One cell dead but voltage not Dropping below 12volts, How??

[vivekgangwar02]

Hi,
greetings!My 12volts 35Ah car lead acid battery was sitting too long and I found it with just zero charge left around 5 6 volts. I peeked into it and saw the cell near to the negative terminal has some white deposits in it, probably it is sulfation (90% sure).
The battery is 30+ months old now. I put the battery on charging with a cheap transformer based charger. I put it on charge for about 48 hours continously.
while the five cells were keep on boiling, but the sixth cell didnt show any movement in the electrolyte inside i.e. it doesnt bubble.
Another thing to note about the charger is, while this process the total voltage of the battery went to 14.75 volts. The Specific gravity of the five of the cells rose from nearly nothing to 1.260 and while the sixth cell didnt had any improvement in this.
I tried adding 1.190 concentrated solution to the cells, and again I tried monitoring, the specific gravity didnot rise a bit.

My concern is if a single cell is not charging, then how the battery is putting itself up at more than 12 volts? (12.2- 12.5 precisely).
I even tried cranking my car up and it worked, I tried monitoring the voltage while cranking and it went to 10.2 volts while doing that.

I am not sure what is happening here, so I am unable to decide if I should replace the battery or should I try reviving it by any other means? I have a solar mppt system installed at my home, should I try charging it with high current? what sense it will make as the other cells are already at their maximum specific gravity?

Thank You in advance.

 

[sunshine_eggo]

You simply have a weak and/or failing cell. The battery should be replaced before it strands you somewhere.

 

[Zwy]

Most likely the connection internally for the cell has deteriorated/high resistance. Measuring open circuit voltage you see the 12.2-12.5V but when a load is placed on the battery, the voltage drops to 10.2V. Eventually the connection will fail entirely.

The other possible fault is the one cell is severely sulfated and the chemical reaction is limited or plate material is laying on the bottom. If you have an adjustable power supply a voltage higher than 14.75 volts can be applied. Some modern smart chargers do this, commonly see charging voltages of just over 16V. You don't necessarily want current, it creates heat which can be helpful to expand plates and crack off hard sulfation but too much heat is detrimental to the plates. The inverter DC welder trick works because output voltage at a battery will be around 18V. This helps blow sulfation off the plates. One needs to remember however the plate material removed to expose fresh lead will reduce capacity and eventually all the sulfated lead from the plates ends up on the bottom of the battery and battery capacity is severely reduced.

You could try a higher charging voltage but be prepared this battery may not recover.

 

[vivekgangwar02]

Most likely the connection internally for the cell has deteriorated/high resistance. Measuring open circuit voltage you see the 12.2-12.5V but when a load is placed on the battery, the voltage drops to 10.2V. Eventually the connection will fail entirely.

The other possible fault is the one cell is severely sulfated and the chemical reaction is limited or plate material is laying on the bottom. If you have an adjustable power supply a voltage higher than 14.75 volts can be applied. Some modern smart chargers do this, commonly see charging voltages of just over 16V. You don't necessarily want current, it creates heat which can be helpful to expand plates and crack off hard sulfation but too much heat is detrimental to the plates. The inverter DC welder trick works because output voltage at a battery will be around 18V. This helps blow sulfation off the plates. One needs to remember however the plate material removed to expose fresh lead will reduce capacity and eventually all the sulfated lead from the plates ends up on the bottom of the battery and battery capacity is severely reduced.

You could try a higher charging voltage but be prepared this battery may not recover.

Okay, thanks I have a mppt, the battery is 35Ah, how much current do you think I should provide it? I can take it to 16volts using it. Although I tried connecting it directly to a 60watt 20volts solar panel for 2 3 hours and the last cell didnt improve.
and what do you think for how much time I need to do it so it happens? I can try 10amps at 160watt.

but when a load is placed on the battery, the voltage drops to 10.2V.

I believe on cranking it takes more than 300amps from the battery right? so it should happen.

