Happy 15th Birthday to my LiFePo4 Bank

[SaylorMade]

Originally Posted by wholybee

You won't damage them. What will happen is that as they get further out of balance there will reach a point that one cell has an over voltage event and the BMS disconnects. There won't be damage to the cell (because the BMS protected from that) but while disconnected you will be unable to charge further, and thus won't be able to balance further. You will have to go through a long and time consuming process to balance the battery before you can use it again.

23mV is ok, but not great. Probably all you need to do is set the absorption voltage to 14.1V and use the battery as normal. After a month or so of getting to that voltage every day, it'll probably get a little better.

Yes, that is also my understanding.

[CaptainRivet]

Originally Posted by wholybee

You won't damage them. What will happen is that as they get further out of balance there will reach a point that one cell has an over voltage event and the BMS disconnects. There won't be damage to the cell (because the BMS protected from that) but while disconnected you will be unable to charge further, and thus won't be able to balance further. You will have to go through a long and time consuming process to balance the battery before you can use it again.

23mV is ok, but not great. Probably all you need to do is set the absorption voltage to 14.1V and use the battery as normal. After a month or so of getting to that voltage every day, it'll probably get a little better.

That’s wrong, sorry. If you have imbalances from 150mV and higher there is a reason for that which eg means this one cell has a higher resistance which means that cell will get stressed even more as it always need to deliver more means it wears more=devil cycle. Deviations like this will continue to rise quickly if on that level already so battery will the soon be soon unusable=> if you have DIY or battery with direct access to cells like SOK marine buy an 5A active balancer, that will compensate this deviation and use 14,4V as absorption voltage. If you have sealed drop ins use 14,6 or if possible 14,8V as absorption to give the passive balancer as long time as possible…and make a warranty claim, if outside of warranty all you can do is keep it at 14,8V and if it’s getting unusable cut it open and add an active balancer.

Can be one reason, another reason is the battery never got a good top balance because people like him who has not much knowledge about this chemistry read here charge to 13,8V and your battery will live 15 years…
What Rod didn‘t say with a perfect top balance and that are Winston cells which are always delivered as perfectly matched cells so a proper top balance is possible and the cells can keep this top balance…not all cells and battery can do this.

So first steps: so you need this battery to be top balanced to figure out if it’s only a top balance issue or you got a bad quality battery with unmatched cells.

You have epoch batteries so use the epoch app and nothing else.
If that app has „balance only while charging“ enable that, or if you can disable balancing while discharging do that as this is most likely the origin of your problem. A passive balancer only works properly during charging and must be off during discharging. If non of this 2 options exist write epoch and ask how it should be configured.
If you have 23mV at 14,3V you will have >40mV at 14,6V means no top balance done.
2nd charge this battery to 14,6V which epoch defines as max voltage, so absorption of solar to 14.55V with 3h duration and float at 13,5V.
It can be the bms cut off with 14,55V then go step by step 0.05V down with absorption till BMS doesn’t cut off. If it’s eg 14,5V kept it there for the next month or longer till you have <15mV deviation, then rise the absorption voltage to 14,6V with 3h and keep it for the next weeks till also deviation reached <15mV. This means deviation value directly after! Cut off and NOT after hours when battery reaches its rest voltage which is 3,3-3.4V per cell and here you cannot see any deviation here. the deviation is NOT reducing which 5mV value shown fools you to believe. Deviation is only correct/visual above 13,8V or 3,45V and the higher to 14,8 or 3,65V you go the more precise deviation shown is. And the higher you initially charge for top balancing was and keep the voltage there, the better your top balance is.
After both batteries reached <15mV directly after cut off at 14,6V, reduce absorption to 14,2V and 30min per 100AH absorption duration time.
Now run these batteries for a month. After one month rise absorption to 14,6V again and check deviation directly at cut off, if
A) deviation is bigger then 15mV your cells are not properly matched and need a higher absorption voltage so the balancer can compensate this => keep 14,6V for 2 weeks minimum till deviation is back to <15mV at 14,6V cut off (bring battery back to top balance) and then reduce to 14,4V absorption as your permanent value. After a month at 14,4V check again with 14,6V when it cuts off, is deviation > 15mV keep your the absorption at 14,4V but all 2 month rise absorption for 2 weeks to 14,6V to top balancer your battery…you got unmatched cells.
B) if deviation is smaller then 15mV, congrats you got a good battery with matched cells. You can try to lower absorption to 14.0V or even 13,8V and check after a month with absorption set to 14,6V. If deviation rises above 15mV go to 14,2V as your permanent absorption voltage, if not 14V or 13,8V is ok.
Check after 6month with 14,6V if deviation rises, if yes just keep at 13,8 or 14V and all 6 month keep absorption at 14,6V for a week to do a top balance.

