Bill

"way too long" = about two months, maybe a bit more. Definitely longer than any lead-acid cell likes to sit around... anything longer than a week without some sort of use is bad enough, really; I find that by a month or so you definitely start seeing perceptible changes in runtime and by two or three the battery needs at least some of the more atypical "interventions" if one is to recover full capacity before it's permanently not an option. (Add maybe a couple months' leeway if it's antimony-based, but not a whole lot extra.)

Thank you for asking. I understand how that could be confusing. I don't mind questions at all! And no rude comments presuming my incompetence is a nice bonus.

On another positive note, I'd also like to give a shout out to Silverfox for his post in the thread I linked above -- it was incredibly useful. I'd been digging through a lot of Internet "resources" on battery reconditioning, and his was the very first I saw that laid out a procedure that made good sense and I could get behind, rather than the 99.9% of "experts" on YouTube that left me thinking, "do they know they're basically destroying their battery?" And the idea in the linked post about doing a distilled-water *charge* after the MgSO4, not just a rinse, was one of those things that made me smack myself in the head - *brilliant*. Potentially helps controlling the Mg/Ca exchange in a modern battery that the regular Epsom salt method would create due to Mg's higher electronegativity, making the fix that much more stable. Great post, two thumbs up! A big thanks to Silverfox.

Slinkygen - no offense intended.

You seem like you are seriously interested in how the chemical reactions of Pb batts work.

The red-flag was raised because in the past - and even to this day with other chemistries - posts about reviving batteries with epsom salt or other magic elixers from those with low post-counts, used to eventually end up pointing to those trying to either sell stuff, or promote a cottage industry of hoarding dead lead batteries, reviving them, and selling them to neighbors.

It has in fact been so bad in certain areas, that they deprived government sponsored recycling centers from doing the right thing, and left neighborhoods with hazmat toxic environments in people's backyards.

You seem to be one of the very few who wants to know.

With your batt only sitting around for 2 months - which is usually far less than they would be sitting around on a retail shelf, I'd have been tempted to just refill with distilled water, and put them under a good charge, rather than do the electrolyte dump.

In the end, just do the standard 20-hour discharge at .05C and see where you stand. A suitably large dummy load can be made by using a small dc<>ac inverter, and a bulb or two in a lamp fixture. Ie, for a battery rated at 75ah, use a 37.5 watt load.

75ah * .05 = 37.5 watt load needed. (super convenient because of the inverter inefficiency 37.5w / 10v = 3.75A constant pull. Well, close enough. Will it last 20 hours until the inverter alarm goes off, or will it last only 6 hours?

Incandescent bulbs, or whatever other load you can find and go by it's TRUE wattage rating (ie, led bulbs "equivalent" wattage don't count - you need to find the REAL wattage they pull) - so standard incandescents are easier to use singly or in multiples hanging off the inverter.

Of course if one has a real calibrated load setup, that would be ideal, but this is a "quickie" off-the-shelf type of thing one can employ with a quick trip to the auto parts (and maybe home improvement) store.

Re Silverfox: Oh yes, awesome, as well as some of the other heavy-hitters here. But it takes ALL of us, you and me included to make it a community. So welcome aboard!

Heh, here I'll try to say it in the concise manner that Silverfox would, instead of my usual multi-page prose..

Epsom salt added to the electrolyte is a way to remove sulfation quickly, and make old batteries seem like new. Disregarding the physical damage to the internal lead structure caused by the expansion of hard sulfates, the epsom salt ALSO attacks the working surfaces as well as the hard sulfate.

Thus, the fix is only temporary, and even if the internal lead structure (grids, plates etc) is perfect, the harsh effects of the salt reduce your cycle-life to perhaps only 10% of what it had when new.

Because this seems to work *too well*, most consumers who have no way of judging what has happened to the battery, can be mislead (pun intended) into thinking that hoarding dead batteries and reviving them with epsom salt might be a viable cottage industry - albeit not aware of local hazmat regulations regarding weight, storage, or other factors that might come down to weigh on them.

Testing revived batteries: In many cases, revived batteries are never truly tested, or only support insignificant loads. Even if the standard 20-hour discharge capacity test is performed, and passes, in many cases the battery will not support what it was actually designed to do - as in the case of a vehicular starter battery, where damaged grids and shorted plates really expose themselves. Or if they do, the damage from epsom salt on the cycle life has already reduced operational status severely.

In my area motorcycle riding is a summer pastime. At the end of summer the bike is wedged into a corner of the garage and forgotten about until summer comes around.

I have had good luck putting a little epsom salt into the cells of a really dead battery, charging it overnight, and then using it for the rest of the summer. This is usually with manual start motorcycles. This only seems to work for one summer. The next year the battery is dead beyond any hope of revival and needs to be replaced.

The expectation before trying this is that the battery needs to be replaced. However... what fun is there in simply replacing a dead battery when we can play around in an effort to raise this battery from the dead.

Many times this worked but when it didn't I simply replaced the battery and went riding.

Tom

Exactly! Sometimes we can forget when it is just more practical to start over afresh.

I thought for sure you'd be Mr. LifePo4 by now, where _cy_ has been hanging out and teaching (awesome!) since 2012 or so on advrider:

https://advrider.com/f/threads/moto...el-wet-lithium-iron-phosphate-lifepo4.757934/

Maybe change-up your existing procedure just a little? Instead of just parking it in the corner of the garage, how about trying attaching one of my favorite charger brands, especially for bikes:

Tecmate / Optimate 3

Or one of their other versions that has can-bus connectivity etc.

When you peel back the fluff of most charger manufacturers, there is the "end-game" of float maintenance (fought about on forums from real users, shills and competitors that made for tough slogging for those that can be swayed - or never actually take the time to put a chart-recorder on the whole process for proof) that many do not get truly right. These guys do. In the lab or in the garage.

So maybe for fun, grab the cheapest *NEW* batt you can find, attach after each ride (especially if just a short conveniene-store run or for long-term off season) and see how well or how far this maintanance charger can take it!

I know I'm a year late to the party, but in reply to your first question, for future reference, you might be able to determine which cell was which by testing the specific gravity of the solution using a hydrometer (basically a turkey-baster with a weighted, graduated float inside). Pure sulfuric acid has a SG of about 1.85; battery acid is about 36% acid so has an SG of 1.265 or so at full charge. Fully saturated epsom salt solution would have an SG of about 1.33 (some conflicting sources) which would further increase when the cell was charged and lead sulphate on the plates started converting to sulphuric acid in solution, which lowers the pH (as you observed) and raises the specific gravity. However if you made a weak epsom salt solution your SG might be very close to the acid and thus make it indistinguishable.

To make this more reliable, you'd want to test the SG of the leftover battery acid and any extra epsom salt solution (hopefully you kept the excess).

It's tough, because you're essentially trying to discern the difference between a solution of sulfuric acid with or without magnesium sulfate.

actually an easier way than that would be to simply add some bicarb to each, the one that formed the white slugey precipitate is the MgSO4