Refurbish process for forklift batteries

[Consumerbot3418]

I bought a DC Solar trailer from a bankruptcy auction, and it has a pair of 48V GNB Tubular LMX batteries on board, wired in parallel. When I took possession, I took readings of individual cell voltages (all were fairly close), and topped off the water. Then it just sat unused, with the Midnite using onboard PV to keep the batteries in float for about 6 months, with some intermittent use charging an EV. During that time, I also ran equalization using the on-board PV.

I finally got around to using the trailer (and batteries) to power our house, and it looks like there's a lot of missing capacity. I took SG readings, and found that within each battery, most cells were pretty close, with just a few that were lower than the others by .005+. However, between the two batteries, the SG readings of one battery are significantly higher (over .01) than the other. I've also noticed that all cells in the battery with higher SG readings has already lost water down to the plates.

I'd expected these batteries to be in similar condition, since they spent their lives installed in parallel, but it seems they're quite imbalanced.

I'd like to locate and resolve the source of the imbalance (assuming it's external), and systematically refurbish the batteries as best I can. I have a DC clamp meter and a bench power supply that can do 5 amps at 60V.

Any ideas about figuring out the cause of the imbalance? I know I could apply a load or charge current and see the difference, but how could I isolate the cause? Power from the batteries to/from the inverters via welding cable to a pair of 350A Anderson connectors that combine to a single. I noticed the Midnite charge controller is wired directly to the positive battery terminal of the battery that has lower SG readings. Maybe I should start with eliminating that wire?

I'd also welcome any advice about refurbishing old forklift batteries. After a series of equalizations has been performed, and no more raise of SG readings, would it be appropriate to add battery acid to cells that indicate lower than the others?

 

[OzSolar]

I'd also welcome any advice about refurbishing old forklift batteries. After a series of equalizations has been performed, and no more raise of SG readings, would it be appropriate to add battery acid to cells that indicate lower than the others?

It it was me I'd equalize them with the Sunny Islands before I went down any other roads.

I've fiddled around with a few of those trailers. Those solar arrays are pitifully undersized to equalize those batteries and for that matter to even adequately charge those big forklift batteries to begin with. What is the SG of the packs?

Can you get AC power to them? I had to hook them up to my shop and use the Sunny Islands to run an equalization charge, several in fact. That's a preprogrammed cycle in the Sunny Islands that takes 8 hours @ ~2.6 volt per cell if memory serves me correctly. They started to act a lot better after that.

 

[Consumerbot3418]

It it was me I'd equalize them with the Sunny Islands before I went down any other roads.

I've fiddled around with a few of those trailers. Those solar arrays are pitifully undersized to equalize those batteries and for that matter to even adequately charge those big forklift batteries to begin with.

Yeah, the trailer is ridiculously under-paneled, but a series of sunny days in a row (and no use) would allow me to get the batteries up to a decent EQ voltage and keep it there for hours at a time. Now I've got a larger 8kW AC-coupled array that can easily produce enough power on sunny days for an equalization, assuming I start the day with a full battery.

What is the SG of the packs?

Yesterday, battery 1 had, on a representative/pilot cell, about 1.270, whereas battery 2 was at 1.275. All the cells in battery 2 were low on acid, so I added water to them (about 4 gallons!), disconnected it, and put it on a float charge of 54.5V overnight and all day today, while I ran an equalization at 62V for about 6 hours on battery 1. Now I've got 1.277 on battery 1, and 1.170 on battery 2.

I was surprised to get such a low reading on battery 2 after it had been on a float charge for about 24 hours, but then I had a thought: might the SG reading be affected by water loss (or gain)? The manual for the battery says it should be between 1.295 and 1.345 at 77ºF. And to add water when it reaches 1.345, so I assume it means the SG will increase over time, as water is lost. So maybe it went down so much after I added water? I suppose I need to spend more time reading and learning.

Can you get AC power to them?

This is a sore subject. My utility is telling me that they consider any "solar inverter" to fall under net metering, and insist I'm not allowed to connect it to grid power without submitting drawings, getting their approval, and having it inspected... even if I have no interest in net metering! This is why I mentioned my bench power supply--I don't have a 48V charger besides the Sunny Island, but the power supply can get the battery up to 60 volts and keep it there indefinitely... I've got it set to do that overnight tonight, in fact.

