Recovering a Lead Acid battery after it has been deeply discharged

[T1 Terry]

There have been a lot of threads about flat 12V aux batteries and a bit of mythical knowledge coming from the dealers and most definitely from who ever wrote the 12V maintenance software .... clueless comes to mind .....

A bit of preamble from another thread here Replacement 12V auxiliary battery for MGS5 .... so if you have already suffered through that, you can skip through to the next bit ... or look for something that won't bore you to tears or send you to sleep.

A lead acid battery needs to remain at charging voltage, above 13.6v min, to actually recharge. 13 .6v will maintain the charge at 100% if it is already at 100%, it will bring a battery up to about 50% SOC if it stays at that voltage for 24 hrs or more, but that is no enough voltage to over come the inherent internal resistance of any type of lead acid battery.

Now, if the battery was not saturation charged when built, it will already begin sulphating ..... within 12 hrs actually .....

If the terminal voltage is held at 14V for 12 hrs or more, you can get closer to fully charged, as long as the plates are not sulphated. Once the sulphation starts on lead acid plates, no chemical reaction can occur in that part of the active plate, so capacity is lost.

The only way to remove sulphation is with a pulse charge, higher than 16.5v but very short bursts. This forms very small bubbles within the lead plate that gradually push the sulphur out of the lead ..... As long as it hasn't been there for too long, it will return to the electrolyte and increase the specific gravity of the sulphuric acid ..... if it has been there long enough to bind with the surface of the lead plate, it will flake off and drop to the bottom of the cell electrolyte reservoir ... harmless until it build up enough to reach the bottom of the plates, then it shorts the plates out and you get that sudden dead cell ......

Naturally, this reconditioning pulse charging can't happen when the terminals are connected to any appliance, this includes the vehicle's 12V system, so the battery at minimum must have the negative terminal disconnected. ... I'll explain in another post why the negative terminal should be the first off and the last connected at the end ... If I remember

There are a few quality chargers that can have a reconditioning or de-sulphation cycle engaged, it takes quite a while, the longer it has been sulphated, the longer it will take to de-sulphate .......
C-Tek is a well known brand that has a de-sulphating cycle, you can buy or even build your own, this came up on Google search How to Restore Sulfated Batteries | Battery Chargers but I am not in anyway endorsing them, I've never used any of their products, but there are heaps out there .....

T1 Terry

 

[Black estate]

Yep my brother has a battery reconditioner charger and when I got my MG5 I took the 12V bat off and done it and it's good as gold now.

 

[stevedee]

There have been a lot of threads about flat 12v aux batteries and a bit of mythical knowledge coming from the dealers and most definitely from who ever wrote the 12v maintenance software .... clueless comes to mind ...

T1 Terry

Hi T1 Terry.

I'm not a lead-acid battery specialist, so hope you won't rip-my-head-off if I ask clueless questions or appear to challenge any of your points.

1) it sounds like your comments above relate to traditional, flooded, lead-acid batteries ...pls clarify
2) for an EV, a traditional 12V battery (which is great for short duration, deep discharge operation) is a poor choice.
3) for an EV, AGM batteries have more suitable characteristics.
4) charging & maintained SoC for AGM differ from Trad batteries; AGM should not be fully charged, but perform & have a longer life with PSoC.
5) from what [I think] I understand, the way my S5 is treating its AGM 12V battery is consistent with best practice; e.g. lightly (PSoC) recharging the battery from the traction battery when terminal voltage drops to ≤ 12Volts. Since traction battery has almost 2000 times the capacity of the system 12V battery, the car should remain 'healthy' even if left 'parked up' for several months, assuming the car was initially charged to (say) 80%.

Any comments so far?

I got AI to compile a comparison of traditional flooded 12V (ICE) batteries with ev 12V AGM.

Probably too much to paste, so attached as a pdf.

From the table of typical SoC % for terminal voltage, it looks like my S5 is trying to keep its AGM battery between 30% - 80/85% approx (12.0V to 12.7V).

This is pretty much what I do with my phone: 20 - 85%. ...different battery technology, but for similar reasons.

 

[T1 Terry]

Sorry, this turned into a long post and I did try to only touch on each part ....