 

[vivekgangwar02]

You simply have a weak and/or failing cell. The battery should be replaced before it strands you somewhere.

Thankyou for your response,
I expected much more info from you on why that's happening, how could only 5 cell battery provide such a high cranking current to start the engine?

anyways, is there any ways I can recover it? can I put it on solar mppt at 16volts 10A?

 

[sunshine_eggo]

Thankyou for your response,
I expected much more info from you on why that's happening, how could only 5 cell battery provide such a high cranking current to start the engine?

You can expect all you want. I have no obligation to tell you what you want to hear even when you pester me personally.

It's a 30 month old battery that has been abused and is showing overwhelming signs of degradation. Starter batteries are relatively fragile compared to deep cycle batteries and are easily damaged by neglect/abuse.

anyways, is there any ways I can recover it? can I put it on solar mppt at 16volts 10A?

You can do anything you want. Unfortunately, you've already screwed up by adding acid.

I am not sure what is happening here, so I am unable to decide if I should replace the battery or should I try reviving it by any other means? I have a solar mppt system installed at my home, should I try charging it with high current? what sense it will make as the other cells are already at their maximum specific gravity?

You should just replace it. I've attempted to recover starter batteries multiple times, and had seemingly good success with full SG and voltage recovery; however, they were very short lived with a catastrophic cell failure shortly after putting back into service.

 

[vivekgangwar02]

You can do anything you want. Unfortunately, you've already screwed up by adding acid.

I added mixed solution because I heard the sulfuric acid gets crystallizes with lead to form crystals, so charging not* happening due to that.

I was confused if I should add distilled water to make it dissolve or acid to make it charge :/

I want to revive it because I dont want to return it to service guys for a low replacement value, rather I will use with something else and sell it when it becomes junk.

 

[vivekgangwar02]

You should just replace it. I've attempted to recover starter batteries multiple times, and had seemingly good success with full SG and voltage recovery; however, they were very short lived with a catastrophic cell failure shortly after putting back into service.

I tried connecting it to my mppt, but only supports equalize upto 16.5volts, bulk 16.5volts and float at 15.5 volts.

when I put it on charge, it quickly reached 16.5 and came to float 15.5volts as charging current was high.

but in this process I notices that the dead/weak cell starts bubbling. So I thought lets give it a try.
1. What I did is for the rest five cells which were good I replace half of their electrolyte with distilled water, assuming they wont be destroyed/over charged in the further process. have I done right?
2. Can you please tell me what affect of the electrolyte concentration makes on the charge process? based on this I have two options to do:

• Keep the acid concentration low in the five good cells and high in the weak/bad cell.
• Keep the acid concentration low in the one weak cell and high in the five good cells.
  What do you suggest? @sunshine_eggo @Zwy . Your responses are very much appreciated.

 

[Zwy]

Okay, thanks I have a mppt, the battery is 35Ah, how much current do you think I should provide it? I can take it to 16volts using it. Although I tried connecting it directly to a 60watt 20volts solar panel for 2 3 hours and the last cell didnt improve.
and what do you think for how much time I need to do it so it happens? I can try 10amps at 160watt.

Use the lowest amps to maintain the high voltage. Time is your friend. Amps are the enemy, any excess amps just turns to heat.

I believe on cranking it takes more than 300amps from the battery right? so it should happen.

Battery should have a CCA rating. Use a carbon pile to put the CCA load on the battery for 10 seconds. Take the reading from carbon pile and it needs to be adjusted for battery temp.

That is how a battery should be load tested. I can take a used car battery that fails a load test and put it in my lawn mower and it will crank the mower engine over just fine for a few years. It's all about load and load rating.

