failed EVE LF280 after 150 cycle!

[Quattrohead]

Balancing only happens during charging not discharging so that is not a consideration. As others have said single battery bank controlled by single BMS charged by a single charger. K i s s

 

[740GLE]

Program the BMS to balance above a voltage not just during charging, that way if they float all night they’ll balance 8-12hrs.

 

[Ampster]

Either way the OP has some choices which are better than how the post started out with him thinking his investment in 100 cells has gone down the drain.

 

[Checkthisout]

OP, just crash a forklift into the machine going as fast as you possibly can so they have to buy a new model with lithium batteries already installed.

 

[Amitis]

REC BMS

I checked it but they have some Master/Slave BMS comunicate with each other by means of serial connection like CAN bus or RS485 and wifi only used for comunication between monitoring center and BMS! I'm looking for a Master/ Slave BMS that their "comunications between individual bms " will be based on wireless like Bluetooth or wifi!

 

[OffGridForGood]

I checked it but they have some Master/Slave BMS comunicate with each other by means of serial connection like CAN bus or RS485 and wifi only used for comunication between monitoring center and BMS! I'm looking for a Master/ Slave BMS that their "comunications between individual bms " will be based on wireless like Bluetooth or wifi!

can you make a wire harness for the balance wires, and use JTS connectors between the separate batteries, one BMS ?

 

[MisterSandals]

can you make a wire harness for the balance wires, and use JTS connectors between the separate batteries, one BMS ?

but to be more detailed it is 3x4S packs in series

When you connect batteries in series an individual cells between those batteries in parallel, you have a dead short. Fortunately with 22awg balance wires, it would be short lived and probably not a "shorts filling" experience.

 

[OffGridForGood]

All the cells are in series in a 12s pack. (they don't "know" if they are all in one group of 12 or three groups of 4)
His cells can be in series in three groups of four, connected with cables instead of bus bars between each group of 4.
The three groups get one 12s BMS, and to accommodate moving the groups of 4, some connectors for the BMS wires with JST connectors.

 

[OffGridForGood]

Still needs proper charge control - but we are getting closer to a simple solution...

 

[Marinepower]

2 of these?

Battery Balancer - Victron Energy

Equalize the state of charge of two series connected 12V batteries using the Battery Balancer. Find a Victron Energy dealer near you.

www.victronenergy.com

 

[Amitis]

Thanks for sharing good ideas to overcome this issue but we just rebalanced the cells and packs to see what happened in the future also we adjust the balancing to be started at lower voltage around 3.3V/cell instead of previous 3.48 V/ceIl (non-effective way) , Although we think that good grade cells shall not suffer from such unbalancing issues just after 150 cycles even if no balancing enabled! otherwise we should say that they didn't sell us A grade cells! because according to datasheets and standard conditions these cells can be charged up to 3.65V/cells and discharged to 2.5V/cells in 25 degree centigrade for more than 3500 cycles ! and we are not yet closed to 10 percent of such life cycle! if the voltage and consequently soc is so depending to balance issues then that should be main problem of this technology no matter how many times they can be cycled!

 

[upnorthandpersonal]

adjust balancing in lower voltage around 3.3V/cell instead of previous 3.48 V/ceIl

Won't help at all. You're well in the flat part of the LFP charge/discharge curve.

we think that good cells grade shall not suffer from such unbalancing issues just after 150 cycles even if no balancing enabled

Did you specify that these cells have to be capacity and IR matched over the entire charge/discharge cycle?

By the way, cars use balancers as well - there is a reason Tesla for example tells you to charge their LFP models to 100%: it's the only state of charge where they can perform the balancing.

 

[Amitis]

Won't help at all. You're well in the flat part of the LFP charge/discharge curve.



Did you specify that these cells have to be capacity and IR matched over the entire charge/discharge cycle?

By the way, cars use balancers as well - there is a reason Tesla for example tells you to charge their LFP models to 100%: it's the only state of charge where they can perform the balancing.

