JBD 7s-21s BMS acting weird

[ericfx1984]

So I have a pair of JBD 7S-21s 200a Smart BMSs

They're both set up at 16S, one of them has 280 amp hour eve cells the other one has 304 amp hour Eve cells

Got a full charge ... But I noticed this morning that the 304 amp hour one was sitting at 100% charge nothing doing in and nothing going out

But for some reason the 280 amp hour was sitting really low at like 60%

So I fired up the charger and noticed that nothing was going in or out on the 304 amp hour one

I disconnected the small balance plug and reconnected it to reset the BMS... It immediately started charging for a few minutes and then leveled out to almost no charge...

I'm really confused by this... Is this a sign BMS that is about to fail, or is it something else?

I guess what I'm saying is should I be buying another BMS just in case?

And if I should be buying a BMS, where do you suggest getting them from?

 

[sunshine_eggo]

Was there a disparity in the total voltage between the two batteries?

DId you verify all BMS reported values with separate instruments like a Voltmeter and DC ammeter?

 

[ericfx1984]

Was there a disparity in the total voltage between the two batteries?

DId you verify all BMS reported values with separate instruments like a Voltmeter and DC ammeter?

Well that's the thing... As I looked at the one that did seem to be working current was flowing to it... I had a little over 85 amps going to it as soon as I reset the BMS that did not seem to be working, the current split between them

There was a difference between them. But I think that's only because the 304 amp hour unit was not discharging... I've since recharged both of them and they are now balanced

 

[ericfx1984]

Well... It froze again

What I've noticed is each time that it has done this I've been charging the batteries using the EG4 chargeverter at night

In the morning I noticed that the battery that did not stop discharging / charging was down around 50% and the one that did stop charging / discharging It was still registering at 100% But was down around 53.9 volts

When I started the charge router up, all the power went to the battery that was at 50ish percent... But if I disconnect and reconnect the small balance cable on the battery that was not discharging / charging Then it would start charging, but only a very small charge before it came back up to 100%, while the majority of the charge current would go to the 50% battery

I suspect this BMS is going to fail. I think it's time to order another one and just leave this as a questionable backup

 

[sunshine_eggo]

Well... It froze again

What I've noticed is each time that it has done this I've been charging the batteries using the EG4 chargeverter at night

In the morning I noticed that the battery that did not stop discharging / charging was down around 50% and the one that did stop charging / discharging It was still registering at 100% But was down around 53.9 volts

When I started the charge router up, all the power went to the battery that was at 50ish percent... But if I disconnect and reconnect the small balance cable on the battery that was not discharging / charging Then it would start charging, but only a very small charge before it came back up to 100%, while the majority of the charge current would go to the 50% battery

I suspect this BMS is going to fail. I think it's time to order another one and just leave this as a questionable backup

Wow. That's really weird. You're probably right. Time to replace.

 

[ericfx1984]

Wow. That's really weird. You're probably right. Time to replace.

I suspect what is happening is that the contactor is freezing in the closed position for some reason... But it looks like for $125 I can have a new unit at my door so it's not really a huge concern

Once I get it out of the mix I can build a test bench using 18650 cells allowing me to charge the cells, albeit significantly lower rate of charge, and see if I can duplicate the failure

 

[Quattrohead]

Unfortunately this is why you cannot parallel the contactor JBD BMS. Unless all the cells and all of the wire resistances and everything else is all exactly the same one will run more than the other.
They specifically call out that you cannot parallel them.

 

[Quattrohead]

There is actually nothing wrong with these BMS at all.

 

[ericfx1984]

Unfortunately this is why you cannot parallel the contactor JBD BMS. Unless all the cells and all of the wire resistances and everything else is all exactly the same one will run more than the other.
They specifically call out that you cannot parallel them.

That's simply not an issue... Especially when you are sharing current between a pair of BMSs... The reality is as if they're even remotely close to balanced between each other The amount of current that flows between them is a non-issue

I've never had an issue with it at all on any of the other systems I've built... The fact that it continues to only cause a problem on this specific BMS and never on the other BMS tells me that the issue is with the BMS specifically

The reality is, sometimes stuff just fails. It sucks but it's what happens

There is nothing wrong with

As for this cock made me bull crap about making sure that you have exactly the same balance and this that and the other... Same lengths and resistance... It doesn't matter.

I actually did a massive imbalance of batteries in parallel... One battery was 15 kilowatt hours while the other battery in parallel was 6 kilowatt hours... The result, it just worked.

When charging, whichever battery had The most charged potential would be the one that would get the most current... Of course the smaller battery would typically charge up faster percentage wise... And as it reached a higher state of charge the charge would taper off of the smaller battery and go to the larger battery... Towards the end of the charge the smaller battery would be fully charged while the bigger battery would have a ways to go... And while it was not ideal it just worked. No major issues to speak of

I really do get tired of people claiming that you cannot have batteries in parallel... It just isn't true

 

[42OhmsPA]

Unfortunately this is why you cannot parallel the contactor JBD BMS. Unless all the cells and all of the wire resistances and everything else is all exactly the same one will run more than the other.
They specifically call out that you cannot parallel them.

