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Need Advice on Equalization and Battery SG (unusual)

LuckyLuke

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Jan 30, 2022
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Hi people this is my first post on this forum, I'm hoping for some better insight into my issue since the specifics of my problem are nowhere to be found online or in battery manuals.

I recently bought two deep cycle flooded 12v 260ah batteries for my 24v system four months ago. When under moderate use I noticed the voltage would deplete very quickly to under 23v while the SG readings were over 1.260 in each cell. During the weeks I was scratching my head as to why this was happening and it was driving me insane until I ordered 2 proper glass hydrometers [1.100 - 1.300] since I was unsure of the plastic hydrometer I was using. After they new hydrometers arrived I tried and tested them and they were not giving any readings on these batteries, the complete float was resting under the water line, I thought I got ripped off so I ordered another glass one... The new one arrived and the same thing happened! Then the alarm bells rang in my head, I quickly went and tested all these hydrometers on a spare 12v car battery and discovered they all work perfectly and got a good 1.280 reading. The plastic hydrometer I was using was useless.

I am quite convinced that the shop I bought these batteries from were never put through a commission charge and we're sold with an SG close to 1.050, judging by the faulty hydrometer I had been using, and a time where I asked the salesman about hydrometers (he had no clue what they were or its use) let alone the absence of them in the shop. I assume that the employees filled the battery cells in a dry state with distilled water, charged the batteries for a few hours and thought it was good enough for customers...

Anyway, the batteries hit absorption phase (29.6v) for 3h nearly every day since I have had them so they had been getting a lot of charge. Another thing to note is that the cells look in great condition and do not have any visual signs of sulfation

My Goal now is to raise the SG to at least 1.260. So about 5 days ago I have been equilizing these batteries in series at 32v - 33v at 4 - 5 hour intervals with slow steady success. The total time spent on EQ is around 24 hours, the SG has risen and plateaued at 1.200 at 27° celsius from basically near nil acidity. The highest temp during these charges was 32° celsius. The bank is sitting at a very stable 24.4v now (SG 1.200) which I had never observed before the process was started.


The questions I would like to ask:

1# Should I stop the EQ charge and cycle the batteries for a day or two before I continue further equilizing, if the SG readings have plateaued for 2 hours during EQ?

2# Was sulfation even possible if the batteries never had an acid density anywhere near 1.100 in it's life?

3# Have you had experiences where you have had SG plateaus while equalizing before, and what is you advice on dealing with it?

4# If the batteries were cycled with such a low SG, do the cycles even count since I wasn't using the full capacity of the batteries?

5# Has the break in period even started after what has happened? I have heard that with wet lead acids they take around 90 cycles to achieve full working capacity.

Thanks for bearing with me,

Luke

IMG_20220131_161323.jpg

Edit:

24v system 260ah, 2 x 12v batteries

After 24h of EQ charging at 32v - 33v the batteries are still accepting 22 amps but SG is stuck on 1.200
 
Last edited:
Hi people this is my first post on this forum, I'm hoping for some better insight into my issue since the specifics of my problem are nowhere to be found online or in battery manuals.

I recently bought two deep cycle flooded 12v 260ah batteries for my 24v system four months ago. When under moderate use I noticed the voltage would deplete very quickly to under 23v while the SG readings were over 1.260 in each cell. During the weeks I was scratching my head as to why this was happening and it was driving me insane until I ordered 2 proper glass hydrometers [1.100 - 1.300] since I was unsure of the plastic hydrometer I was using. After they new hydrometers arrived I tried and tested them and they were not giving any readings on these batteries, the complete float was resting under the water line, I thought I got ripped off so I ordered another glass one... The new one arrived and the same thing happened! Then the alarm bells rang in my head, I quickly went and tested all these hydrometers on a spare 12v car battery and discovered they all work perfectly and got a good 1.280 reading. The plastic hydrometer I was using was useless.

I am quite convinced that the shop I bought these batteries from were never put through a commission charge and we're sold with an SG close to 1.050, judging by the faulty hydrometer I had been using, and a time where I asked the salesman about hydrometers (he had no clue what they were or its use) let alone the absence of them in the shop. I assume that the employees filled the battery cells in a dry state with distilled water, charged the batteries for a few hours and thought it was good enough for customers...

Anyway, the batteries hit absorption phase (29.6v) for 3h nearly every day since I have had them so they had been getting a lot of charge. Another thing to note is that the cells look in great condition and do not have any visual signs of sulfation

My Goal now is to raise the SG to at least 1.260. So about 5 days ago I have been equilizing these batteries in series at 32v - 33v at 4 - 5 hour intervals with slow steady success. The total time spent on EQ is around 24 hours, the SG has risen and plateaued at 1.200 at 27° celsius from basically near nil acidity. The highest temp during these charges was 32° celsius. The bank is sitting at a very stable 24.4v now (SG 1.200) which I had never observed before the process was started.