I was taught "there is no such thing as a silly question" when I was doing my Cert 4 training and assessment course .... I gotta tell you, I've had some training sessions where participants challenged that idea but this isn't one of them, so you can breathe easy

Maybe an explanation of the types of lead acid batteries might help answer these questions ..... The first one, there are start batteries and there are deep cycle lead acid batteries, some claim to combine the two and call them marine batteries, unfortunately, they combine the worst sides of each type, not the best.
If you want me to explain how to tell them apart and how to desulphate each type, just ask ... I'm happy to bore people with information

I'm guessing by traditional lead acid you mean flooded cell.
These originally had a cap on each cell and the idea was to keep the electrolyte up to the little tangs that can be seen where the cap goes in .... even this fact isn't well known.

The next version of this was the Magic Eye or similar names, where there was a clear plastic removable cap with an indicator under it, I think:
Blue was OK
Red said the specific gravity was low and it needed charging
Clean meant it needed topping up with distilled water

The next version had a see through case so you could see the electrolyte level, but you had to peel the brand label off to find the filler caps

The latest version is "sealed battery" and has a vent tube out the side, when the electrolyte gets low .... there is nothing you can really do about it, possibly try injecting distilled water in the trough the vent tube and then put the end of the vent tube into a plastic drink bottle, you can use that the next time it needs the electrolyte topping up
These are the ones you referred to as best not to fully charged, the manufacture used the line that over charging was the cause on electrolyte loss .... a very handy distortion of the truth, desulphation and cell equalising does involve electrolysis where the water component breaks down into hydrogen and oxygen ..... that frantic bubbling seen in the cells of a removeable cap flooded cell battery when equalisation charging .....

The next upgrade was AGM (Absorbed Glass Mat) where limited electrolyte was used, the fibre glass mat held the electrolyte against the plates and the cells had a thing called a recombiner under where the cap went, and the use a catalyst to recombine the hydrogen and oxygen into pure water and drip it into the electrolyte
This idea works well when a battery is held at 14.4vdc for one type and 14.8vdc for the other type, I believe the higher voltage was for colder climates ..... This recombining unit generates heat, so does equalisation charging, so the 16.5vdc for equalisation was discouraged due to the heat generated by the recombiners adding to the heat generated by electrolysis ......
Unfortunately, this rapid bubbling also helped remix the concentrated acid in the bottom of the cell with the pure water being added in droplets to the top of the electrolyte from the recombiners ..... this unmixed electrolyte is known as stratification ..... the pure water at the top of the cell doesn't have any sulphur in it, so it can't chemically react with the lead, so it can't generate any electrical energy, while the concentrated acid in the lower part eats the lead acid plates away ..... so that bubbling charging voltage level being maintained is important to achieve this electrolyte mixing as well ....

The next brain child was gel cell battery. These hold the electrolyte in a gel format so are spill proof. They don't suffer stratification or electrolyte loss, sounds great, but the catch is, the charge rate and voltages need to be very carefully controlled.
Charged too fast and bubbles form between the gel and the plate, rapid discharge has the same affect. These bubbles are trapped, leaving an area where the gel electrolyte no longer comes in contact with the plates, each bubble is a tiny loss of capacity and therefore, a reduction in the charging absorption rate and discharging capabilities ... without generating more bubbles .... the death cycle .....

The last and latest is lead crystal batteries. These have crystalised electrolyte, they can be deeply discharged, but the capacity recovery regime is a serious procedure, requiring charging and discharging on a repeated cycle until the capacity is returned .... works great in the lab, hopeless in the real world.

T1 Terry

 

[Joningy]

Hi T1 Terry.

I'm not a lead-acid battery specialist, so hope you won't rip-my-head-off if I ask clueless questions or appear to challenge any of your points.

1) it sounds like your comments above relate to traditional, flooded, lead-acid batteries ...pls clarify
2) for an EV, a traditional 12V battery (which is great for short duration, deep discharge operation) is a poor choice.
3) for an EV, AGM batteries have more suitable characteristics.
4) charging & maintained SoC for AGM differ from Trad batteries; AGM should not be fully charged, but perform & have a longer life with PSoC.
5) from what [I think] I understand, the way my S5 is treating its AGM 12V battery is consistent with best practice; e.g. lightly (PSoC) recharging the battery from the traction battery when terminal voltage drops to ≤ 12Volts. Since traction battery has almost 2000 times the capacity of the system 12V battery, the car should remain 'healthy' even if left 'parked up' for several months, assuming the car was initially charged to (say) 80%.

Any comments so far?

I got AI to compile a comparison of traditional flooded 12V (ICE) batteries with ev 12V AGM.

