JBD 7s-21s BMS acting weird

[Suijkerbuijk]

I see what happens
The bms calculation is wrong .
I see that happens if a cell is not correct.
The total volts is correct but your ampère are not.
So the bms think its that .

Same problem here

So it means new top balance the cells again for you go parallel again.
Or switch one bms its charger off.
So only one Battery is charge

No battery is the same so you always have some change .
But than again you use mix battery Ah and that ask that it go wrong .
The moment one battery hit the max volt the charge will stop and will not charge the other battery.
Soon or later that battery will go out of balance.

Reason in all Manuel it tell use the same battery in parallel with the same brand and same Ah.

 

[fnnwizard]

I see what happens
The bms calculation is wrong .
I see that happens if a cell is not correct.
The total volts is correct but your ampère are not.
So the bms think its that .

Same problem here

So it means new top balance the cells again for you go parallel again.
Or switch one bms its charger off.
So only one Battery is charge

No battery is the same so you always have some change .
But than again you use mix battery Ah and that ask that it go wrong .
The moment one battery hit the max volt the charge will stop and will not charge the other battery.
Soon or later that battery will go out of balance.

Reason in all Manuel it tell use the same battery in parallel with the same brand and same Ah.

By its very nature of being in P, will self balance out with other packs when potential gets far enough apart if build quality is at least somewhat same for both.

I think in manual, it is saying to use same cell within pack.

The moment a pack goes into protection mode and disconnects itself from inverter, the other pack keeps working unless it too goes into protection mode.


Anyhow, for OP:
Here’s a link for optimized bms settings relative to inverter settings.

F

Thread 'Tips on BMS Balancer Optimization and Various Discharge Curves for LF280K (V3)'

Nov 22, 2024

Reference green yellow red visual below.

Set BMS Cell Protection to 2.500V to 3.650V

Set BMS total pack Voltage limits. For me it is 44.0V – 58. Dependent on typical Load -->C rate

Inverter range for me: 48.0V to 56.4V

Balancing to start @ 3.410V with differential 20mV, off at 10mV, Can be adjusted once cells in consistent balance.

I run closed loop, but Voltage based, not SOC based. SOC is not accurate unless SOC is reset via batts 100% charged daily.

2 main reasons why SOC % is not accurate is that:
1: Most BMS shunts are only accurate to +-5%.
2: With small power draw from...

• fnnwizard

• 

 

[Suijkerbuijk]

By its very nature of being in P, will self balance out with other packs when potential gets far enough apart if build quality is at least somewhat same for both.

I think in manual, it is saying to use same cell within pack.

The moment a pack goes into protection mode and disconnects itself from inverter, the other pack keeps working unless it too goes into protection mode.


Anyhow, for OP:
Here’s a link for optimized bms settings relative to inverter settings.

F

Thread 'Tips on BMS Balancer Optimization and Various Discharge Curves for LF280K (V3)'

Nov 22, 2024

Reference green yellow red visual below.

Set BMS Cell Protection to 2.500V to 3.650V

Set BMS total pack Voltage limits. For me it is 44.0V – 58. Dependent on typical Load -->C rate

Inverter range for me: 48.0V to 56.4V

Balancing to start @ 3.410V with differential 20mV, off at 10mV, Can be adjusted once cells in consistent balance.

I run closed loop, but Voltage based, not SOC based. SOC is not accurate unless SOC is reset via batts 100% charged daily.

2 main reasons why SOC % is not accurate is that:
1: Most BMS shunts are only accurate to +-5%.
2: With small power draw from...

• fnnwizard

• 

Not by Charging up .
By discharge you are correct
By Charging this happens.
If you set the charge max under 14.6 volts .
The bms will not shutdown it do not hit that 14.6 .
Even if the charge is switch off the discharge stay on and that push the volt up .
The moment the second battery have unbalanced sell and hit the same volts it stop charging

14 volts stay 14 volts that is the output from 4 cells
If one cell is low but other are higher that compensate still to that 14 volts .
So you can hit that volts of 14 with unbalanced cells.

