FLA Battery Charge Voltage Question

MrM1

Question About Leftover Removed Acid

I have put 2 boxes of baking soda mixed with water into 3 pints of acid I have pulled out. I will still add more as the foaming has not stopped yet, But as of now the 3 pints plus water is down to 1.100 SG.

At what SG is the Acid considered to be neutralized? I am finding reference to the SG of water to be about 1.000

What should I do with the now neutralized acid? Is it safe to say pour into the ground?

Estragon

Water does have sg of roughly 1.0 (may vary a bit with impurities). Baking soda adulterates the water though, so SG may not be a good indication of neutralized.

A PH test (litmus paper - cheap and readily available) would be better. Neutral is ~7. Baking soda ~10 (base) battery acid ~0.

As far as "safe" to pour on the ground, I figure if I can eat/drink it, it's (usually, stuff like antibiotics excepted) safe to pour out. I wouldn't drink the electrolyte brew, so I'd say no. Others may feel differently though.

BB.

The sg will be affected (higher than 1.000) because of the baking soda being dissolved / in solution.

I would not put the neutralized acid on your ground where kids play or garden. I would worry about the dissolved lead content.

I would not be worried about any acid remaining in the electrolyte.

I would not put in your septic system either because of lead, although older plumbing had lead from solder and brass fixtures, as well as the old lead water pipe.

Sulfuric acid is used as drain cleaner all the time in home drains by plumbers-- stronger than normal lye based drain cleaners.

Bill

mike95490

> Sulfuric acid is used as drain cleaner all the time in home drains by plumbers-- stronger than normal lye based drain cleaners.

Whoa ! never though of that, gee the lye didn't work, so I'll get the strong stuff. ( pipes back up with foaming Acid/Lye mix )

BB.

Believe me, just the sulfuric acid drain cleaner boiled and steamed.

https://www.lowes.com/pd/CLEAN-SHOT-32-oz-Sulfuric-Acid-Drain-Opener/3371170

-Bill

MrM1

@mcgivor In your link to the Water Treatment Thread your last comment on the process at post #23 you say ...

Day 3, SG 1020@25 Deg C, start

EQ for 3 hours, temp 36 deg C, SG 1024 not temperature compensated

Put back into bank for regular service

Will see how things progress and wether cycling changes things.

Here there is mention of Acid being reintroduced (at Post #24) but no mention of the charging process and reintroducing acid to bring the cell back up to spec. Did you do it in steps as described in the PDF? And Mainly, did you re-charge at each adding step and was this at EQ voltage or at a lower gassing voltage?

I am nearing the re-add phase. Hope to start adding acid back in by this afternoon. I was unable to source 1.300 acid, the best I can find is 1.280, but that is higher than the spec 1.277 for Trojan L16s. It just may take more to bring the cell up to spec. And I will bring it up to spec very slowly over several weeks, not hours.

Tecnodave

I've seen sulphuric acid drain cleaner at Home Cheepo and ACE hardware, it is commonly used for that purpose. Sewage treatment plants constantly test ph of incoming effluent and adjust for that.

mcgivor

https://forum.solar-electric.com/discussion/comment/397123#Comment_397123

When adding new electrolyte, remember the electrolyte in the cell will be of a low value, the new electrolyte should be ~1.300, if added to the cell it will dilute to a somewhat lower value. What's really needed is a more concentrated solution, to achieve this I put a bowl of electrolyte in the sun to evaporate some of the water off.

This will take time, there will be some stratification so equalization charge is nessersary after each addition , low current high voltage, when the SG nears but is slightly below the target value, this is the time to put it back in service. Whatever you do do not rush the process, after a few cycles the SG will stabilize, if too high, withdraw and replace with water. Should the SG be too low, withdraw and add electrolyte, just be very conservative either way, check the SG after every cycle until satisfied, fine tuning if you like.

My apologies for any inconsistencies in the previous post, it was the first time doing this somewhat unconventional process, it did work to extend the service life at least until the remaining cells began loosing capacity, whereupon they were replaced.

Best of luck with your endeavors, your results may differ, but it is after all a last resort, hate to be repetitious but be patient.

MrM1

Water treatment acid removal is now done. I remove about a pint of acid 5 x's to achieve 1.100 or lower (except the first time) each time. The last time Gravity stopped rising at 1.140. Checked for 2 hrs at EQ voltage. PDF says it's done if SG stops below 1.150. Now to begin slowly adding back.