Probably too much to paste, so attached as a pdf.

From the table of typical SoC % for terminal voltage, it looks like my S5 is trying to keep its AGM battery between 30% - 80/85% approx (12.0V to 12.7V).

This is pretty much what I do with my phone: 20 - 85%. ...different battery technology, but for similar reasons.

Hi again @stevedee , Just noticed your mention of AGM, I checked just this morning as a matter of fact and my S5 is definitely FLOODED and not AGM, it's not easy to see, because the info label is partially hidden by the battery strap which I had to push aside to read it.
I set up a full reconditioning charge this morning with my CTEK MXS5 after removing the negative lead as @T1 Terry has suggested.
I'd be very interested and surprised if you have an AGM and not a "flooded" as I have.

 

[Joningy]

Hi again @stevedee , Just noticed your mention of AGM, I checked just this morning as a matter of fact and my S5 is definitely FLOODED and not AGM, it's not easy to see, because the info label is partially hidden by the battery strap which I had to push aside to read it.
I set up a full reconditioning charge this morning with my CTEK MXS5 after removing the negative lead as @T1 Terry has suggested.
I'd be very interested and surprised if you have an AGM and not a "flooded" as I have.

Sorry, this turned into a long post and I did try to only touch on each part ....

I was taught "there is no such thing as a silly question" when I was doing my Cert 4 training and assessment course .... I gotta tell you, I've had some training sessions where participants challenged that idea but this isn't one of them, so you can breathe easy

Maybe an explanation of the types of lead acid batteries might help answer these questions ..... The first one, there are start batteries and there are deep cycle lead acid batteries, some claim to combine the two and call them marine batteries, unfortunately, they combine the worst sides of each type, not the best.
If you want me to explain how to tell them apart and how to desulphate each type, just ask ... I'm happy to bore people with information

I'm guessing by traditional lead acid you mean flooded cell.
These originally had a cap on each cell and the idea was to keep the electrolyte up to the little tangs that can be seen where the cap goes in .... even this fact isn't well known.

The next version of this was the Magic Eye or similar names, where there was a clear plastic removable cap with an indicator under it, I think:
Blue was OK
Red said the specific gravity was low and it needed charging
Clean meant it needed topping up with distilled water

The next version had a see through case so you could see the electrolyte level, but you had to peel the brand label off to find the filler caps

The latest version is "sealed battery" and has a vent tube out the side, when the electrolyte gets low .... there is nothing you can really do about it, possibly try injecting distilled water in the trough the vent tube and then put the end of the vent tube into a plastic drink bottle, you can use that the next time it needs the electrolyte topping up
These are the ones you referred to as best not to fully charged, the manufacture used the line that over charging was the cause on electrolyte loss .... a very handy distortion of the truth, desulphation and cell equalising does involve electrolysis where the water component breaks down into hydrogen and oxygen ..... that frantic bubbling seen in the cells of a removeable cap flooded cell battery when equalisation charging .....

The next upgrade was AGM (Absorbed Glass Mat) where limited electrolyte was used, the fibre glass mat held the electrolyte against the plates and the cells had a thing called a recombiner under where the cap went, and the use a catalyst to recombine the hydrogen and oxygen into pure water and drip it into the electrolyte
This idea works well when a battery is held at 14.4vdc for one type and 14.8vdc for the other type, I believe the higher voltage was for colder climates ..... This recombining unit generates heat, so does equalisation charging, so the 16.5vdc for equalisation was discouraged due to the heat generated by the recombiners adding to the heat generated by electrolysis ......
Unfortunately, this rapid bubbling also helped remix the concentrated acid in the bottom of the cell with the pure water being added in droplets to the top of the electrolyte from the recombiners ..... this unmixed electrolyte is known as stratification ..... the pure water at the top of the cell doesn't have any sulphur in it, so it can't chemically react with the lead, so it can't generate any electrical energy, while the concentrated acid in the lower part eats the lead acid plates away ..... so that bubbling charging voltage level being maintained is important to achieve this electrolyte mixing as well ....

The next brain child was gel cell battery. These hold the electrolyte in a gel format so are spill proof. They don't suffer stratification or electrolyte loss, sounds great, but the catch is, the charge rate and voltages need to be very carefully controlled.
Charged too fast and bubbles form between the gel and the plate, rapid discharge has the same affect. These bubbles are trapped, leaving an area where the gel electrolyte no longer comes in contact with the plates, each bubble is a tiny loss of capacity and therefore, a reduction in the charging absorption rate and discharging capabilities ... without generating more bubbles .... the death cycle .....