The problem is here the lifepo4 battery have a long really long the same volts output.
Well the Ah can really be different.
Same with charging.
So the higher Ah battery wil not hit that max 3.65 volt cell.

That is what i think what happens with different ah battery.

 

[fnnwizard]

Not by Charging up .
By discharge you are correct
By Charging this happens.
If you set the charge max under 14.6 volts .
The bms will not shutdown it do not hit that 14.6 .
Even if the charge is switch off the discharge stay on and that push the volt up .
The moment the second battery have unbalanced sell and hit the same volts it stop charging

14 volts stay 14 volts that is the output from 4 cells
If one cell is low but other are higher that compensate still to that 14 volts .
So you can hit that volts of 14 with unbalanced cells.

The problem is here the lifepo4 battery have a long really long the same volts output.
Well the Ah can really be different.
Same with charging.
So the higher Ah battery wil not hit that max 3.65 volt cell.

That is what i think what happens with different ah battery.

Sure, what you describe can happen to any pack regardless of cell size. That’s why it’s very important to keep V the same for each cell within the pack, The size of cells alone doesn’t affect balancing between packs tho.

As soon as the offline pack goes online again, they will each try to balance each other out, as long as each cell is reasonably within balance.

During higher Crate charge and discharge, current could be different for each pack. But under lower Crates, they will try to self balance.


Also, how the packs are parallel wired does matter … but only if it’s always running at high C-rates.

 

[ericfx1984]

Your single full Voltage setting at 3.45V hints to me that your OVP is prob set too low. Likely at 3.45 V?
That’s where it looks like charging was stopped at.
What does “overvoltage” read at the very top of that “parameter view” page?

No... It's not. OVP is set at 3.65 volts per cell

 

[fnnwizard]

No... It's not. OVP is set at 3.65 volts per cell

Can u tap on the double clock and post history? That will give hi and low cell V info.

At that charge rate, the high cell could very likely have hit 3.65+V but may not have been captured in the chart.
It stayed at an elevated level for quite some time before dropping enough to kick charge back on at almost dame level it kicked it off.

 

[ericfx1984]

Can u tap on the double clock and post history? That will give hi and low cell V info.

At that charge rate, the high cell could very likely have hit 3.65+V but may not have been captured in the chart.
It stayed at an elevated level for quite some time before dropping enough to kick charge back on at almost dame level it kicked it off.

I'll look at that a little later on... I'm actually planning to do a high rate charge where I sit there and monitor it manually

Is there a way to increase the resolution of the chart? And maybe speed up the capture rate?

I suppose I could also also increase the reconnect voltage... I believe I haven't set to 3.55 right now... But that's a thing... It's at 3.533... It doesn't record anything above that and even if it did hit over voltage protection on cell 3 or any cell for that matter, all of the cells have dropped below the threshold of 3.55 which should have triggered a reconnect but I don't see any actual disconnect happening...

 

[fnnwizard]

I'll look at that a little later on... I'm actually planning to do a high rate charge where I sit there and monitor it manually

Is there a way to increase the resolution of the chart? And maybe speed up the capture rate?

I suppose I could also also increase the reconnect voltage... I believe I haven't set to 3.55 right now... But that's a thing... It's at 3.533... It doesn't record anything above that and even if it did hit over voltage protection on cell 3 or any cell for that matter, all of the cells have dropped below the threshold of 3.55 which should have triggered a reconnect but I don't see any actual disconnect happening...

You can zoom in on the graph (two finger zoom on mobile) and it will display actual units. I'm not sure if u can set capture rate on your device, I only have older JBD devices (2019 and older).

If u can post parameters, we can see if there is anything amiss.

 

[ericfx1984]

You can zoom in on the graph (two finger zoom on mobile) and it will display actual units. I'm not sure if u can set capture rate on your device, I only have older JBD devices (2019 and older).

If u can post parameters, we can see if there is anything amiss.

So even with a really close zoom in we can still see that it never reached 3.65 volts... And as such should not have triggered OVP


As I'm looking through the logs I can't find anything That would suggest there was ever a battery cell over voltage...