The questions I would like to ask:

1# Should I stop the EQ charge and cycle the batteries for a day or two before I continue further equilizing, if the SG readings have plateaued for 2 hours during EQ?

2# Was sulfation even possible if the batteries never had an acid density anywhere near 1.100 in it's life?

3# Have you had experiences where you have had SG plateaus while equalizing before, and what is you advice on dealing with it?

4# If the batteries were cycled with such a low SG, do the cycles even count since I wasn't using the full capacity of the batteries?

5# Has the break in period even started after what has happened? I have heard that with wet lead acids they take around 90 cycles to achieve full working capacity.

Thanks for bearing with me,

Luke
Luke,


Were the batteries used? What is the A/H rating of your 24 volt system? How deep of a discharge do your batteries normally experience daily?

To be accurate I have a 1500A/H 48 volt solar forklift battery that are discharged about 25% daily (still 75% left in battery). I absorb charge them for 58.8 volts for 2.5-3 hours daily and when I EQ them, I EQ them at 62.5 volts for 2 hrs and they return to SG 1.30 1.31
Your volt values should be half of mine cause you have a 24 volt system. Also, for checking SG look at amazon for a refractor type SG checker made for battery acid. They're cheap.....22-30 dollars and we soooooo much easier.

You should EQ your batteries ONLY after they are fully charged to SG 1.275. I would EQ them at 31 VDC for 2 hrs and see what effect that has on your batteries SG.? My batteries never rise above 90 degrees F during a EQ cycle.

My batteries seemed to achieve full capacity after 1 year of service.

If your batteries were used, they maybe sulfated. Most industrial batteries are abused when used in warehouses. They are not watered properly, they are not charged properly, for this reason, I would be VERY skeptical of buying used FLA batteries.

There is a lot of ideas opinions what a "battery cycle" is. I only have to charge the top 25% of the battery daily....so for me, every 4 days is 1 cycle. I have had my batteries for 5 years (1825 days) and see no degradation. I dont honestly know how long they will last, but my batteries are not abused, are watered when needed (every other month) and charged to 1.30-1.31 at least twice a week.

If you have any questions let me know. Good luck

Homeskillet
 
Luke.....is your total system only 260A/H @ 24VDC? Only 2 12volt batteries?
Thanks for your reply. Yes the total system is 260ah at 24v, two new 12v batteries. I like your recommendation about the SG refractometer, I will check that out.

The batteries were being fully charged at 29.6v (absorb) for 3 hours and then entering float 5 days a week during these 4 months using them. After all of that charging, the SG was still below 1.100 tested with my newer hydrometer. It almost seemed like there was a complete disconnect between the voltage and the SG hence why I think they were never commissioned properly.

Since using them I never discharged them below 40% voltage-wise.

The battery voltage is really stable under load after the equilization charges which is a relief. The bank is still technically at 50% charge at 1.200, but at least now the voltage matches the SG reading.

Should I cycle the batteries normally for a while so they rest or continue equalizing to get readings up to 1.260 - 1.280?
 
OK.....your system is equal to 130 AH at 48 volts. My system is over 10 times the capacity. That isn't meant as a dig,,,,,just a fact. What are you running with this system. I run a 2500 square foot house.. with a wood pellet stove and a couple of propane heaters (very low wattage to heat house) My system uses about 350- 400A/H daily....even only using the top 25 % of the battery. Is your system undersized? I ask this because....if I discharge my batteries to 50% (which i do occasionally)......they require a lot more and 2.5 hours at absorb voltage to reach full charge. Maybe you dont run a whole house on your system. Maybe we are talking apple and oranges?
 
OK.....your system is equal to 130 AH at 48 volts. My system is over 10 times the capacity. That isn't meant as a dig,,,,,just a fact. What are you running with this system. I run a 2500 square foot house.. with a wood pellet stove and a couple of propane heaters (very low wattage to heat house) My system uses about 350- 400A/H daily....even only using the top 25 % of the battery. Is your system undersized? I ask this because....if I discharge my batteries to 50% (which i do occasionally)......they require a lot more and 2.5 hours at absorb voltage to reach full charge. Maybe you dont run a whole house on your system. Maybe we are talking apple and oranges?
I have an electric dryer and and a electric oven and electric stove (go ahead and shoot me...i deserve it). I say that because trying to charge the battery daily in the winter....and running the dryer...and oven and stove, can be be very challenging. Are you trying to run a whole house?
 