The last and latest is lead crystal batteries. These have crystalised electrolyte, they can be deeply discharged, but the capacity recovery regime is a serious procedure, requiring charging and discharging on a repeated cycle until the capacity is returned .... works great in the lab, hopeless in the real world.

T1 Terry

Very interesting @T1 Terry and thanks, on one part of the forum, I cant remember exactly which, you asked for my battery physical size, it's no particularly easy, but looks like 185 long x 160 wide x 170 high approx. dims.

BTW Terry, purely by coincidence as you posted elsewhere, I'm doing a full reconditioning charge of the puny 35Ah S5 12v flooded lead acid battery, using my CTEK MSX 5 charger, it's now up to stage 7, where it is pulse charging and currently measuring15.8v and presumably rising.

This is in readiness for being left at Gatwick airport for over 3 weeks next week.

 

[T1 Terry]

Very interesting @T1 Terry and thanks, on one part of the forum, I cant remember exactly which, you asked for my battery physical size, it's no particularly easy, but looks like 185 long x 160 wide x 170 high approx. dims.

BTW Terry, purely by coincidence as you posted elsewhere, I'm doing a full reconditioning charge of the puny 35Ah S5 12v flooded lead acid battery, using my CTEK MSX 5 charger, it's now up to stage 7, where it is pulse charging and currently measuring15.8v and presumably rising.

This is in readiness for being left at Gatwick airport for over 3 weeks next week.

That will be a good test to see if the problem is actually under charged and sulphated cells, or just a lack of capacity.

T1 Terry

 

[Joningy]

That will be a good test to see if the problem is actually under charged and sulphated cells, or just a lack of capacity.

T1 Terry

On reconnecting the 12V neg lead this morning, ignition still off, left off but unlocked overnight, there was quite a flash as I touched the lead to the neg battery post, that in my opinion is drawing more current than I'd be expecting, it may of course be correct as there will be at least a relay or two clunking into action.

I took a voltage reading with the neg terminal disconnected of 13.8 V, as soon as I re-connected the neg lead the voltage had dropped to 12.5 V, quite a drop in a few seconds.

I'm still suspecting some sort of abnormal leak and NOT just from my dash cam (now switched and not permanent live) as MG suggested.

 

[T1 Terry]

The spark is possibly charging capacitors, but could also indicate a constant load, the clamp meter set for DC amps would tell you how much is being drawn ....
It would be interesting to see if the current draw reduces if you delete the MG app from your phones ....
Each 0.1v drop below 12.8v at a C20 load, around 1.75 amps for a 35ah battery, indicates a loss of 6% capacity, but there is every chance the load was greater than 1.75 amps if it created a spark when connected .....

T1 Terry

 

[T1 Terry]

Another episode of boring crap about lead acid batteries.

The difference between starter batteries, deep cycle batteries and marine grade batteries

The starter or cranking battery is generally flooded cell, has multiple very thin plates and is designed to supply high amps for a short period.
This is referred to as C.C.A (Cold Cranking Amps) a measure of a fully charged new batteries ability to deliver the quoted number of amps @ 0*F for 30 second while staying above 7.5vdc ..... No idea what they considered would actually still operate as designed @ 7.5vdc, certainly not fuel delivery pumps, injectors, the computer or a spark in a modern engine .... Basically a useless number that only allows comparison between lead acid cranking batteries.

There also an RC rating (Reserve capacity) Again, a new fully charged battery, is the number of minutes the battery @ 80*F can deliver 25 amps until the voltage drops to 10.5vdc, enough to make a light bulb glow yellow, but at that voltage, not enough to do much else.

A starter battery or cranking battery, does not have an Ah capacity, if a manufacturer claims an Ah capacity on a starting or cranking battery, they are telling porkies.

A Deep Cycle battery can be flooded cell, AGM or Gel .... to claim a lead crystal battery as being deep cycle is a bit of a stretch of definition

They are built with thick lead plates and designed to deliver a C20 current for 20 hrs until flat ... even from brand new and fully charged, this is often down to 9vdc or less.

