Batteries Over Charging?

[steve.sharratt]

I have a Victron Multiplus 5000VA charging 2V traction batteries (24V).  I noticed today that the batteries were bubbling with a strong smell.  The Victron was saying Absorption but the Amps input was still around 25amps.  I disconnected from the shore power and checked the battery voltage and all were above 2v.  I left the inverter on (charger off) for the day and all seems well.  The batteries only dropped by 5% which I think is fair.  I reconnected the mains to recharge the batteries and I am now again in Absorption but still reading around 25amps in.  Note that the battery levels were recently checked and adjusted but they were at overflow today.  I drew out around 300ml per battery to get the levels back down. Has anyone come across this problem? I cant figure whether it is the Charger or the batteries.  

[Tracy D'arth]

5 minutes ago, steve.sharratt said:

I have a Victron Multiplus 5000VA charging 2V traction batteries (24V).  I noticed today that the batteries were bubbling with a strong smell.  The Victron was saying Absorption but the Amps input was still around 25amps.  I disconnected from the shore power and checked the battery voltage and all were above 2v.  I left the inverter on (charger off) for the day and all seems well.  The batteries only dropped by 5% which I think is fair.  I reconnected the mains to recharge the batteries and I am now again in Absorption but still reading around 25amps in.  Note that the battery levels were recently checked and adjusted but they were at overflow today.  I drew out around 300ml per battery to get the levels back down. Has anyone come across this problem? I cant figure whether it is the Charger or the batteries.  

Check every cell voltage, you may have one or more that is short circuit.

[dmr]

wot Tacy says, plus what was the total charging voltage when 25 amps were going into the batteries?  This will indicate if the charger is over-charging.

 

Taking electrolyte out of the batteries is not good, are you sure you did not over-fill them last time you topped them up?

Trouble with removing liquid is that you have taken acid out whilst you only top up with water so the acid is now slightly weaker. 300ml might be ok but don't do it again. Have you still got it? can you put it back in?

What is the total Ah capacity of your battery bank?

Are you sure that the Victron was not doing an equalise charge?

[nicknorman]

I’d check all the cells during charging. You need to measure to at least one decimal place - “over 2 volts” is too vague. They should all be the same within 0.1v or so. And check the overall charge voltage. As mentioned, if you do have to remove electrolyte then put it back in later, otherwise the acid strength will be wrong.

[steve.sharratt]

1 hour ago, Tracy D'arth said:

Check every cell voltage, you may have one or more that is short circuit.

I did check that when I disconnected the charger.  All were sitting at just above 2v. On charge they are all between 2.3 to 2.4.

43 minutes ago, dmr said:

wot Tacy says, plus what was the total charging voltage when 25 amps were going into the batteries?  This will indicate if the charger is over-charging.

 

Taking electrolyte out of the batteries is not good, are you sure you did not over-fill them last time you topped them up?

Trouble with removing liquid is that you have taken acid out whilst you only top up with water so the acid is now slightly weaker. 300ml might be ok but don't do it again. Have you still got it? can you put it back in?

What is the total Ah capacity of your battery bank?

Are you sure that the Victron was not doing an equalise charge?

Definitely didn’t overfill.  I use a battery bottle with the filler set to fixed level.  I assume as the acid heats it expands so I removed enough to drop the level but it is still above the normal level.  Kept the acid so it can go back in if necessary.  Batteries are 600ahr.

4 minutes ago, nicknorman said:

I’d check all the cells during charging. You need to measure to at least one decimal place - “over 2 volts” is too vague. They should all be the same within 0.1v or so. And check the overall charge voltage. As mentioned, if you do have to remove electrolyte then put it back in later, otherwise the acid strength will be wrong.

All batteries are within 0.05v.  I just checked the charging voltage and they are now at 2.3 to 2.4 and less than 0.1 variation.  They are getting old though it seems strange that they would all go at the same time.  Maybe not?

[cuthound]

Definitely sounds like one or more cells with a short circuit. 

 

Are any of the cells warm and do any have bowed ends to the casing? If either or both are present then the cell has avshort circuit and is at risk of exploding.