Question : does low SG result in lower battery voltage?

BB.

SG vs Battery resting voltage (and initial SG fills for different types of FLA batteries). Just an estimate of SG vs Voltage;

https://forum.solar-electric.com/discussion/comment/92455#Comment_92455

Specific gravity = single-cell open-circuit voltage - 0.845 (example: 2.13v – 0.845 = 1.285)

Or

Single-cell open circuit voltage = specific gravity + 0.845

-Bill

MrM1

@BB. Just to be clear (for my sake not yours - I know you understand), I am not trying to get an SOC from Voltage. Are you saying in the above that there is a relationship between where the SG is and the voltage? In other words, if I have a 6v battery at a particular SG and it is reading 6.40v resting, AND if I then lowered the SG in 1 or all of the cells from 1.277 to 1.160 (as I have done in the water treatment), Would the voltage of that same battery be lower? Say 6.36v? (my voltage numbers are for example only)

BB.

To clarify...

• 1.277sg + 0.845 = 2.122 volts per cell

If all cells were at 1.277 SG, then the 3 cell / 6 volt battery would be at:

• 3 * 2.122sg volts per cell = 6.366 volts

-Bill

mcgivor

The cell with the lowered SG will have a lower voltage, in a normal healthy cell during discharge the soft crystals from the electrolyte are deposited on the plates making the solution less dense, hense lower SG. During the charging cycle the crystals are disolve back into solution, in turn raising the SG.

What you have done with the water treatment is break down the hardened crystals that cause sulfation, rather than going into solution, they are removed then replaced with water, because the crystals disolve more readily in a weaker solution. This is continued until there is no further breakdown and the SG remains constant, so the cell is in actual fact in a low state of charge due to the low SG, therefore at a lower voltage.

Once the addition of a more concentrated solution is administered to reestablish the desired SG, the voltage will increase, because the required chemicals will be available to the plates, the whole chemical reaction is more complicated and described in more detail here, https://www.itacanet.org/a-guide-to-lead-acid-battries/part-1-how-lead-acid-batteries-work/

MrM1

Thanks so much great help guys

MrM1

Ok next question: How long does it take the battery to cool down if the charge temp was up to 40*C and outside temp is between 65-85*F? Last night stopped charging before i hit 40*C and battery sat overnite. Cooled to around 29.6*C. Today Battery sat all day. Did some EQ before I left this morning and it was 33*C. Gone all day- 10 hours. No charging / discharging. Come home and it was still 25.8*C. Today outside was 85*F

mcgivor

They take a while because the heat is held in the lead and the case has a poor heat transfer coefficient, some airflow will help if the ambient is significantly cooler.

That's my dilemma with my LA bank right now, the battery temperature is 48°C, the daily ambient high is 42°C, only by midnight dose it cool below 35°C, been this way for over a week now, everything is hot, even with a fan blowing over them they drop to 40°C by morning then the same thing the next day, with just normal charging, thankfully the beer is cold. Hope the forecast is wrong, the prediction is there are at least 2 more weeks of this, everything suffers, batteries, electronics and to compound everything the panels have low output.

MrM1

Also having a hard time "home brewing" my acid to above 1.280. Letting it set in the sun in a glass bowl ... and then there are 3 bugs in it, so I have gone to placing a screen over the bowl. And it has been in the bowl since 8am (4.5 hours) and has only risen just a little. :/

The re-add is going really slow otherwise. And EQ is not rising each new add but by only 3-8 points higher than when each add is first put in. So not much going on with that. Becoming critical I make or find some 1.300 acid.

t00ls

have a look at my reply to this thread...I havent read all the replies here, but this may help

https://forum.solar-electric.com/discussion/comment/397371#Comment_397371

MrM1

Water Treatment Update

So far so good. After finally getting the SG to stop rising above 1.150 I started adding replacement acid 1 pint at a time, the same amount as was taken out each time. Then EQ and remove old / add more new. It has taken a while, but I have managed to get the suspect cell back up to 1.250. Process is slow going now. I'm having to make 1.300 acid from 1.265 acid by letting it sit in a bowl in the sun = water evaporation. It is taking 2 sunny days for each pint... And the last pint only raised the SG from 1.240 to 1.248. I've got another quart that should be ready tomorrow afternoon.