Wow, I've had 4 in parallel for months, 3 in parallel for about a year and 2 in parallel for years.
2 packs are 230AH cells, 1 is 280Ah, 1 is 305AH. Wiring lengths are very close.
I haven't had a single issue besides the pack I didn't top balance going into protect a few times for a runner cell.

 

[42OhmsPA]

Well... It froze again

What I've noticed is each time that it has done this I've been charging the batteries using the EG4 chargeverter at night

In the morning I noticed that the battery that did not stop discharging / charging was down around 50% and the one that did stop charging / discharging It was still registering at 100% But was down around 53.9 volts

When I started the charge router up, all the power went to the battery that was at 50ish percent... But if I disconnect and reconnect the small balance cable on the battery that was not discharging / charging Then it would start charging, but only a very small charge before it came back up to 100%, while the majority of the charge current would go to the 50% battery

I suspect this BMS is going to fail. I think it's time to order another one and just leave this as a questionable backup



View attachment 258710

Looking at your voltages I bet what it happening is cell 3 is causing the BMS to go into protection for high cell voltage.
Try reducing your charge voltage to 54.8V or a bit less and monitor it. I'd also reduce current to 50A or less.

 

[Quattrohead]

OK knock yourselves out and have fun.
Obviously, I talk bollocks all the time and love to look stupid in public.

 

[ericfx1984]

Looking at your voltages I bet what it happening is cell 3 is causing the BMS to go into protection for high cell voltage.
Try reducing your charge voltage to 54.8V or a bit less and monitor it. I'd also reduce current to 50A or less.

It's possible... I may do another high amp charge and just watch it to see what happens

 

[ericfx1984]

OK knock yourselves out and have fun.
Obviously, I talk bollocks all the time and love to look stupid in public.

Oh come on don't be like that

 

[Quattrohead]

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

 

[fnnwizard]

Looking at your voltages I bet what it happening is cell 3 is causing the BMS to go into protection for high cell voltage.
Try reducing your charge voltage to 54.8V or a bit less and monitor it. I'd also reduce current to 50A or less.

It's this. Go into parameters and see what OVP for the cell level is at.
If you tap on the cell icon itself, it should give you a graphical history of V.

Notice that cell three is balancing while others are not. Not sure what your V or mV delta to start balancing is. Lower the charge current way down so you can give that cell time to discharge.

This is relatively easy to fix since it's 1 high cell compared to a pack with 1 low cell.

 

[42OhmsPA]

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

Try the data sheet here.

 

[42OhmsPA]

It's possible... I may do another high amp charge and just watch it to see what happens

Do a low amp charge.
See post 8 from @fnnwizard

 

[Quattrohead]

Data sheet and manual do not agree on series/parallel capability, I guess we are both right and wrong.

"2. The battery pack can be used in series, but the total number of strings after series is required to be less than
or equal to 32."

 

[Quattrohead]

You could try to copy the settings from the BMS you are happy with and paste them into the other using the Xiangxiang app.
Then you know all settings are 100% the same.

 

[sunshine_eggo]

OK knock yourselves out and have fun.
Obviously, I talk bollocks all the time and love to look stupid in public.

I thought you were quoting me for a second...

 

[42OhmsPA]

Data sheet and manual do not agree on series/parallel capability, I guess we are both right and wrong.

"2. The battery pack can be used in series, but the total number of strings after series is required to be less than
or equal to 32."

Gotta love clear chinese documentation.

 

[fnnwizard]

It's this. Go into parameters and see what OVP for the cell level is at.
If you tap on the cell icon itself, it should give you a graphical history of V.

Notice that cell three is balancing while others are not. Not sure what your V or mV delta to start balancing is. Lower the charge current way down so you can give that cell time to discharge.

This is relatively easy to fix since it's 1 high cell compared to a pack with 1 low cell.

Actually, you have to tap on the double up arrow first, which brings you to anohter page, then tap on the cell icon and it will bring up V history. I'm pretty confident it has hit Over Voltage Protect (OVP) and pack is not allowed to charge.

The double clock icons to the right of that shows charging history and high/low cell V too.

 

[ericfx1984]

It's this. Go into parameters and see what OVP for the cell level is at.
If you tap on the cell icon itself, it should give you a graphical history of V.

Notice that cell three is balancing while others are not. Not sure what your V or mV delta to start balancing is. Lower the charge current way down so you can give that cell time to discharge.

This is relatively easy to fix since it's 1 high cell compared to a pack with 1 low cell.

That is super useful. However it didn't show me anything I didn't expect as I have spent a lot of time watching this pack

 

[fnnwizard]

That is super useful. However it didn't show me anything I didn't expect as I have spent a lot of time watching this pack

View attachment 258952

View attachment 258953

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?