Because the lead plates are thick, they require slow charging for a long time, 12 hrs will get them from around 70% to around 90% SOC, more than 24 hrs to get to 98% SOC, days at 13.85v to 14vdc to get that last 2% in there. If you fast charge them from say 11v up to 14.4v, they might be up to 70% SOC, but if you stop there, the sulphur deep in the lead plate remains and gradually hardens till it can't be shifted, you then have a deep cycle battery with 70% of the advertised capacity.
C20 means the capacity in amps divided by 20 hrs, a fully charged as new 100Ah lead acid battery with a C20 rating will deliver 5 amps for 20 hrs, until the voltage is so low it can't really do anything much.
The rule of thumb is discharging to 50% SOC (a number that can be hard to determine because the battery capacity drops off after the first 10 cycles) but an as new fully charged 100Ah deep cycle battery should be able to deliver 5 amps for 10 hrs and still maintain 12v while supplying that 5 amps .....

That 50% SOC can be measured with a constant C20 load for 10 hrs .... if you get the whole 10 hrs, you have an as new deep cycle battery, if you get 9 hrs you have a battery at 80% of the advertised capacity .... all the way down to an hr, you have a door stop ......

A load exceeding that C20 current draw, is not available on a linear basis .... you can have 5 amps for 20 hrs from a 100Ah battery, but you can't have 100 amps for 1 hr, more like 20 mins absolute max and the battery is not much more than a door stop after that, the plates and separators would be buckled and the electrolyte near boiling .....

Then we have the Marine battery, not really a cold cranking battery, or a deep cycle battery. By physical size, it's a very poor performer for doing either job, so they are generally big batteries in physical size so they can deliver the CCA and anywhere near acceptable Ah capacity at a C20 rate.

T1 Terry

 

[Joningy]

I don't have a lot of time to do a current leakage (parasitic draw) test, or to delete the iSmart app for checks before we are away.

After reconnecting the neg terminal this morning, I had all sorts of warnings about various functions not working, I've got most of them back now after a full hard factory reset and reinstalling and setting up the iSmart app, I don't want to risk doing it again today, as it took a while to set everything up as I wanted, but now fully expecting to return to a flat 12v battery after 3.5 weeks sat in a car park.

As a boy scout moto from many years ago, "I'll be prepared" All the gear and NO idea springs to mind just a modicum actually, but as they say "a little knowledge is a dangerous thing" catch up soon I hope!

Shouldn't be needing to do any of this sh** MG, I hope you are following this thread, but YOU are causing a lot of people a lot of problems.

 

[T1 Terry]

The battery maintenance profile is woefully inadequate for a flooded cell start battery, without adding a maintenance charger to bring it up each day, the flat battery saga is going to continue unfortunately

T1 Terry

 

[OriginalBigAl]

T1 Terry , not boring at all , great informative posts.
Recently I have been playing around with some old batteries , mainly 20v lithium drill pack batteries.
I have two or three which have duff cells so are down to 16v and will not charge so I have pulled them to bits to try and make two good ones by cannibalising them . Success by the way .
I also have an old 100ah 12v battery from my van which holds voltage well but does not have enough humpf to start the van , but should have enough to get the car working should the need occur. This is presently sat at 12.6 v and for an experiment I connected a Drill pack 20 + volts to it , after a few seconds I heard fizzing and bubbling from the 12v battery. Quite alarmed I quickly disconnected the leads. Checking the voltage it was showing around 17 volts after 2 minuets which then very slowly started to drop. Would this unknowing experiment have started a de-sulphation cycle and could I carry on doing it intermittently to try to recover the 12v battery?
Because now I had a wrecked drill pack battery but with 3 decent cells ( 12.1 v ) when connected in series would it be possible to connect those to a "dead " or under voltage 12 car battery to get the car to fire up should again the worst happen . ( like an homemade battery booster pack ) one shot as I have no way to recharge it ...... yet! Thank you Professor .

 

[Lovemyev]

Hi again @stevedee , Just noticed your mention of AGM, I checked just this morning as a matter of fact and my S5 is definitely FLOODED and not AGM, it's not easy to see, because the info label is partially hidden by the battery strap which I had to push aside to read it.
I set up a full reconditioning charge this morning with my CTEK MXS5 after removing the negative lead as @T1 Terry has suggested.
I'd be very interested and surprised if you have an AGM and not a "flooded" as I have.

The 99$ question :-
Are we dealing with the "run of the mill, common or garden" flooded type battery.
Or the AGM type battery fitted straight from the factory then in the S5's in the U.K. ?.
If its the basic flooded type, the only wiggle room for improvement is a bigger capacity.
As long as the the battery tray can except one of course !.