Question. If the SG is not rising when EQ voltage is applied , then is the battery fully charged at the SG level? I had to let it set over the weekend at 1.250 (other 2 cells where at 1.280 and 1.290). Is this causing sulfating?

Results so far:

• Suspect battery before was lagging 0.55v lower than other 3 batteries in float
• Lagging 0.85v lower when charging
• After water treatment so far that gap has closed to 0.2 in float and 0.28 in charge.
• BUT doing a short EQ today at 80°F (suspect battery was at 21.5°C) battery temp in the suspect battery rose to 26.5°C in 2 hours at 32.4vEQ. Kinda fast as other batteries were at 24°C

Other wise I'm cautiously optimistic. I have not put the bank back into service yet. No loads. Just add acid EQ for an hour, check SG float, Add more acid, repeat till sun goes down.

mcgivor

The low cell hopefully has the sulfation removed, therefore technically it would be at a slightly lower capacity than the other cells, this shouldn't cause sulfation. Keep adding 1.300 until very close to the target, then run a few deep cycles with a short EQ, then take a SG measurement it may rise slightly, remembering the electrolyte level must be the same as the other cells to get an accurate comparison. Dot try to rush the process, my observations were that the SG increased slightly after a few cycles, which is the rationale behind saying get it close, perhaps ~ 1.275.

Estragon

May not be significant, but something to be aware of...

SG readings are temperature dependant. For a few °C it's within measurement error, so not an issue. If though, for example, you read SG of the bowl in the morning at ~20°C, and after sitting in the sun all day it was more like 40°C, the acid will be less dense and the SG difference (~.01) may be more material to the task at hand.

FWIW - just something to keep in mind if temps vary a lot between readings.

MrM1

Thanks @Estragon and @mcgivor

Water treatment is getting closer and closer to completion. After 2 days of evaporation, next batch of acid made it to 1.300 this afternoon. Was able to get about a pint and 3/4's. Got that mixed in and acid level is now at 1.260 in the suspect cell. Did a 45 min mixing charge at 30.4v. Will make up another couple pints and that should have me near 1.270 give or take. And then I will put the bank back into service.

MrM1

Water Treatment Update. 

Without going into all the details, (read mcgivor's thread for more info) following the water treatment procedure,  over about a month,  I "walked" the suspect cell down to below 1.100 SG several times refilling with distilled water to dilute the acid content,  EQ charged until SG stopped rising,  and repeated until the SG would not rise.  Then re-introduced new 1300 acid slowly over time until the battery cell was back up to spec at 1.277 by gradually removing acid and EQ charging slowly.  It took a long time,  mostly because the only acid I could source was 1.265 and so I would put a quart out in the sun in a bowl,  and evaporate off the water until it reached 1.300.  It got a few bugs and dust in it so I would filter it each time with a coffee filter before using it.  But this process Sometimes this took 2-3 days and had to be done 4 or more different times. 

All of this was done as a last ditch effort,  I figured the battery was "toast" so I had nothing to loose (but time) and knowledge to gain.  I enjoyed the learning. 

Results.  The battery still seems to be acting a little poorly.  4 things are troubling.

1. I have done 1 deeper discharge of the bank since water treatment completion (yes I need to do more).  But I find it difficult to get the weak battery back up to fully charged - 1 cell goes to about 1.260, 1 to 1.250, and the suspect cell goes to 1.240,  but all other cells in the bank reach 100% SG 1.280 +
2. Reason for #1 seems to be that when charging, there is about 0.9v difference in charge voltage between the suspect battery and the other 3 batteries.  If charging at 29.6v,  3 batteries will be at about 7.65v while the lagging battery is at 6.7v - or not even at a gassing voltage. BUT 1 cells is gassing pretty well,  the suspect cell is not hardly at all.  To get the entire battery up to a gassing voltage,   i have to charge the bank at 31.2v or more.  This puts the other 3 batteries at a constant state of EQ charge each time at 8.1v +/-.  I did purchase a battery balancer and this helped to bring the voltage difference to about 0.5 when charging.
   
3. Temps.  Ambient temp here is 93F high and 72F low.  3 batteries go to 28C while charging,  Suspect battery reaches 33C.  And at night the suspect battery falls to 27C while the others go back to 25C.  More troubling is that even when disconnected from the bank,  the suspect battery's temp seems to go down very slowly.  I had it just sitting for 24 hours and the temp probe on the side did not get lower than 26C
   
4. The suspect Cell does not seem to be using any water,  Even when EQing this battery by itself.  The other 2 cells are using a little but the suspect cell stays full.  The suspect cell does gas,  but not as much as the others. 
   