I had to hook them up to my shop and use the Sunny Islands to run an equalization charge, several in fact. That's a preprogrammed cycle in the Sunny Islands that takes 8 hours @ ~2.6 volt per cell if memory serves me correctly. They started to act a lot better after that.

On a FB group about these trailers, there's been some discussion about what the "correct" equalization parameters are, and they aren't necessarily the defaults in the Sunny Island. I've got the manufacturer's recommended settings (2.67/cell for 4.5 hours!), and I've also been reading the Rolls user manual. It looks like I need to track the SGs as the EQ is happening, halt the process if they plateau, then try again after cycling for a few weeks. Wish my power supply could go a few volts higher, so I didn't have to try to equalize with PV in winter!

Oh, I just came across a note in the Rolls manual confirming that SG goes up as water is lost to evaporation. Makes sense. It doesn't indicate when it's appropriate to add acid, unless spilled or indicated by their tech support.

 

[OzSolar]

Believe or not "that little voice" was telling me you probably had a decent grasp of the situation already.

Yesterday, battery 1 had, on a representative/pilot cell, about 1.270, whereas battery 2 was at 1.275. All the cells in battery 2 were low on acid, so I added water to them (about 4 gallons!), disconnected it, and put it on a float charge of 54.5V overnight and all day today, while I ran an equalization at 62V for about 6 hours on battery 1. Now I've got 1.277 on battery 1, and 1.170 on battery 2.

What!?! One of batteries went from 1.275 to 1.170 after charging? While in parallel with the 1.277 one? That's a head scratcher to me. I've maintained a few dozen off grid battery banks built out of big 2V cells going on 30 years now and have never seen that. Keep in mind I'm self taught and am certainly no authority on FLA as it's just one of many things I do (badly).

The times and voltages you mentioned should have been plenty of time to stir that freshly added water throughout the cell and not give you false SG reading. You visually confirmed that 1.170 was bubbling for hours during this charge? Of course you're using the instrument properly.
Confirmed with different hydrometers? Side note: Midnite makes a really nice one that I don't have but I keep several ~$25 refractometers from Amazon that I really like.

might the SG reading be affected by water loss (or gain)? The manual for the battery says it should be between 1.295 and 1.345 at 77ºF. And to add water when it reaches 1.345, so I assume it means the SG will increase over time, as water is lost. So maybe it went down so much after I added water? I suppose I need to spend more time reading and learning.

Sounds like I need to learn more as well. I've maintained mostly HUP's, Surrette's and Trojans and have never seen a SG recommendation of over 1.280. Can you send a link to that manual? I've two of those trailers under my care at customers and I'd love have it. I've looked and looked and have never been able to find it.

but the power supply can get the battery up to 60 volts and keep it there indefinitely... I've got it set to do that overnight tonight, in fact.

Hmnn... Combine that with the low SG I would call the battery severely sulphated. In my experience when you can keep a battery at it's return amps (~1 amp per 100 amp hour) with that high of voltage it an equalization charge is order. Several long ones in fact. I don't know how to explain what's going on when combining that with what else you've said though.

I have a theory.... So you've isolated that battery? Isn't it as simple as disconnecting the Anderson plug on other battery? My memory is that how they were wired up. Let me know what the overnight test with power supply tells. If my theory is correct you should find the battery at a LOWER voltage that when you started and the power supply still maxed out at 5 amps. I do think it's going to take more amps though. As you knock the sulphation off the plates it takes more and more amps to keep the battery at that higher voltage, eventually the SG starts to respond, the voltage climbs back up to the ~2.65 VPC and finally the amps start tapering until as the SG reaches ~1.275.

Oh, I just came across a note in the Rolls manual confirming that SG goes up as water is lost to evaporation. Makes sense. It doesn't indicate when it's appropriate to add acid, unless spilled or indicated by their tech support.

I've never seen that note and I though I had read through most of Surrette's literature. That's been a debate of mine because while it does make sense I also think that it was really an the manufacturers would supply a correction charge like they do with temperature.

