failed EVE LF280 after 150 cycle!

[Amitis]

We purchased 100 cells of EVE and test all of them for capacity! All are above 280Ah , good shape and no major scratch, all relatively new and their production date in first quarter of 2023 ! their named A- grad! ( cells not directly bought from factory or kept more than 3 month without company testing results catagorized in A- ) we first top balanced cell in 3.65V and kept them parallel for a while! but after assembling them in battery packs and used them in low speed traction application just after about 150 working cycles dramatically cells capacity and voltage differ from each other!
one of the cells in 4S pack reach to 3.65 V during charging while other 3 cells are only 3.35V, from capacity point of view three cells have 75% capacity after charging is interrupted by bms because of over voltage of the first cell! while one cells reach its 100% we test again all cells individually all of them still have capacity above 280Ah !

but cells suffer from different internal discharge rate I think! although their internal resistance seems to be close to each other atleast with method of measurement by a multimeter equipped with internal resistance measuring function!

so it no matter how much a cell can keep its initial capacity after cycling but cells unbalancing after cycling is the most problem of the lithium battery issues ! even they're working for multiple thousand of cycle but after a hundred cycles the capacity of the battery packs limited to the lowest battery cell soc!
anyone here has same experience, what do you recommend?

 

[timselectric]

Active balancing

 

[timselectric]

If you haven't balanced for 150 cycles, that's the problem.

 

[LakeHouse]

test again all cells individually all of them still have capacity above 280Ah

There's nothing wrong with your cells, and they haven't 'failed'.
Your battery is out of balance and that can make it behave as though it has reduced capacity. Balance the cells and you'll get full capacity back.
Install an active balancer that only balances above 3.42V, and you'll likely keep the cells in balance, and maintain full capacity in the future.

 

[Steve_S]

We purchased 100 cells of EVE and test all of them for capacity! All are above 280Ah , good shape and no major scratch, all relatively new and their production date in first quarter of 2023 ! their named A- grad! ( cells not directly bought from factory or kept more than 3 month without company testing results catagorized in A- ) we first top balanced cell in 3.65V and kept them parallel for a while! but after assembling them in battery packs and used them in low speed traction application just after about 150 working cycles dramatically cells capacity and voltage differ from each other!
one of the cells in 4S pack reach to 3.65 V during charging while other 3 cells are only 3.35V, from capacity point of view three cells have 75% capacity after charging is interrupted by bms because of over voltage of the first cell! while one cells reach its 100% we test again all cells individually all of them still have capacity above 280Ah !

but cells suffer from different internal discharge rate I think! although their internal resistance seems to be close to each other atleast with method of measurement by a multimeter equipped with internal resistance measuring function!

so it no matter how much a cell can keep its initial capacity after cycling but cells unbalancing after cycling is the most problem of the lithium battery issues ! even they're working for multiple thousand of cycle but after a hundred cycles the capacity of the battery packs limited to the lowest battery cell soc!
anyone here has same experience, what do you recommend?

A few questions:
What configuration are these battery packs 4s, 8s,16s ?
What BMS are you using for these ? (provide link if possible)
You say "low speed traction", please define that as to what you are actually using them for and the conditions they have to operate within.

Next, provide information on your charging process.
How are you charging these ?
What is the equipment you are using ?
What is the charging profile settings exactly ?

There are several conditions & situations where this sort of thing can occur, to broad shot theories is of no help.
You are correct, that the weakest cell within a pack will be the limiter, this is true with all chemistries in fact. Sadly, this can extend to a battery bank with multiple packs.

 

[Amitis]

A few questions:
What configuration are these battery packs 4s, 8s,16s ?
What BMS are you using for these ? (provide link if possible)
You say "low speed traction", please define that as to what you are actually using them for and the conditions they have to operate within.

Next, provide information on your charging process.
How are you charging these ?
What is the equipment you are using ?
What is the charging profile settings exactly ?

There are several conditions & situations where this sort of thing can occur, to broad shot theories is of no help.
You are correct, that the weakest cell within a pack will be the limiter, this is true with all chemistries in fact. Sadly, this can extend to a battery bank with multiple packs.

1-What configuration are these battery packs 4s, 8s,16s ?