 

[ericfx1984]

Besides that OVP does not stop discharge only charge... At least that's always been my understanding

I mean if it does stop discharge that would create more of a problem than anything

 

[Quattrohead]

So if you disconnect the "working" battery and only use this "deficient" battery does it then work on its own ok?

 

[Suijkerbuijk]

(Battery packs in parallel) (Not supported)
Link to the manual for your entertainment.

Yes it do see the part i have select in that maneul.

But one warning its that max charge.
Is the same for singel or parallel setup.

 

[justgary]

Besides that OVP does not stop discharge only charge... At least that's always been my understanding

I mean if it does stop discharge that would create more of a problem than anything

My JBD BMSs also do this, and it is driving me crazy. I replaced the one that I thought might have a weak contactor, but the problem simply moved to the other BMS.

It looks to me like the idle timeout decides that it can open the contactor but never closes it again since the other battery easily handles the load. I would like to be able to completely disable the idle timeout.

I have recently sent an email to Jaibaida to see if they can help, but they have not replied yet.

 

[fnnwizard]

Besides that OVP does not stop discharge only charge... At least that's always been my understanding

I mean if it does stop discharge that would create more of a problem than anything

I thought I read in the manual for that model, it would disconnect for both.
But should be easy to verify. Just do a charge to ovp and see what happens to the red circled display.

Also, can you try to zoom in on data when the charge current was 60+A?

My JBD BMSs also do this, and it is driving me crazy. I replaced the one that I thought might have a weak contactor, but the problem simply moved to the other BMS.

It looks to me like the idle timeout decides that it can open the contactor but never closes it again since the other battery easily handles the load. I would like to be able to completely disable the idle timeout.

I have recently sent an email to Jaibaida to see if they can help, but they have not replied yet.

Yes, the idea is to never have the BMS disconnect unless truely in a state of OVP,UVP.
The inverter V settings would help with that if set to be inside BMS working limits.

 

[ericfx1984]

I thought I read in the manual for that model, it would disconnect for both.
But should be easy to verify. Just do a charge to ovp and see what happens to the red circled display.

Also, can you try to zoom in on data when the charge current was 60+A?



Yes, the idea is to never have the BMS disconnect unless truely in a state of OVP,UVP.
The inverter V settings would help with that if set to be inside BMS working limits.

The voltage on the chart that you circled has not met the OVP threshold nor is it still above the OVP reconnect threshold... Meaning it is below OVP therefore OVP would not have triggered... But even if it had triggered, it is still below the threshold to reconnect meaning it should have reconnected

 

[fnnwizard]

The voltage on the chart that you circled has not met the OVP threshold nor is it still above the OVP reconnect threshold... Meaning it is below OVP therefore OVP would not have triggered... But even if it had triggered, it is still below the threshold to reconnect meaning it should have reconnected

Understood, I was trying to see at what V did the charger started to limit the current. Trying to rule out most obvious 1st, then work from there.

The contactor was still closed because current was still allowed to flow, albeit at a lower level from ~77A to less than 5A in that circled area.

Then it basically went from small charge to small discharge to high charge to standby.

What looks not right is that #3 high V cell also went below avg pack V during small discharge and during that standby.

Makes it look like either cell is bad or there is connection issue.

What charger are you using and what are its settings at?
Was this 2 packs hooked up or just one during the circled area =( ~77A x 2?), could the charger itself be in protection?

The moe info you can provide the quicker/easier we can help isolate and pinpoint to get to root cause and possibly find a fix.

 

[ericfx1984]

Understood, I was trying to see at what V did the charger started to limit the current. Trying to rule out most obvious 1st, then work from there.

Not certain

What looks not right is that #3 high V cell also went below avg pack V during small discharge and during that standby.

Makes it look like either cell is bad or there is connection issue.

Could be? I do notice that the voltages I get with my multi meter are slightly different, slightly lower than the BMS reports

Additionally I do have a spare 304 amp hour Eve cell that is brand new in the box

What charger are you using and what are its settings at?
Was this 2 packs hooked up or just one during the circled area =( ~77A x 2?), could the charger itself be in protection?