 

[OzSolar]

Here's one of the better generic battery maintenance guides I've seen. It's not going to answer your specific questions but I do like how it explains how batteries work.

 

[Consumerbot3418]

What!?! One of batteries went from 1.275 to 1.170 after charging? While in parallel with the 1.277 one? That's a head scratcher to me.

No, no... I had disconnected battery 2, and just applied a float charge after adding water to all the cells. The EQ run was performed on battery 1 by itself, since I had the impression that EQ on both batteries in parallel was boiling off water from battery 2, and not accomplishing anything on battery 1.

I've maintained a few dozen off grid battery banks built out of big 2V cells going on 30 years now and have never seen that. Keep in mind I'm self taught and am certainly no authority on FLA as it's just one of many things I do (badly).

I have to laugh at this, as I'm much the same. Shallow, working knowledge of a really broad variety of subjects. Sometimes I'd like to be an expert at just one thing--a real craftsman who can take pride the fruits of his labor, instead of cobbling things together that (usually, eventually) work alright.

The times and voltages you mentioned should have been plenty of time to stir that freshly added water throughout the cell and not give you false SG reading. You visually confirmed that 1.170 was bubbling for hours during this charge? Of course you're using the instrument properly.

No, it didn't, since it was resting at a float voltage of 54V. Being aware of stratification, I did attempt to agitate the solution by sucking and squeezing the bulb vigorously multiple times before taking a reading.

Being frustrated with trying to hold the hydrometer exactly level, I had already considered buying a refractometer. Went ahead and ordered one like the one you linked to--thanks for the suggestion!

Sounds like I need to learn more as well. I've maintained mostly HUP's, Surrette's and Trojans and have never seen a SG recommendation of over 1.280. Can you send a link to that manual? I've two of those trailers under my care at customers and I'd love have it. I've looked and looked and have never been able to find it.

Sure thing! Bottom of page 2: "Following the first 90 days of service, the battery should reach its normal operating specific gravity of 1.295 to 1.345 at 77° F (25° C)."

I have a theory.... So you've isolated that battery? Isn't it as simple as disconnecting the Anderson plug on other battery? My memory is that how they were wired up. Let me know what the overnight test with power supply tells.

Yes, the Anderson plug makes it simple to isolate the batteries. I had isolated it the previous evening, before adding water and leaving it at float voltage, then finding it with the low SG reading. Last night, I reconnected it, left it at 60V@5A, and this morning, it was still dumping 300w into the paralleled batteries. Voltage didn't go down. SG on battery 2 went up significantly, though, and went up a bit on battery 1, as well.

I've never seen that note and I though I had read through most of Surrette's literature. That's been a debate of mine because while it does make sense I also think that it was really an the manufacturers would supply a correction charge like they do with temperature.

Yep, it's the first note on page 21 of this document. Don't know how they could manage a correction chart, as you'd need a way to measure the water level.

I think I'm going to take your advice, and start out with some equalization, following Rolls' advice to monitor SG, and stop EQ when it no longer climbs. I'll just use the generator, since my power supply doesn't put out enough juice, and there's no enough sun, either. Good to exercise the generator every once in a while, anyway. Of course (as per that note), if I'm boiling off water, the SG is going to keep climbing, then going back down when I water the cells, so I'm not really sure how to go about doing this in a methodical fashion. I'll give it shot, anyhow!

 

[Zwy]

You cover the plates, do not fill full before equalizing. Take readings before adding water, if it makes you feel better but it really isn't important. Write down every hour what the SG readings are, any water freshly added will be long mixed in an hour. If you have a cell getting water level very close to the plate (which really shouldn't occur) then add a little, not too much. It will mix in under EQ quickly.

 

[Consumerbot3418]

Something I should have brought up in my initial post... these batteries are mounted on a trailer. I drove it 750 miles myself (and its prior history is unknown), and when I arrived at my house, the batteries needed many gallons of water, with some cells just below the tops of some plates. I also have no idea what the maintenance history of the battery is, but it seems obvious that in the process of towing this trailer, a certain amount of acid sloshed out of the vent caps. There's also a chance that the cells were overfilled in the past, and some boiled out... The tops of the batteries definitely show evidence of prior acid spillage.