I don't don't use more than 1500watt hours per day as this system is powering a small off grid house; low wattage fridge and tv. Never the less it's still very small power usage compared to you haha. Hey if you can away with running electrical heaters and stoves then why not! Especially in stable weather.

For heating I use a log burner and for hot house water I installed a rapid water heater that runs on propane gas which the washing machine is connected to with a valve that only allows hot water on the first cycle so the heating element doesn't turn on which uses 1800w of power (which i don't want). The water pump is automatic but hardly turns on unless pipe pressure drops below 15psi, that uses 600w.

I get your point about resistance relationship with discharge and charging. The only thing I can do is just give updates for now since these batteries are behaving differently now.

The odd behavior I noticed when my batteries were first bought was the insane quickness of charging to absorb voltage when they had been discharged 50% and very quick discharge under 100w load.

Now the voltage is behaving normally and correlates with the SG readings.
 
I have an electric dryer and and a electric oven and electric stove (go ahead and shoot me...i deserve it). I say that because trying to charge the battery daily in the winter....and running the dryer...and oven and stove, can be be very challenging. Are you trying to run a whole house?
I bought a kill a watt meter and ah meter because I'm conservative with power in general, so I have measured the off grid house consumption though these instrument.
 
Hi Luke,

I run electrical heaters. I did today. It was severe clear and my solar array made 66kwh. 30 kWh went to recharge the batteries and 36 went to the 4 ea 1500 watt heaters and a 6000 watt dryer. Normally i use 26KWH daily (about a constant 1100 watt draw). without dryer or electric heaters being used.

When my 48 volt 1500 A/H batteries are fully charged to 1.30 SG & (after the sun is down. no charging going on)......if I turn on the dryer....6000 watt draw, my battery voltage will drop to 47 volts. (23.5 volts if it were a 24 volt system) . After dryer shuts off, the voltage jumps to 50.3.

I know that battery voltage is supposed to be taken with no load on battery for 24 hrs.............That is not feasible for a off grid user when its 7 below zero.....lol.
 
Luke.....lets compare apple and apples. Please bear with me. My home, no matter the size, has a energy star fridge and freezer and LED lights. I have a pellet stove that draws 120 watts and propane heaters that draw 26 watts. I have a heat pump type hot water heater. Even If i dont use my electric stove or dryer or oven, i still use 23KHW daily.....thats equivalent to a constant (950 watts X 24 hours) draw on the system. If your system was to perform like mine (being 10% of my system).....you could only draw 95 watts/hr over a 24 hr period. I cant wrap my ahead around only pulling 95 watts continually....... If i am wrong, I apologize, Do you know how many KWH, you use daily?
 
Luke.....lets compare apple and apples. Please bear with me. My home, no matter the size, has a energy star fridge and freezer and LED lights. I have a pellet stove that draws 120 watts and propane heaters that draw 26 watts. I have a heat pump type hot water heater. Even If i dont use my electric stove or dryer or oven, i still use 23KHW daily.....thats equivalent to a constant (950 watts X 24 hours) draw on the system. If your system was to perform like mine (being 10% of my system).....you could only draw 95 watts/hr over a 24 hr period. I cant wrap my ahead around only pulling 95 watts continually....... If i am wrong, I apologize, Do you know how many KWH, you use daily?
It's definitely under 1.5kw per day and that's including:

20w constant standby use from the inverter

20% possible power losses from batteries, system efficiency, and wiring.

Power usage:

Small fridge - 60 watts (compressor works 50% of the time)

LED lighting - 9 to 18 watts total only at night

Water pump - 600w (5% active during 24h period, 20 second interval )

LED TV - 40w - (used 20% of the day)

At a time before using these flooded batteries I was using two deep cycle AGM batteries 140ah as 24v [two 12v], I never had any problems with them what so ever except on cloudy days I would disconnect them when they were 50% discharged to avoid long term damage. I upgraded to these new flooded lead acids so I can last longer without sun, and have had problems. The other AGMs I had are being used elsewhere and are in healthy condition.

Regardless of the shop selling uncharged batteries, the problem lied in the faulty tester I was using and that I had no idea that I was using the two 260ah at a very low SG (I could of adjusted the charging parameters if I knew). I'm going to let the seller of the faulty hydrometer know that they might be responsible for destroying my new bank...

I'm just hopeful that all this time while I was using the 260AHs that the battery plates didn't sustain any hard sulfation damage due to the fact there was very weak acid in the cells.
 
I forgot to mention that I have a 1000w array that is over the 10% charging requirement for the 260AHs.
 