EG4 chargeverter set to 85 amps, I believe 55.2 volts... The current is shared between the pair of batteries

It's never a perfect split... Sometimes it'll be pretty darn close to a 50/50 split in current but other times it may be 40 60...

 

[justgary]

My BMS does not go into OVP, the contactor just drops and stays open. Either the contactor isn't getting enough current to stay closed or the BMS is intentionally doing it. I'm underpaneled and charging at about 54.4V, generally at under 18A. Ideally that is shared at around 9A per battery, but then one BMS drops out. The fact that one battery may take more current than the other when both are in the circuit just tells me that one battery has a lower SOC than the other and needs more current to charge.

This problem only happens when I am away, so I can't catch the conditions when it happens. When I get there I have to pull the connector from the BMS and reinsert it to get it to work again. At that point the contactor clicks and charge/discharge work. I have checked the app before I reset, and it shows that both the charge and discharge FETS are on, but the app does not show the status of the contactor. If it did, I would simply have my microcontroller tell it to close the contactor every five seconds.

The site is essentially a weekend cabin, so I don't need to rapidly recharge the batteries. They have at least five days to recharge before the next big use. I leave the inverter on so the sprinkler timer can water a few fruit trees (via the 240V well).

The inverter is a Magnum MagnaSine 4448PAE and the SCC is an Outback FlexMax 80. 3S2P 265W panels.

The issues as I see them:
- The JBD BMS will drop the contactor for no apparent reason. I presume it is an idle timeout on the battery with less charge.
- The JBD BMS has an idle timeout that cannot be disabled. 65,535 seconds is about 3/4 of one day.
- The JBD App does not show the status of the contactor.
- The JBD App does not allow one to control the contactor.

 

[Quattrohead]

You cannot parallel the JBD contactor BMS.

 

[sunshine_eggo]

You cannot parallel the JBD contactor BMS.

Except the manual contradicts itself.

 

[Quattrohead]

This thread and my personal experience says you cannot at the end of the day. Chinglish information contradicting itself, now there's a first.

 

[sunshine_eggo]

This thread and my personal experience says you cannot at the end of the day. Chinglish information contradicting itself, now there's a first.

Speaking of Chinglish, I have seen MANY BMS claim that they can't be paralleled, but I have always interpreted that as not paralleled on the same battery as there are folks who take that approach when trying to get higher current out of a single battery, and a single BMS is not sufficient.

 

[42OhmsPA]

This thread and my personal experience says you cannot at the end of the day.

How old are yours and did you ever update the firmware?
Mine span 2.5yrs and 2 vendors with whatever firmware they shipped with.
As I already stated, 0 issues with 4 in parallel.

Chinglish information contradicting itself, now there's a first.

Lol

 

[Quattrohead]

My two contactor BMS are slightly different, the older circular type contactor and the newer block type contactor. I also have four of the regular Overkill type JBD BMS.
So I had all of these paralleled and for a while they all performed equally and everything was great, then I started to notice one of the contactor BMS basically became lazy, it wouldn't give power until the others were way down in SOC. This might also coincided with the heat of the summer.
I double checked the settings which seem to be the same but nevertheless I cloned the settings from one contactor BMS into the other and still the same weird behavior continued. It got to the point where it just would never contribute anymore. Like you all I thought it was dead.
I pulled that battery out of the bank and tested it on its own and it works absolutely fine and indeed has been my test battery ever since. It's about to go into a golf cart.
I don't know what it is about them but JBD obviously know about it and have warned us about it and yet we still fight about it.
Someone here likes to way over analyze situations and has ended up confusing the whole situation. The bottom line is you cannot parallel JBD contactor BMS's reliably, they might or might not work for any amount of time, some amount of time or possibly no amount of time.

 

[Suijkerbuijk]

Speaking of Chinglish, I have seen MANY BMS claim that they can't be paralleled, but I have always interpreted that as not paralleled on the same battery as there are folks who take that approach when trying to get higher current out of a single battery, and a single BMS is not sufficient.

I think you hit the jackpot here.
Special with big Ah battery wel the bms are max out.