My biggest question is: how do I go about correcting the likely wrong/imbalanced acid? This is the information that's hardest to find. Everywhere I look, it says only add distilled water unless you're sure some acid spilled/leaked out, but nowhere have I found how to determine the correct amount. The closest thing I can find is this page, where step 14 of 18 is "Sulfuric acid is added to some cells in order to even out cell voltages under load."

I failed in my attempt to equalize yesterday. Even though I set Sunny Island to EQ charge at 66V, it never went past a target voltage of 63.0V for some reason. I've had a battery temperature sensor warning recently, but that warning went away, and I have an accurate battery temperature indication now. But I never could figure out why it was only targeting 63V (<40A), meanwhile the generator was wasting expensive diesel... I left my 60V/5A power supply connected overnight (circa 220 watts of charge power after losses to the inverters), and after about 7 hours of sitting at about 58.2 volts, the voltage starting going up. I'm wondering if I didn't unlock some extra capacity with the hour spent at 63V (my failed EQ attempt)?


Sunny Island is still targeting 63.0V, regardless of what I enter for EQ cell voltage parameter, but I'll have to sort it out some other time. I think for today, I'll just let it do a longer EQ at the lower target voltage (for now) using PV, with loads disconnected.

 

[OzSolar]

My biggest question is: how do I go about correcting the likely wrong/imbalanced acid? This is the information that's hardest to find. Everywhere I look, it says only add distilled water unless you're sure some acid spilled/leaked out, but nowhere have I found how to determine the correct amount. The closest thing I can find is this page, where step 14 of 18 is "Sulfuric acid is added to some cells in order to even out cell voltages under load."

Maybe you could get this guy to come over and help you?

I've moved those trailers around as well and didn't observe electrolyte sloshing out. My gut is that you don't have a battery acid problem but I have no idea how to help you prove or disprove it.

No doubt that you're seeing signs of spillage. It's very common for people to overfill a discharged battery and then have them start puking out electrolyte as they reach full charge. How many times can you do that before you have problems? No idea.. wish I did.

Could it be as simple as dumping out what's in there and replacing it with fresh bulk electrolyte from your local auto parts store? That way you're starting with something fresh of a known dilution (concentration?). That assumes all battery acid is the same but again, I have no idea. That's a back breaking prospect of pulling all of those cells out though.

I'm trying to evoke Cunningham's Law to get us both some help. (that will make sense after you're here for a while)

Not suggesting you do this but I already had a big chunk of 6/3 rubber cord laying around was able to get close enough to my breaker box. You might be able to get enough amps to the trailer with a #10 Romex on a 30 amp breaker. Just set the max input on the SI's to 24 amps.

There wasn't a generator on my trailers but there was one of those pin lock style plugs.

 

[Consumerbot3418]

Maybe you could get this guy to come over and help you?

I’d seen a similar video before. Pretty impressive! So… Based on the battery manufacturing/recycling industry, I guess the only way to completely freshen a battery is to melt down the plates and put fresh electrolyte in.

My gut is that you don't have a battery acid problem but I have no idea how to help you prove or disprove it.

I think you’re right, but I’d really like to know for sure. Even if it’s not a problem, I’d love to optimize, if it’s feasible.

Could it be as simple as dumping out what's in there and replacing it with fresh bulk electrolyte from your local auto parts store? That way you're starting with something fresh of a known dilution (concentration?). That assumes all battery acid is the same but again, I have no idea. That's a back breaking prospect of pulling all of those cells out though.

I’d probably try to siphon it, considering the cells are welded together, too. But it’d be a considerable expense, and a lot of work. Maybe a last resort, *if* it’s determined that I actually even have a real problem with acidity.

I'm trying to evoke Cunningham's Law to get us both some help. (that will make sense after you're here for a while)

I’ve been on the internet since the days of USENET, so it already makes sense. ?

… on a 30 amp breaker. Just set the max input on the SI's to 24 amps.

I’ve already got 6/3 Cu to the trailer, but my utility insists I’m not allowed to connect grid power to the sunny island AC1 without an approval for net metering, even if I don’t backfeed, and only use it to charge/pass through. I’m skeptical that they have that authority, but intend to keep my promise not to do that.