[Tony Brooks]

Or gassing yourself with sulphur dioxide (I think), anyway a nasty gas that a bit of exposure makes you go nose blind and then does nasty thing sot you. Any tarnished bright metal around the batteries?

[dmr]

2.4volt/cell (=14.4 on a 12 volt system) is not excessive, maybe even a little low.

A bit of bubbling/gassing is also ok, its a matter of degree.

25 amps is a bit high for the end of absorption phase (I assume this is where you where), thats 3% of your 800ah, but it might be just ok if the batteries are very old.

The smell is the concern, I assume the small was rotten eggs/H2S   ??????

Are any cells using much more or much less water than the others?

Have you got a hydrometer....if so can you test every cell and report back.

 

I would not worry if the electrolyte level is a bit high, as long as there is some air gap left/no danger of it getting out of the top.

[steve.sharratt]

30 minutes ago, cuthound said:

Definitely sounds like one or more cells with a short circuit. 

 

IAre any of the cells warm and do any have bowed ends to the casing? If either or both are present then the cell has avshort circuit and is at risk of exploding.

I 

The acid is warm but I think all of the casings are ok (but I will check again).  Wouldn’t a short show on a voltage check?

28 minutes ago, Tony Brooks said:

Or gassing yourself with sulphur dioxide (I think), anyway a nasty gas that a bit of exposure makes you go nose blind and then does nasty thing sot you. Any tarnished bright metal around the batteries?

That’s my main concern.  I have disconnected the charger for the night.

19 minutes ago, dmr said:

2.4volt/cell (=14.4 on a 12 volt system) is not excessive, maybe even a little low.

A bit of bubbling/gassing is also ok, its a matter of degree.

25 amps is a bit high for the end of absorption phase (I assume this is where you where), thats 3% of your 800ah, but it might be just ok if the batteries are very old.

The smell is the concern, I assume the small was rotten eggs/H2S   ??????

Are any cells using much more or much less water than the others?

Have you got a hydrometer....if so can you test every cell and report back.

 

I would not worry if the electrolyte level is a bit high, as long as there is some air gap left/no danger of it getting out of the top.

On first check all of the cell were starting to overflow which is why I dropped the levels. The cells are getting old so I am sure that isn’t helping.  It’s the smell that worries me too.  It’s the 25amps that I don’t get.  I did read that absorption can be affected if there is a big load on the batteries.  The load is less that 10 amps so I don’t think that would be the problem.

 

It is the dreaded rotten egg smell. I will be getting a hydrometer tomorrow.  The charger is off for the night so they have settled down now.  i will update when after the hydro test.

[cuthound]

8 minutes ago, steve.sharratt said:

Wouldn’t a short show on a voltage check?

 

Depends on the short. If it is caused by a build up of active material fallen from the plategrids, which has built up at the bottom of the battery, but hasn't yet reached the bottom of the plates, it can be a relatively high resistance short, which limits the current and doesn't depress the voltage or heat up the electrolyte much. "Trees" of foreign material between the plates causes similar shorts.

 

Buckled plates and/or when the active material reached the bottom of the plates can cause significant shorts which results in depressed voltage and higher currents which can heat the electrolyte up quite rapidly.

[MtB]

29 minutes ago, steve.sharratt said:

It’s the 25amps that I don’t get.

 

How do you know its 25 Amps?

 

Is it possible whatever instrument you're using is mis-reporting? Do you have a clamp meter to take an alternative measurement? 

[steve.sharratt]

1 hour ago, MtB said:

 

How do you know its 25 Amps?

 

Is it possible whatever instrument you're using is mis-reporting? Do you have a clamp meter to take an alternative measurement? 

Fair point.  Reading off the Victron Smartmeter.

[blackrose]

These are flooded lead/acid batteries?

 

Just to check, what battery type is Victron set to or does it have some method of sensing the battery type?

 

Edited October 1, 2023 by blackrose

[steve.sharratt]

It is set to LA.  The system was installed some years ago and I haven’t touched it.  I am currently trying to get into the VictronConnect app.