You can do this procedure with one charge source, solar or shorepower which is more convenient and leave the other charge sources as is. After you find your absorption value adjust all charge sources to that.

[chris in SG]

Taking a 'different tack' but consistent with the thread heading, my Victron LiFePo4 batteries (2 x 200Ah plus Victron BMS) are dying after 7 years hard use. By "hard use" I mean daily cycling to approx. 50% depth, on average.

According the attached Victron spec., 50% depth of discharge should deliver 5,000 cycles or approx. 14 years service. My 7 year lifespan corresponds to Victron's prediction for 80% daily discharge.

My overnight discharge is roughly 100Ah which was comfortable for a 400Ah storage. However, during overcast weather, I would allow the state of charge to drop to warning level (12v) before running the engine, thinking that I was allowed to enjoy release from the lead acid "never below 50%" rule.

For the last 3 years, battery capacity has gradually reduced so I have adjusted my battery monitor, by trial and error, from 400 Ah to 200Ah total. Obviously my %age discharge has therefore increased to more than 50% currently.

My questions for the experts:

• I'm confident that Victron does not exaggerate its performance, so what is the likely reason my batteries have aged so badly?
• If it is normal for capacity to reduce gradually, then why is this not discussed (never seen it discussed here)?
• I have ordered new batteries (same type) but it will take months to receive, due to dangerous goods restrictions. What is the risk of capacity going from 'much reduced' to 'off a cliff' and leaving me in the lurch?

I should add that my existing Victron batteries were not "smart", meaning there is no bluetooth access to their internal performance.

Please be gentle with your criticism..

[SaylorMade]

Originally Posted by chris in SG

My questions for the experts:

• I'm confident that Victron does not exaggerate its performance, so what is the likely reason my batteries have aged so badly?
• If it is normal for capacity to reduce gradually, then why is this not discussed (never seen it discussed here)?
• I have ordered new batteries (same type) but it will take months to receive, due to dangerous goods restrictions. What is the risk of capacity going from 'much reduced' to 'off a cliff' and leaving me in the lurch?

Not an expert, but who is?
Temperature is a big degradation factor for LithiumX batteries.
Are you in a hot climate, and is the area where they are stored very hot?
Your degradation is surely more than one should expect from LFP batteries.

[s/v Jedi]

Originally Posted by chris in SG

Taking a 'different tack' but consistent with the thread heading, my Victron LiFePo4 batteries (2 x 200Ah plus Victron BMS) are dying after 7 years hard use. By "hard use" I mean daily cycling to approx. 50% depth, on average.

According the attached Victron spec., 50% depth of discharge should deliver 5,000 cycles or approx. 14 years service. My 7 year lifespan corresponds to Victron's prediction for 80% daily discharge.

My overnight discharge is roughly 100Ah which was comfortable for a 400Ah storage. However, during overcast weather, I would allow the state of charge to drop to warning level (12v) before running the engine, thinking that I was allowed to enjoy release from the lead acid "never below 50%" rule.

For the last 3 years, battery capacity has gradually reduced so I have adjusted my battery monitor, by trial and error, from 400 Ah to 200Ah total. Obviously my %age discharge has therefore increased to more than 50% currently.

My questions for the experts:

• I'm confident that Victron does not exaggerate its performance, so what is the likely reason my batteries have aged so badly?
• If it is normal for capacity to reduce gradually, then why is this not discussed (never seen it discussed here)?
• I have ordered new batteries (same type) but it will take months to receive, due to dangerous goods restrictions. What is the risk of capacity going from 'much reduced' to 'off a cliff' and leaving me in the lurch?

I should add that my existing Victron batteries were not "smart", meaning there is no bluetooth access to their internal performance.

Please be gentle with your criticism..

Your first point of action is to question if the batteries have been fully charged for these 7 years. This can be tested by charging them to a higher voltage, let’s say 3.65V per cell so 14.6V for a 12V battery. This may trigger a HVC in one or both batteries but that’s okay. When charged to that level, do a couple deep cycles, bringing them back to that 14.6V every time. This may regain part of the lost capacity.

Next step would be to isolate the batteries and test each one separately. Maybe there’s a problem with one of them and the other is okay.