I don’t think PV or generator output is constraining me, though—It’s gotta be the sunny island temperature compensation gone awry. Hopefully I’ll figure that out soon.

 

[Zwy]

I would not worry about acid concentration. Simply fill with distilled water above the top of the plates. Charge thru bulk and absorb. Then attempt an EQ. Monitor battery temp, charge voltage. In my experience, once battery temp hits around 100F, the electrolyte and plates resistance change enough that all you are doing is converting amps to heat. Let the battery cool to room temp, do an absorb charge and set at float overnight. Discharge with a capacity test and recharge. If you are attempting EQ on abused batteries, when the voltage measured at the battery lowers while charging or if you see the voltage dropping on the charger, then either some plate material has cleared or the plates/electrolyte resistance changed due to heating. If the voltage continues dropping, stop attempting EQ, let the battery cool down (preferably overnight) and cycle with discharge test or attempt an absorb followed by float overnight with a discharge capacity test.

A few things need to happen if heavy sulfation has occurred, the plates need expansion and contraction for hard deposits to be possibly removed. Cycling the battery and ending with an EQ gets the acid stirred off the bottom of the plates. The plates also need time to convert softer lead sulfate deposits back to acid and lead.

I've been working on a set of used, abused and left for dead T105's for about 2 weeks now. I was possibly starting a thread about them but this might be as good a place as any. These had exposed top plates, and hadn't been charged in 2 years. Batteries were 4 to 5 years old. I've recovered 80% capacity on 2 pair thus far. I cycled them heavy, tried various charge voltages. For a pair, I'd usually run around 15v for absorb on extended time frames, then cycle with a capacity test. Worst pair was 115Ah at 20hr rate, I have recovered it to 155Ah last test but currently testing it as I type. I did not attempt any equalization at over 16V for any pair until the last few days. Other 2 pairs tested 150Ah and those have recovered to 180Ah thus far without any EQ attempt. I prefer trying to slowly convert sulfation back to acid and lead before attempting to knock it off the plate. My goal has been minimum 80% capacity, preferably 90% but that might be a stretch.

I've watched this video about 10 times plus his other desulfation videos and thought what the heck, I'll try this and see how far I get. Effort in futility? Could be, the idea was to recover these batteries enough that a golf car was usable around the yard (4 acres) for my wife with yard work and swap out the resistor for a Alltrex controller/solenoid/throttle pot with the eventual replacement of the 36V FLA batteries with 48V of LFP. Small steps and recovery of the batteries is environmentally friendly.

 

[fromport]

Maybe you could get this guy to come over and help you?

There is a lot of black stuff in the fluid if my batteries when I suck it up with the SG meter.
I have given up on them.
Soon I will lift them off and replace them with some stacked li-ion batteries.

 

[Zwy]

I haven't had any black stuff, just water levels and had been sitting. If black burnt material or hydrogen sulfide was present when charging, I'd junk them. I have had neither fortunately. I have used up over 2 gallons of distilled water. I keep plates covered about halfway between plates and bottom of fill hole. Measured around 2.0V per 6V T105, wasn't promising. Added water to cover the plates, put a power supply on each battery for 7.4V and let them take on electrons. I just finished the capacity test on another pair, it wasn't the worst pair that originally tested 115Ah. This pair originally tested 140Ah, then 154Ah, then 174Ah, then 181Ah and last test which had EQ after recharge got me 184Ah.

I'll keep playing with them. Worst pair is now on capacity test and as I discharge at 20 hour rate of 11.25A it will be sometime tomorrow with results. This is a slow process, not for those that don't have patience.

 

[Zwy]

The 115Ah pair went from 115Ah to 154Ah, to 155Ah, to 158Ah on last test. These actually are the best equalized pair on SG. I might split them up down the road and pair with a different battery similar in SG. I have split the pair and charged individually, that was the 154Ah to 155Ah test.

I'll try different levels of charging, the best results actually were voltages just above bulk with extended time frames. The You-tuber I linked mentioned in one of his videos that he had run tests with high charge voltages and high amps compared to lower charge voltages with lower amps with extended time frames and found there wasn't any real difference on recovery. It was more about exercising and cycling the battery.