I've already mentioned in the previous post : 4S, but to be more detailed it is 3x4S packs in series ! 36V nominal ( 3×12.8= 38.4 V)

2-What BMS are you using for these ? (provide link if possible):

JBD 4S, 150A smart BMS , equipped with balancing function ( the only series of JBD that you can use BMS in series connection up to 4 packs ) here indeed we used 3 series of battery packs!

3-You say "low speed traction", please define that as to what you are actually using them for and the conditions they have to operate within.

floor washing machine everyday working charged and discharged battery once time in a day ! maximum drained current is about 70A from 280Ah cells and maximum of charge current is 30A

4- Next, provide information on your charging process.
We replaced customer charger with specific charger for lithium battery! So the charger , charge the battery packs up to 43.8V ( 3.65V/cells) then terminate charging process, infact if the battery cells well balanced ( just in first month that we top balanced the cells ) the current will decrease gradually in the end of charging process to below 3A and charger stopped ( but this second phases) only take a cuple of minutes and not too much time and most of the time of charging passed in constant current ( bulk mode)!

5-How are you charging these ?
as mentioned above ( in item 4 reply)

6-What is the equipment you are using ?
I'm afraid that don't catch what you mean of "what equipment" but if you mean what are these batteries using for? I said that they will be used for "electrical floor washing machine! "

7-What is the charging profile settings exactly ?
First constant current (CC) about 9hours !
second constant Voltage a few minutes!

please be noted that JBD BMS has balancing function 100 or 150mA but because I thought their algorithm for balancing aren't so useful we set the threshold voltage of cells in 3.48/cells ! at which cells are relatively full charge to prohibit from unwanted unbalancing because of BMS function but it seems that the cells really have problem of drifting and suffering from different discharge rate ! so that in 11 months and after about 150 cycle one of the battery pack drifted 25 % capacity with respect to other packs!

 

[timselectric]

You are also getting no balancing between 4s packs?
Your setup is definitely problematic. Having BMS controlled batteries in series. You need to add a battery balancer. Or manually separate and balance each battery weekly. (At your high cycle usage)

 

[OffGridForGood]

We replaced customer charger with specific charger for lithium battery!

Which one?
Make
Model
Settings?

So the charger , charge the battery packs up to 43.8V

Are you sure? maybe a typo here

 

[Partimewages]

If you're constantly charging the packs to 3.65 vdc per cell you probably have some high runners.
Charge to 3.45. Start the balance at 3.40.
As @timselectric said with 3 packs in series you will need a battery bank balancer also or your going to have to tear down the bank regularly.

 

[MisterSandals]

one of the cells in 4S pack reach to 3.65 V during charging while other 3 cells are only 3.35V,

If you can make each 4S battery have cells as similar as possible, each battery will function better.

If you can identify 4 runners that hit 3.65V early, put them together in one battery.
It is likely this battery will be better off alone as opposed to in series with 2 other batteries.

 

[OffGridForGood]

We purchased 100 cells of EVE and test all of them for capacity! All are above 280Ah

this is enough cells to build 25 4s packs, 280Ah each.

4S, but to be more detailed it is 3x4S packs in series ! 36V nominal ( 3×12.8= 38.4 V)

They built 4s packs, but then put them into series groups of 3 - why would anyone do this?
If you need 12s, just build 12s and the BMS can keep the cells properly balanced.
Three series packs of 4s will be very hard to keep balanced.

maximum drained current is about 70A from 280Ah cells and maximum of charge current is 30A

If you need 70Ah max, why use 280Ah cells?
A set of 100Ah cells would have been plenty.

The OP has tried to build a battery pack to run a floor machine, but they have missed the basics of how to design and build the battery to suit the machine. They already have the 280Ah cells, x 100 (is over $10,000 investment).
The best option is to start over, rebalance the cells, and build 12s battery packs with a BMS that can balance 12s, consider a BMS with 1-2A balance current, and revisit the charging profile.

 

[Amitis]

this is enough cells to build 25 4s packs, 280Ah each.



They built 4s packs, but then put them into series groups of 3 - why would anyone do this?
If you need 12s, just build 12s and the BMS can keep the cells properly balanced.
Three series packs of 4s will be very hard to keep balanced.



If you need 70Ah max, why use 280Ah cells?
A set of 100Ah cells would have been plenty.