[steve.sharratt]

21 hours ago, dmr said:

2.4volt/cell (=14.4 on a 12 volt system) is not excessive, maybe even a little low.

A bit of bubbling/gassing is also ok, its a matter of degree.

25 amps is a bit high for the end of absorption phase (I assume this is where you where), thats 3% of your 800ah, but it might be just ok if the batteries are very old.

The smell is the concern, I assume the small was rotten eggs/H2S   ??????

Are any cells using much more or much less water than the others?

Have you got a hydrometer....if so can you test every cell and report back.

 

I would not worry if the electrolyte level is a bit high, as long as there is some air gap left/no danger of it getting out of the top.

I jut did the hydrometer test with the batteries at 90%.  All readings were at 1225 with one at 1200.  This seems to be correct but I will check again tomorrow when I get them back to 100%

[ditchcrawler]

46 minutes ago, steve.sharratt said:

I jut did the hydrometer test with the batteries at 90%.  All readings were at 1225 with one at 1200.  This seems to be correct but I will check again tomorrow when I get them back to 100%

1225 to 1200 is quite a difference in charge, that could be your problem

[dmr]

That low cell could be the problem, even though the difference is not huge.

According to the Trojan data sheet:

1.225 = 72% charge (approx)

1.220 = 62%

90% would be just under 1.260

Charge them more, assuming you can do this safely, and see if the low cell comes up.

Maybe get a fan going if you can do disperse any gasses.

Do you ever do an equalise charge?

I have seen a couple of failures on the Trojans where one cell just sits at a fixed SG regardless of any charge or disharge, never really understood this but Cuthounds high resistance short sounds like a possible explanation.

 

[ditchcrawler]

38 minutes ago, dmr said:

That low cell could be the problem, even though the difference is not huge.

According to the Trojan data sheet:

1.225 = 72% charge (approx)

1.220 = 62%

90% would be just under 1.260

Charge them more, assuming you can do this safely, and see if the low cell comes up.

Maybe get a fan going if you can do disperse any gasses.

Do you ever do an equalise charge?

I have seen a couple of failures on the Trojans where one cell just sits at a fixed SG regardless of any charge or disharge, never really understood this but Cuthounds high resistance short sounds like a possible explanation.

 

But he said its down to 1200 less than 1220 just over 50%

[nicknorman]

Seems that the 1200 cell is definitely knackered and pulling lots of current through the other cells.

[Tony Brooks]

It so happens that Lucas said a difference between cell relative density readings of 0.025 indicates a faulty cell. A difference of 0.030 was arguably better accepted, but it certainly looks like a duff cell.

[Onewheeler]

On 01/10/2023 at 19:37, Tony Brooks said:

Or gassing yourself with sulphur dioxide (I think), anyway a nasty gas that a bit of exposure makes you go nose blind and then does nasty thing sot you. Any tarnished bright metal around the batteries?

Hydrogen sulphide. Rotten eggs or fart smell. You can only smell it in low concentrations, which makes it dangerous.

[dmr]

1 hour ago, ditchcrawler said:

But he said its down to 1200 less than 1220 just over 50%

sorry,typo, bad fingers and rushing, 1200, but I still reckon this is 62%....or maybe 63 😀

[nicknorman]

20 minutes ago, dmr said:

sorry,typo, bad fingers and rushing, 1200, but I still reckon this is 62%....or maybe 63 😀

Even so, if all the other cells are fully charged and one is at 63%, that cell is duff.

[dmr]

2 minutes ago, nicknorman said:

Even so, if all the other cells are fully charged and one is at 63%, that cell is duff.

 

Yes, if the cells were all over the place then an equalisation might just do the job, but with just one low cell plus the smell it is looking bad.

Surprised this didn't show up when the op measred voltages, but the "cell stuck but not fully shorted" failure does some odd things.

 

800Ah of tractions at 24 volt is going to be a significant investment but replacing just the bad cell is probably not the way to go on old batteries.

Lithium ?????? 😀

[ditchcrawler]

It may be possible to get it refurbished, we did the fork lifts when they went down, just a single cell if the others are still OK