 

[shadowmaker]

I'm a complete newbie with solar power and batteries, so I need your help. My vertically mounted bifacial setup will be 44kw, but I still have a lot to be build before it operates. I have ordered 4 x 5kW lifepo batteries, but got also almost 20 year old forklift battery for free (also got 7,2kW and 3kW UPSs which are fine). I have 4 inverters: 2 x 15kW on grid and 2 x 15/12kW hybrid. Actually those hybrid ones haven't arrived yet.

The problem is with that 911kg lead acid battery, which have been unused for half a year or so. It's an 48V Exide battery from 2005 and has 24 5EPzS 625 cells (30kW/5 hours). Tested those cells and those were around 1.96 - 1.99V. Previous owner changed one cell to the pack about a year ago and that new one was well above others at 2.04V.

I have 24V/60A charger, so I topped cells with distilled water and started charging half of those cells =24V. At first it charged around 55A and boiling was easily audible, then after an hour or two it went down to 35A. Next day there was a red error light blinking and charging had stopped. I put charger on again and at first it charged 55A, then after an hour or so dropped to 35A again. Maybe after six hours or so red alert was on and I just put it on again. Then after 4 hours or so I noticed that some acid was leaking on top of those cells and stopped charger. Cells were around 37C or 100F and boiled violently. Now that they have been sitting for two-three days cells read 2.06V consistently. I tried to charge the other side too and it went exactly like the other side, but started to leak acid much sooner. That side is now at 2.00V, but that new cell is at 2.14V.

Although my charger is 30 years old, it has additional charging and maintenance charging on it. Problem is that it jumps straight from charging to error every time. Also problem is that I topped water before charging, so now It leaks acid if I try to charge it. My fault, I know it now.

Any suggestions how to proceed? Should I take some acid off from the cells and add it back later when there's more room for it? I have gravity meter (got it today), but haven't got time to measure cells yet. I also have many smaller 24V and 12V chargers lying around. Have also 12V 3kW inverter for capacity test, but I think I need to refurbish the battery first as it has been sitting unused for so long. What I have found out myself is that there are so many different opinions how to do this.

From everything I have read, the most logical way to do this is is to overcharge (over voltage with high current) and then let to float for days. This way sulfation can be detached from the lead and dissolved back to acid. My charger seems to make 28,8V and max 55A, so if I solve the acid leak problem, then maybe charging 8 cells (=16V) with 28.8V for 2-3 hours and checking that temperatures won't go over 45C/110F and repeat that three times to get every cell treated in the battery (actually not sure if I want to do this to that one new cell). Not sure if my charger, as old it is, will tolerate overcharging. It may be too "clever" to do this. If overcharge is a success, then charging again normally (12 cells/24V) and hope my charger will enter additional charging and eventually maintenance charging. Then it's time for capacity test.

Ideas, anyone?

 

[Zwy]

I would find a way to limit charge current. What is occurring is the charger is inputting high amps, thus the boil. The higher voltages can come later. A few ways to do this is a power supply with adjustable output, constant current and constant voltage. Another is to take a regular charger and have resistance in series with ground or positive lead. An old car headlamp will work but you would be limited to a 12V charger. Personally, I'd use the power supply as you get the added benefit of seeing voltage reading drop as battery resistance decreases plus you can do 24V and adjust current to a low level.

An example is the original desulfation video put out here using an old buzzbox with a resistor, later versions he moved to an adjustable power supply.

After it has been charging for some time slowly, and this could take several weeks, enough water will have boiled off and much of the sulfation will be gone from those cells. You will have to monitor water level daily if not twice a day. The worst thing that will kill a cell is to run it dry. Patience is key, I capacity tested the 115Ah pair yesterday after letting it sit for a few days at absorb charging voltage with current at just a few amps and it went 167Ah from the 158Ah of the last test. That is a 45% improvement in capacity, but still not to my goal of 80% or above. One pair is getting close to 85%, it's all a matter of time, slowly charging and discharging to get capacity back. This is why solar can work well for desulfation, low charging rate and low discharge. I've been working these 6 batteries over 2 weeks, it will take time.