 

[vivekgangwar02]

I tried connecting it to my mppt, but only supports equalize upto 16.5volts, bulk 16.5volts and float at 15.5 volts.

when I put it on charge, it quickly reached 16.5 and came to float 15.5volts as charging current was high.

but in this process I notices that the dead/weak cell starts bubbling. So I thought lets give it a try.
1. What I did is for the rest five cells which were good I replace half of their electrolyte with distilled water, assuming they wont be destroyed/over charged in the further process. have I done right?
2. Can you please tell me what affect of the electrolyte concentration makes on the charge process? based on this I have two options to do:

• Keep the acid concentration low in the five good cells and high in the weak/bad cell.
• Keep the acid concentration low in the one weak cell and high in the five good cells.
  What do you suggest? @sunshine_eggo @Zwy . Your responses are very much appreciated.

@Zwy did you check this? Thanks.

 

[Zwy]

@Zwy did you check this? Thanks.

I wouldn't mess with the electrolyte, just make sure the plates are covered. Do not fill cells full as the electrolyte will expand from heat and also bubbles from hydrogen and oxygen.

If the cell is bubbling, continue on your way and keep an eye on battery temp and electrolyte level. If it exceeds 110F, then quit charging and let it cool down. Keep checking specific gravity. I use a hydrometer, I don't trust floating ball testers as they are totally inaccurate. If specific gravity comes up, then keep charging until the specific gravity of the cells is basically equal. If it doesn't get there, most likely the cell has failed.

Nothing wrong with what you are doing concerning attempts to recover. You learn much in the process. I recently recovered 4 T105 Trojans left for dead to over 90% capacity, I've been using the batteries in my golf cart all summer. Starting batteries are different with thinner and more plates to give the higher CCA required. Your attempt may be a failure as far as recovery but hopefully you learn something in the process.

 

[Zwy]

As far as electrolyte concentration, the battery was built with the correct electrolyte composition. The sulfuric acid will combine with the lead during discharge to make lead sulfate, that is how electrons are released. The charging process reverses the process. Over time, lead sulfation will build up on the plates and acid will not make good contact with the plates in order for the chemical reaction to take place. The idea behind equalization charge at higher voltages is to remove that sulfation, either by reversing the chemical process or blowing the sulfation off the plate so new lead material is exposed. There is no reason to attempt to change electrolyte composition.

 

[vivekgangwar02]

I wouldn't mess with the electrolyte, just make sure the plates are covered. Do not fill cells full as the electrolyte will expand from heat and also bubbles from hydrogen and oxygen.

If the cell is bubbling, continue on your way and keep an eye on battery temp and electrolyte level. If it exceeds 110F, then quit charging and let it cool down. Keep checking specific gravity. I use a hydrometer, I don't trust floating ball testers as they are totally inaccurate. If specific gravity comes up, then keep charging until the specific gravity of the cells is basically equal. If it doesn't get there, most likely the cell has failed.

Nothing wrong with what you are doing concerning attempts to recover. You learn much in the process. I recently recovered 4 T105 Trojans left for dead to over 90% capacity, I've been using the batteries in my golf cart all summer. Starting batteries are different with thinner and more plates to give the higher CCA required. Your attempt may be a failure as far as recovery but hopefully you learn something in the process.

Sadly, I couldn't recover it, I did not have enough time to disconnect my house from mppt and connect it to the battery. I connected it to a 100watt panel directly at someone else's house, it may recover but could take so many days to do so.

Also I had an idea in mind that the way we measure the voltage across cells, we can also charge them. unluckily I do not have some lead rods in my house because I cant dip wires in the electrolyte and try charging a cell directly. It will quickly dissolve in it if I use any metal except lead, not sure on this but probably we can easily charge a single cell without affecting others.

I also tried discharging and recharging the battery, and it went down quickly. Conclusion: Not trying anymore now.
ThankYou

 

[Substrate]

You should just replace it. I've attempted to recover starter batteries multiple times, and had seemingly good success with full SG and voltage recovery; however, they were very short lived with a catastrophic cell failure shortly after putting back into service.

I'm with you! Most recovery efforts are a waste of time, or worst of all, scams to hijack the proper recycling stream. Better not to let it get like that in the first place.

Grandma told me that when putting aspirins in each cell, that Advil worked better than Bayer.