[CaptainRivet]

Originally Posted by chris in SG

Taking a 'different tack' but consistent with the thread heading, my Victron LiFePo4 batteries (2 x 200Ah plus Victron BMS) are dying after 7 years hard use. By "hard use" I mean daily cycling to approx. 50% depth, on average.

According the attached Victron spec., 50% depth of discharge should deliver 5,000 cycles or approx. 14 years service. My 7 year lifespan corresponds to Victron's prediction for 80% daily discharge.

My overnight discharge is roughly 100Ah which was comfortable for a 400Ah storage. However, during overcast weather, I would allow the state of charge to drop to warning level (12v) before running the engine, thinking that I was allowed to enjoy release from the lead acid "never below 50%" rule.

For the last 3 years, battery capacity has gradually reduced so I have adjusted my battery monitor, by trial and error, from 400 Ah to 200Ah total. Obviously my %age discharge has therefore increased to more than 50% currently.

My questions for the experts:

• I'm confident that Victron does not exaggerate its performance, so what is the likely reason my batteries have aged so badly?
• If it is normal for capacity to reduce gradually, then why is this not discussed (never seen it discussed here)?
• I have ordered new batteries (same type) but it will take months to receive, due to dangerous goods restrictions. What is the risk of capacity going from 'much reduced' to 'off a cliff' and leaving me in the lurch?

I should add that my existing Victron batteries were not "smart", meaning there is no bluetooth access to their internal performance.

Please be gentle with your criticism..

What you posted is the new smart with CaLb cells inside.
Your old victron batteries have winston cells inside, so top notch and better parameters means more cycles then Calb.
Definitely not normal they die after 7 years. DoD 50% and sometime a bit deeper is permium for winstons, you should get max cycles from them.

You are sure your capacity died and not that the battery is completely out of balance?
If you put your MPPT or shorecharger to 14.6V absorption at what voltage cuts the BMS effectivly the charge?
As Jedi said first charge both together and see waht happens, you actually want to have a cutoff by BMS as only this shows you where the battery really is. Then each seperatly. Please post this results and we help...I expect you have a huge devation and both are massivly out of balance.

You have a victron BMS so you should be able to see cell voltages and deviation. Which victron BMS do you actually have? Means how much balance current does it have?
Depending on that and your results with cutoff voltage we will help.

What were your charging parameters? Victrons default 14.4V with how long absorption time and 13.8V float?
Are the batteries in the engine room?

[Statistical]

Originally Posted by chris in SG

My overnight discharge is roughly 100Ah which was comfortable for a 400Ah storage. However, during overcast weather, I would allow the state of charge to drop to warning level (12v) before running the engine, thinking that I was allowed to enjoy release from the lead acid "never below 50%" rule.

I think you overdid that a bit. 12.0V is <10% SoC. That is pretty tough on LFP. I treat anything below 20% SoC as "emergency use only". If I can avoid it I will but in an emergency I will run it down to 0% SoC.

If it is normal for capacity to reduce gradually, then why is this not discussed (never seen it discussed here)?

It is normal and expected although I do wonder if your 50% measured drop in capacity is correct. Usually batteries will fail completely long before that. Battery life is general considered a drop in usable capacity of 20% (sometimes 30%).

I would recommend top charging the batteries and then use a consistent load to determine Ah. My guess is you get more than 200Ah out of 400Ah pack before LVDC.

Not sure if there is any way to measure the individual cell voltages on those batteries. I would be really curious to measure each cell voltage after charging the pack to 100% SoC, disconnecting all loads and charging sources and letting it stand for an hour. I do wonder if you just have a dud cell dragging the rest of the pack down.

[CaptainRivet]

Originally Posted by Statistical

I think you overdid that a bit. 12.0V is <10% SoC. That is pretty tough on LFP. I treat anything below 20% SoC as "emergency use only". If I can avoid it I will but in an emergency I will run it down to 0% SoC.



It is normal and expected although I do wonder if your 50% measured drop in capacity is correct. Usually batteries will fail completely long before that. Battery life is general considered a drop in usable capacity of 20% (sometimes 30%).

I would recommend top charging the batteries and then use a consistent load to determine Ah. My guess is you get more than 200Ah out of 400Ah pack before LVDC.

Not sure if there is any way to measure the individual cell voltages on those batteries. I would be really curious to measure each cell voltage after charging the pack to 100% SoC, disconnecting all loads and charging sources and letting it stand for an hour. I do wonder if you just have a dud cell dragging the rest of the pack down.

Its definitely not normal on winston based battery.

First question is battery completly out of balance or did the cells degrade. 2nd question what were his charge parameters...eg. if 13.8 float they were floated to death and engine room so capacity degrgation most likely and not much to rescue.