The OP has tried to build a battery pack to run a floor machine, but they have missed the basics of how to design and build the battery to suit the machine. They already have the 280Ah cells, x 100 (is over $10,000 investment).
The best option is to start over, rebalance the cells, and build 12s battery packs with a BMS that can balance 12s, consider a BMS with 1-2A balance current, and revisit the charging profile.

yes 100 pcs is suitable for 25 packs of 4S it is sufficient for 8 devices (each required 3 packs) and 4 cells for reserve!

using 12S results to a single heavy battery bank weight! also we try to build replacement of Gel battery already they used with least change in mind of customers also try to find a way to use lithium battery as drop in type battery!

I didn't say "it is 70Ah" I said maximum discharge current is "70A"

 

[Amitis]

If you're constantly charging the packs to 3.65 vdc per cell you probably have some high runners.
Charge to 3.45. Start the balance at 3.40.
As @timselectric said with 3 packs in series you will need a battery bank balancer also or your going to have to tear down the bank regularly.

can you introduce me a battery bank balancer , can you share a link of such balancer model for 12V battery banks?

 

[OffGridForGood]

yes 100 pcs is suitable for 25 packs of 4S it is sufficient for 8 devices (each required 3 packs) and 4 cells for reserve!

using 12S results to a single heavy battery bank weight! also we try to build replacement of Gel battery already they used with least change in mind of customers also try to find a way to use lithium battery as drop in type battery!

I didn't say "it is 70Ah" I said maximum discharge current is "70A"

12s is heavy with 280Ah cells - very true! about 150lbs (68kg) Do the batteries need to be removed very often?
If you are stuck with 3x 4s then you need to either have careful matching of cells/IR and charging, or consider 3 Parallel packs =12v and add a DC to DC transformer to allow the machine to run on 36v.

 

[Amitis]

yes you are absolutely right!
After we experienced this issue we sort cells with relatively similar discharge rate in single packs but still in bulk production you can not garantee that similar bank to be used as series! and it realy might be possible that different battery banks to be series accidentally!
Anyhow I never thought that just after 150 cycles " 4000 cycle cells" need to be rebalanced! because we have experienced 105 Ah cells before in 24V single packs and after 5 years their cells still have good balance!

If you can make each 4S battery have cells as similar as possible, each battery will function better.

If you can identify 4 runners that hit 3.65V early, put them together in one battery.
It is likely this battery will be better off alone as opposed to in series with 2 other batteries.

 

[upnorthandpersonal]

Anyhow I never thought that just after 150 cycles " 4000 cycle cells" need to be rebalanced! because we have experienced 105 Ah cells before in 24V single packs and after 5 years their cells still have good balance!

Like someone said: if you have 12V batteries in series with separate BMS etc., you have to balance the batteries as well, not just the cells in each battery. A single 24V pack with a BMS will be a lot less troublesome in this regard. That's why I recommend if people want to go 48V: build a 48V battery, don't put 12V or 24V batteries in series, even if the BMS can handle this configuration.

 

[OffGridForGood]

Anyhow I never thought that just after 150 cycles " 4000 cycle cells" need to be rebalanced! because we have experienced 105 Ah cells before in 24V single packs and after 5 years their cells still have good balance!

And you prove the point with your own experience: 24v single packs remain in balance, but series connected separate packs will not. (at least not unless you take special steps to keep them in balance)

 

[MisterSandals]

we sort cells with relatively similar discharge rate

I've sorted a couple different ways and capacity testing (with 4 wire tester) had best immediate results.
Moving fliers (lower capacity) together and laggards (higher capacity) together works well too but its a process of many iterations.

Why did you settle on discharge rate? Thats new to me.

Agree with others, single 8S battery FAR easier than 4S3P.

 

[Amitis]

I've sorted a couple different ways and capacity testing (with 4 wire tester) had best immediate results.
Moving fliers (lower capacity) together and laggards (higher capacity) together works well too but its a process of many iterations.

Why did you settle on discharge rate? Thats new to me.

Agree with others, single 8S battery FAR easier than 4S3P.

I meant "self discharge rate" because 4 wire internal resistance measuring devices can't reflect real discharge rate and only show static internal resistance that can't so helpful because most of the cells have more or less similar resistance in our tests!

 

[Checkthisout]

Already posted but putting in my 3rd or 4th vote just make a single 36 volt pack with a single BMS. ?

We have a Tennant walk-behind. I hate that it's 36 volts.

"At Tennant, we use this one weird voltage so we can guarantee absolutely no readily available chargers on the market will work on our stuff" ?