We're experienced that the issue isn't related to match capacity of the cells instead it is related to voltage drift of the cells and different self discharge during long time ! we couldn't check dynamic internal resistance measuring but we measured at first cells IR and all of them somehow are similar and just had 0.01 mili ohm difference! anyhow if Teala and others use active balancer it shows that this is a real problem of such technology although we had some other cells with longer term experience about 5 years and still have good balance without problem of balancing and their bms had not even have passive balancer!

 

[Checkthisout]

We're experienced that the issue isn't related to match capacity of the cells instead it is related to voltage drift of the cells and different self discharge during long time ! we couldn't check dynamic internal resistance measuring but we measured at first cells IR and all of them somehow are similar and just had 0.01 mili ohm difference! anyhow if Teala and others use active balancer it shows that this is a real problem of such technology although we had some other cells with longer term experience about 5 years and still have good balance without problem of balancing and their bms had not even have passive balancer!

Would still love to see pics of the install

 

[OffGridForGood]

Without balancing - it is just a matter of time and the cell voltages will eventually drift apart.
I bought active balancers for my packs, but none are installed, careful work with initial top balance, and settings for charging the cells; and passive balancing has worked to keep all my cells in balance.

 

[zanydroid]

To overcome the BMS issue, the OP would need a sphistacted system with wireless comms between the three cells, on master BMS and two slave BMS to follow instructions. Pretty tough to see how this would be cost effective.

How would the wireless BMS be able to balance the cells across battery packs? Passively dissipate the energy of the over voltage packs?

Is it not possible to invent a wiring harness for 12V packs that will carry across sensors and

 

[OffGridForGood]

why not use three sets of 4 cells, 12s BMS attached to pack 1.
Pack 1 has BMS cell leads to cells 1, 2, 3, 4.
Pack 1 has JST 4-pin connectors for leads 5,6,7,8 in one set, and 9,10,11,12 in another set.
Pack 2 has the mate JST 4-pin connector and short leads to the four cells in proper order (5,6,7,8)
Pack 3 ditto for cells 9,10,11,12.

In place, the packs are connected in series with standard battery cables.

The BMS doesn't know the difference between a bus bar and a large battery cable, assuming the packs are close together in a battery box.
This allows the packs to be shop prepped but user installed. Plug and play.


The OP still needs to address the LFP needs a proper charger suitable for LFP since these are replacing the L-A originals and the charge parameters are different.

 

[Zwy]

We're experienced that the issue isn't related to match capacity of the cells instead it is related to voltage drift of the cells and different self discharge during long time ! we couldn't check dynamic internal resistance measuring but we measured at first cells IR and all of them somehow are similar and just had 0.01 mili ohm difference! anyhow if Teala and others use active balancer it shows that this is a real problem of such technology although we had some other cells with longer term experience about 5 years and still have good balance without problem of balancing and their bms had not even have passive balancer!

It is about resistance of the circuits between the 12V packs causing imbalance with the packs in series. This is why a 36V pack is built with one BMS, all busbars between cells.

You could get away possibly by having all cables/busbars between cells and packs that are all equal length.

 

[Zwy]

why not use three sets of 4 cells, 12s BMS attached to pack 1.
Pack 1 has BMS cell leads to cells 1, 2, 3, 4.
Pack 1 has JST 4-pin connectors for leads 5,6,7,8 in one set, and 9,10,11,12 in another set.
Pack 2 has the mate JST 4-pin connector and short leads to the four cells in proper order (5,6,7,8)
Pack 3 ditto for cells 9,10,11,12.

In place, the packs are connected in series with standard battery cables.

The BMS doesn't know the difference between a bus bar and a large battery cable, assuming the packs are close together in a battery box.

The BMS won't know the difference but the packs under load will have different resistance in the cables, thus the problem of imbalance as a result.

Resistance across the whole circuit has to be the same.

This allows the packs to be shop prepped but user installed. Plug and play.


The OP still needs to address the LFP needs a proper charger suitable for LFP since these are replacing the L-A originals and the charge parameters are different.

 

[zanydroid]

The BMS won't know the difference but the packs under load will have different resistance in the cables, thus the problem of imbalance as a result.

Can you walk me through how the extra resistance between cells 4-5, 8-9 exacerbate the imbalance? Do the ones with extra resistance see a bigger load than the ones without?