For that he need to charge to 14.6V and tell us the cutoff voltage or better the cell deviation at cut off.
Then we know if degrated cutoff at 14.4 or 14.6V or out of balance when cutoff at 14V or alike.

As soon as we get this info back we can then tell him what options he has. Tell him that now is speculation and can lead to even more damage.

[chris in SG]

Thank you all for the valuable advice. I will do the research suggested and get back to you. In the meantime,

- batteries are under a bunk at probably 28-30degC steady.

- BMS is the one shown attached, but the earlier non-smart version. I recall the local Victron agent (not in the Philippines) using his laptop to check the installation but this was definitely an 'admin only' access to the internals. I think he had a dongle to link into the 'daisy-chain'.

No need to respond to this, I'm just appreciating the shared knowledge, which obviously I should have requested much earlier..

[Maine Sail]

Originally Posted by rslifkin

From what I remember, the Epoch batteries activate the passive balancer starting at something like 13.4V when charging. I'd expect that if you hold them around 14 - 14.2V for a while the imbalance should start getting smaller.

Epoch starts balancing at 13.4V if there is a 30mV v-diff..

[Maine Sail]

My overnight discharge is roughly 100Ah which was comfortable for a 400Ah storage. However, during overcast weather, I would allow the state of charge to drop to warning level (12v) before running the engine, thinking that I was allowed to enjoy release from the lead acid "never below 50%" rule.

12V is below 50% in lead acid and close to 0% on LFP...

[TPG]

That is impressive, and thank you for sharing. Also thanks for the positive contributions you've made over the years, I've learned a great deal from your site and it encouraged me to learn more about power systems.

Best regards to you and your future endeavors!

[CaptainRivet]

Originally Posted by Maine Sail

Epoch starts balancing at 13.4V if there is a 30mV v-diff..

Wow that’s bad, means >100mV deviation at 3,65V when they start balance and then a tiny passive balancer should sort that quite big imbalance. On a 300AH battery 100mV at 3,65V is about 1AH difference means it takes weeks till that’s in balance.
Heard a lot good about epoch but that’s a noGo…they should have taken Jk BMS instead jbd one…2A active balancer balanced down to 5mV deviation.

[CaptainRivet]

Originally Posted by chris in SG

Thank you all for the valuable advice. I will do the research suggested and get back to you. In the meantime,

- batteries are under a bunk at probably 28-30degC steady.

- BMS is the one shown attached, but the earlier non-smart version. I recall the local Victron agent (not in the Philippines) using his laptop to check the installation but this was definitely an 'admin only' access to the internals. I think he had a dongle to link into the 'daisy-chain'.

No need to respond to this, I'm just appreciating the shared knowledge, which obviously I should have requested much earlier..

You should be able to troubleshoot the system yourself and have that adapter and pc program so you can check and adapt your system when needed.
Question is what do you wanna do with old battery and BMS, keep it and add the new then it makes sense and find out which adapter and computer Programm you need and buy it. Could be the mk2 adapter. So you can make adaptions or from time to time at least have a closer look at cell values and deviation. Makes troubleshooting much easier.

I am not a Victron crack but eg Jedi is and can maybe tell you what you need. I assume it’s a combo of Degradation and imbalance, the imbalance can be fixed the degration not anymore.
What are your charge parameters in MPPT (and other charge sources?), especially float. If at 13.8V reduce immediately to 13.5V so you don‘t keep them at too high voltage level. If that’s the case that would also explain the high Degradation, as location is sufficiently low temp that cannot be the issue here. There are mainly 2 factors to degragate a lifepo4 quickly and that heat or keeping it for long time on a high voltage level which is happening when you float it to death keeping it at a high voltage level…cycling it not really an issue with lifepo4 at a vessel as mostly DOD 50% max in average and occasionally deeper.

[jcapo]

Originally Posted by CaptainRivet

Wow that’s bad, means >100mV deviation at 3,65V when they start balance and then a tiny passive balancer should sort that quite big imbalance. On a 300AH battery 100mV at 3,65V is about 1AH difference means it takes weeks till that’s in balance.
Heard a lot good about epoch but that’s a noGo…they should have taken Jk BMS instead jbd one…2A active balancer balanced down to 5mV deviation.

There are two Epoch 300AH versions. My 300AH Epoch "Essentials" batteries were configured to start balancing at 13.6 with a 10mv deviation.

I changed the deviation to 5mv and then to 2mv to watch the balancer work.