 

[shadowmaker]

I would find a way to limit charge current. What is occurring is the charger is inputting high amps, thus the boil. The higher voltages can come later. A few ways to do this is a power supply with adjustable output, constant current and constant voltage. Another is to take a regular charger and have resistance in series with ground or positive lead. An old car headlamp will work but you would be limited to a 12V charger. Personally, I'd use the power supply as you get the added benefit of seeing voltage reading drop as battery resistance decreases plus you can do 24V and adjust current to a low level.

An example is the original desulfation video put out here using an old buzzbox with a resistor, later versions he moved to an adjustable power supply.

After it has been charging for some time slowly, and this could take several weeks, enough water will have boiled off and much of the sulfation will be gone from those cells. You will have to monitor water level daily if not twice a day. The worst thing that will kill a cell is to run it dry. Patience is key, I capacity tested the 115Ah pair yesterday after letting it sit for a few days at absorb charging voltage with current at just a few amps and it went 167Ah from the 158Ah of the last test. That is a 45% improvement in capacity, but still not to my goal of 80% or above. One pair is getting close to 85%, it's all a matter of time, slowly charging and discharging to get capacity back. This is why solar can work well for desulfation, low charging rate and low discharge. I've been working these 6 batteries over 2 weeks, it will take time.

I pulled watering hoses off with floats on them, so there's now room for the acid/water. I changed chargers and use now 24V smart charger that is capable for 31V/12,5A. It has been charging for full day now at 28V/11A. It did accept even 28,8V/55A charge easily, so maybe 11A current is low enough without any resistor for such a big battery?

 

[Zwy]

I pulled watering hoses off with floats on them, so there's now room for the acid/water. I changed chargers and use now 24V smart charger that is capable for 31V/12,5A. It has been charging for full day now at 28V/11A. It did accept even 28,8V/55A charge easily, so maybe 11A current is low enough without any resistor for such a big battery?

The problem with high amps is it will boil the water, the problem you were trying to get away from. Leave the 12.5A charger on for a few days, it will reach absorb after bulk and the current will decrease while voltage will move closer to the 31V. The 31V will actually work well for desulphation, it takes longer than charging at EQ levels above 32V which would be above 2.65V per cell for EQ, but is still effective, keeps battery temp low and water consumption down. I wouldn't get in a hurry, the battery internal resistance will dictate how it wants to be charged. Once bulk and absorb are done, then you can work on EQ but some SG levels would dictate if EQ is even necessary. EQ will affect capacity if one is excessive with it.

You don't need a resistor, the 11A is just fine. I just finished capacity test on the worst pair of T105's, it didn't improve off the 165Ah it tested last time, but I did not go to EQ voltage levels. My other 2 pair are over 80% and close to 85% recovery. I have my work cut out for me on the worst pair, it may take some time at high voltage to bring capacity up or this might be all I can get from them.

 

[TOU47]

I have had several conversations with this gentlemen on other topics but not about these batteries specifically. That said, I notice he also reconditions these batteries specifically. While he is near St George Utah... he might be able to help you solve your issues? Best of luck!

Ethan: 801dash882dash3485
DC Solar Trailer Battery Recondition https://classifieds.ksl.com/listing/62327456

 

[shadowmaker]

The problem with high amps is it will boil the water, the problem you were trying to get away from. Leave the 12.5A charger on for a few days, it will reach absorb after bulk and the current will decrease while voltage will move closer to the 31V. The 31V will actually work well for desulphation, it takes longer than charging at EQ levels above 32V which would be above 2.65V per cell for EQ, but is still effective, keeps battery temp low and water consumption down. I wouldn't get in a hurry, the battery internal resistance will dictate how it wants to be charged. Once bulk and absorb are done, then you can work on EQ but some SG levels would dictate if EQ is even necessary. EQ will affect capacity if one is excessive with it.

You don't need a resistor, the 11A is just fine. I just finished capacity test on the worst pair of T105's, it didn't improve off the 165Ah it tested last time, but I did not go to EQ voltage levels. My other 2 pair are over 80% and close to 85% recovery. I have my work cut out for me on the worst pair, it may take some time at high voltage to bring capacity up or this might be all I can get from them.

Today had to pull out almost 50-150ml acid out of those cells as it seems to expand during charging. Will keep that acid and when cells need a refill next time, I'm going to use this acid instead of water.