Luke.....lets compare apple and apples. Please bear with me. My home, no matter the size, has a energy star fridge and freezer and LED lights. I have a pellet stove that draws 120 watts and propane heaters that draw 26 watts. I have a heat pump type hot water heater. Even If i dont use my electric stove or dryer or oven, i still use 23KHW daily.....thats equivalent to a constant (950 watts X 24 hours) draw on the system. If your system was to perform like mine (being 10% of my system).....you could only draw 95 watts/hr over a 24 hr period. I cant wrap my ahead around only pulling 95 watts continually....... If i am wrong, I apologize, Do you know how many KWH, you use daily?
I understand what you are saying. What do you think could be the issue that under regular charging [bulk 30amps], [absorption 14.8v per battery absorbtion] and [13.8 per battery float] no one is in the house during the day so no power usage. The electrolyte is bubbling like normal and there is no discolouration, it's mostly sunny where I live... Wiring is flush and tight and there is no resistance from the panels to the batteries. Is my Epever CC a fake? I could swap the charge controller as i have another 2 in the shed and see what happens.

I had a SRNE controller that blew up from a surge, but I replaced and soldered all of the damaged voltage-control MOSFETS and it works like new now so I will try with that one, the other CC is a POWMR 60A.
 
Luke,

I owe you an apology and more than that, I am impressed. How low does your battery normally discharge. Is it normally discharged 70% with a 30% charge left.
 
Luke,

I owe you an apology and more than that, I am impressed. How low does your battery normally discharge. Is it normally discharged 70% with a 30% charge left.
It's fine, no offense taken.

With my previous AGMs rarely I discharged to 70% DOD but that's it. With these current ones I have I take great care not to discharge below 50% as the seller stated.

What crossed my mind was the capability of the array charging the bank, but the array meets the 10% rule. I have got up to 33amps with the system. It's connected as follows: 2 series strings, 1st string 3 × 160w panels and 2nd string 3 × 180w panels. I understand the mismatch and loss of 60w but hey I bought them at a good price. The Vmp is 68v and Imp is 14.1 amps = 958w which is ok considering 6 × 160w = 960w.

Update:

Voltage was stable all night sitting at 24.4 under moderate load, SG was sitting at 1.180.

Today I continued EQ charging for 3 hours at 32v after a couple of hours of absorbtion 29.6v. The SG had risen to 1.210 which was a first. Tomorrow I will continue the same procedure, if the SG doesn't rise after 60mins of EQ charging then I will immediately stop the process and continue another day.
 
It seems to me.....like that batteries refuse to take a charge. They show the proper voltages (which means little) but the SG (which means EVERYTHING) shows a totally different story. Can you slave in 2 other batteries (known good batteries) to see how they perform?
 
It seems to me.....like that batteries refuse to take a charge. They show the proper voltages (which means little) but the SG (which means EVERYTHING) shows a totally different story. Can you slave in 2 other batteries (known good batteries) to see how they perform?
Sure good idea, I will check with another spare to rule out if it's a fault in the wiring/connections, controller or panels, possibly breakers if they have an unknown resistance.
 
It seems to me.....like that batteries refuse to take a charge. They show the proper voltages (which means little) but the SG (which means EVERYTHING) shows a totally different story. Can you slave in 2 other batteries (known good batteries) to see how they perform?
I tested the system on another battery and it charged with no problem whatsoever so there are no issues with the PV array, CC, and wiring.

I think I found the issue! These batteries I have are semi industrial or you would say a "stationary" battery, the space between the cell opening hole to the plates is quite a large distance...

I followed a general trojan battery manual that states to top the battery up with distilled water up to 3/4 inch below the opening hole of every cell. Today I thought about the amount of distilled water I put in to my batteries every month, the water was sitting above 3 inches or more above the plates. No wonder the battery had a hard time charging and converting water to acid, I diluted the electrolyte that much that I reduced the battery's performance by 90% like an idiot.

I sucked about 8 liters of electrolyte from the two batteries until the electrolyte sat about half an inch above the plates in all cells. I started the equalization again from the last two hours of sun I had, and BOOM! The SG started to rise very quickly to just under 1.225! And then the sun had set quickly after that, so I will continue tomorrow. Voltage is steady at 24.6v (12.3v) under light to moderate load, no surface charge.

There is no manual for my 260AHs so I had no idea of the water/acid ratio of this battery, didn't even have a water line for watering so I conducted a watering maintenance routine from another manual (trojan) which I thought would be of similar internal structure and space. Boy was I wrong and just goes to show how important the water acid ratio is, too little or too much can have a negative effect on your bank.
 
Any updates on this? I have been going through battery problems and i cant get my SG high, I to properly added 2L of water to each battery a few months ago because they where covering the plates but not full. And to top it all off a few weeks ago when i got a new battery and i checked the levels to see if them covering the plates but very low and topped it up aswell! My batteries are like you describe 'semi industrial'. I am going to give a go taking some water out to see or EQ for a long time to evaporate enough.
 
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