Doing a lot of research,  I found a section at Battery University in a post about Corrosion, Shedding and Internal Shorts that possibly describes what I am seeing.  

Electrical short is another failure mode, especially with starter batteries in trucks. As the battery sheds its lead to the bottom of the container, a conductive layer forms that gradually fills the allotted space in the sediment trap. In time, the now conductive liquid may reach the plates, creating a shorting effect. The term “short” is a misnomer and elevated self-discharge or soft short would be better terms to describe this condition.

Soft shorts are difficult to detect because the battery functions normally immediately after charge and everything seems fine. In essence, a charge wipes out all evidence of a soft short condition, except perhaps an elevated temperature during charge that may be noticed when touching the battery housing. However, once rested for 6–12 hours, the battery begins to show anomalies such as a lower open circuit voltage and reduced specific gravity.

So if this is why I am seeing such a voltage difference when charging (resulting in this one battery not getting charged) and these Elevated temps when charging,  Am I about to experience a really bad day of Thermal Runaway? 

What I have found is I can  just use the bank for float service and occasional discharge,  and then struggle and EQ to get it back to fully charged.  What this allows me to do is use solar thru the day to power loads, while floating the batteries,  but grid at night not discharging the batteries but 1-2%.   This would work for me for a long time as I only need to discharge the batteries if the grid goes down ... BUT I don't want to do this using the batteries in float service IF this is a dangerous situation.  

Dave Angelini

You probably will get a hurricane and then you will know what to do. Seriously other than good fun, time to buy a decent battery.

Estragon

I don't know what the odds are of catastophic failure, but I wouldn't chance it. It may just get progressively worse, but likely won't get any better. Like Dave implies, Murphy's law says the battery will let you down when it you need it most!

jonr

I agree - replace it. Your balancer with help with the difference between the new battery and the others in your string.

MrM1

So it would be acceptable to replace just the one battery?   The bank is 18 months old.    I know it is not ideal,  but would it at least let me get 1-3 more years out of the entire bank?  

I plan to write Trojan now that I have done all I can do and see if they will offer any "help" in the form of warranty etc. 

But If I replace the one battery,  and if I go back with same brand / model type ... would it make any sense to get one with slightly less capacity because the other are older and probably would have less capacity than a new one of the same  capacity.  In other words,  These that I have are 435Ah,  but Trojan also makes a 370Ah and a 420Ah in the same line.  Would it make any difference to replace this one 435 with a 420 to combine it with the older 3 435s?

Estragon

AFAIK, generally speaking a new battery will soon resemble the apparent age (as opposed to actual age) of the existing bank.  If the other batteries are in good shape, I'd be tempted to replace just the failed one.

As for replacing with one with different capacity, I'd check to be certain the new has exactly the same charging regime as the old.  If the same, 420 is close enough to 435 IMHO.  My identical L16s likely vary by more than that.

BB.

Assuming all the other cells/wiring/charging systems are OK, just replace the bad battery with a new one. And continue monitoring.

If your goal is 1-3 years of extending battery bank life, I think that is a very reasonable goal and you should achieve it easily.

The question is, after 1-3 years, if you have another battery begin to fail, would you replace that one too, or the whole bank for another 1+ year of life?

No right or wrong answer here, and predicting what will happen next... Who knows. Just monitor and address new issues (if any) as they arise.

-Bill

mcgivor

@MrM1

Before giving up, allow for a few weeks of minimal loads, or better yet no loads, lead acid batteries sometimes need a good long charge, something solar itself cannot offer. Being that it was a nothing to loose venture to begin with, nothing ventured nothing gained, or lost in this case. As far as temperature is concerned, along with catastrophic failure the risk is extremely low, the wells in tall cells are pretty generous being designed for the purpose of preventing sludge front creating a short circuit. Agitation may help to dislodge any remaining material from the water treatment, don't be gentle lift and drop the battery several times, from a couple of inches.

Yes the best solution may be to replace the battery in question, but it seems to me at least you have achieved significant progress from where you were in the beginning, why give up now. Obviously results will vary, the importance of the bank must be taken into consideration, even a slightly weaker battery may still provide enough energy in the big picture, if it were me I would give it some more time, just an opinion.

.