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ODD issue with EVE280ah cell with JBD BMS

BigDean

New Member
Joined
Dec 8, 2020
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27
This is my first build, so played it safe buying the cells from @Jenny Wu at Docan. 16 x 280ah EVE cells.

Built it as per the instructions with a JBD 100A BMS using the driver kindly provided by @Louisvdw and a Victron Multiplus II 48/5000.

All configured and appears to be working except I get a high voltage disconnect on Cell 1. Cell 1 is behaving very differently to the other cells. I suspect it is a dodgy cell but wanted to check with the experts first....

I checked all cells when opening and got these readings:

1/1 3.286
1/2 3.286
1/3 3.286
1/4 3.284
2/1 3.286
2/2 3.286
2/3 3.286
2/4 3.286
3/1 3.286
3/2 3.286
3/3 3.284
3/4 3.286
4/1 3.286
4/2 3.286
4/3 3.286
4/4 3.284

I haven't top balanced yet due to not having enough busbars.

When I first connected everything up, the charger kicked in and charged the pack up to 100% (according to the BMS). The BMS stopped the charge because cell 1 had hit the high voltage disconnect at 3.65v. All the other cells were still at around 3.4v.

I thought it was just an anomaly, so disconnected Cell 1 and used a load to bring the voltage down to the same as the others, 3.34. Connected all back up, and the BMS screen showed all within .001v. Then switched the Victron back on and within a few minutes, Cell 1 was back up to 3.65 and triggering the HV disconnect. All other cells are pretty much the same voltage at 3.357/8.

I left resting time of at least 10 minutes between all charges and discharges.

So, do I have a bad cell?

Thanks
 
To me seems cell 1 more charged than others, so top balancing may fix it. When my small 50 ah cells get charged to 3.65, they will settle to around 3.34 After a few hours.

When you say not enough bars to top balance, I have done it one by one, slow process with 50 ah cells, and for the bigger ones, I assembled to a batttery, charged to 3.45 X the number of cells in the batteries. My batteries were 8 cells, but I only had busbars for 4, so I broke that battery down and put 4 cells in parallel twice. Charging, the 8S battery took 4kwh to get to 3.45 per cell, and from there three hours in with the cells in 4P on a 10 amp power supply set to 3.65.

EDIT: I forgot to mention the very important step of using a BMS while doing this. Also, besides the overall charge voltage, set the individual cell cutoff to less than 3.65. I set mine to 3.55. Was recommended to me to watch the single cell cutoff voltage actually work and cutoff and keep eyes on the BMS app until then.
 
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Don't do this without a suitable BMS. A small/cheap 4s BMS can be very handy for this purpose.
I left that important step out. I used an overkill BMS. If at all possible set the cutoff voltage quite low so you can test it. I forget off I skipped that test or not. My single cell cutoff voltage was set to 3.55 with the overall charge voltage of 3.45 Per cell.
 
Don't set your charger to 3.65 volts per cell. Set it to 3.60 or a lower value and let the BMS do it's thing. But that's a very long term way to get cells balanced. Don't short cut things. Do a full top balance.
 
This is my first build, so played it safe buying the cells from @Jenny Wu at Docan. 16 x 280ah EVE cells.

Built it as per the instructions with a JBD 100A BMS using the driver kindly provided by @Louisvdw and a Victron Multiplus II 48/5000.

All configured and appears to be working except I get a high voltage disconnect on Cell 1. Cell 1 is behaving very differently to the other cells. I suspect it is a dodgy cell but wanted to check with the experts first....

I checked all cells when opening and got these readings:

1/1 3.286
1/2 3.286
1/3 3.286
1/4 3.284
2/1 3.286
2/2 3.286
2/3 3.286
2/4 3.286
3/1 3.286
3/2 3.286
3/3 3.284
3/4 3.286
4/1 3.286
4/2 3.286
4/3 3.286
4/4 3.284

I haven't top balanced yet due to not having enough busbars.

When I first connected everything up, the charger kicked in and charged the pack up to 100% (according to the BMS). The BMS stopped the charge because cell 1 had hit the high voltage disconnect at 3.65v. All the other cells were still at around 3.4v.

I thought it was just an anomaly, so disconnected Cell 1 and used a load to bring the voltage down to the same as the others, 3.34. Connected all back up, and the BMS screen showed all within .001v. Then switched the Victron back on and within a few minutes, Cell 1 was back up to 3.65 and triggering the HV disconnect. All other cells are pretty much the same voltage at 3.357/8.

I left resting time of at least 10 minutes between all charges and discharges.

So, do I have a bad cell?

Thanks
balancing is a MUST ALWAYS !

start doing that and your problems should be history
 
You can place a load across that cell without going thru the hassle of disconnecting it ..... the manual method will work, but you will probably need to bleed it off more than you did.
After all .... that's all a passive balance BMS does, it just does it automatically.

As upnorthandpersonal asked ... what load was used?

I would use a power resistor so I could calculate the current ahead of time. An easy one is to use a 1 ohm power resistor .... then, the current will be equal to the voltage .... and the power will also be equal to the voltage. There are a lot of them on Amazon ... but something like this.
 
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balancing is a MUST ALWAYS !

start doing that and your problems should be history
I presume the built in balancing on the JBS BMS is not sufficient?

I could try and get the Victron to charge to 3.45v, then after getting more busbar, set it up as 16P on the bench PSU to 3.65v. The problem with that is that the problem cell is going to stop it as it will reach the 3.65v disconnect. How can I run this one down so it doesn't stop the whole charge to 3.45v?

Trying to go straight to 3.65v on a 16P config with the bench supply from where I am now (around 3.34v) will probably take weeks as my cells are 280ah.

Thanks for all of your input chaps.
 
This is my first build, so played it safe buying the cells from @Jenny Wu at Docan. 16 x 280ah EVE cells.

Built it as per the instructions with a JBD 100A BMS using the driver kindly provided by @Louisvdw and a Victron Multiplus II 48/5000.

All configured and appears to be working except I get a high voltage disconnect on Cell 1. Cell 1 is behaving very differently to the other cells. I suspect it is a dodgy cell but wanted to check with the experts first....

I checked all cells when opening and got these readings:

1/1 3.286
1/2 3.286
1/3 3.286
1/4 3.284
2/1 3.286
2/2 3.286
2/3 3.286
2/4 3.286
3/1 3.286
3/2 3.286
3/3 3.284
3/4 3.286
4/1 3.286
4/2 3.286
4/3 3.286
4/4 3.284

I haven't top balanced yet due to not having enough busbars.

When I first connected everything up, the charger kicked in and charged the pack up to 100% (according to the BMS). The BMS stopped the charge because cell 1 had hit the high voltage disconnect at 3.65v. All the other cells were still at around 3.4v.

I thought it was just an anomaly, so disconnected Cell 1 and used a load to bring the voltage down to the same as the others, 3.34. Connected all back up, and the BMS screen showed all within .001v. Then switched the Victron back on and within a few minutes, Cell 1 was back up to 3.65 and triggering the HV disconnect. All other cells are pretty much the same voltage at 3.357/8.

I left resting time of at least 10 minutes between all charges and discharges.

So, do I have a bad cell?

Thanks
First I would say TOP balance first.

If the issue still continues then the Internal resistance of that cell is different than the rest.

You can try and match it or get an Hel-Tek active balancer to keep them in balance.
 
When you received your cell’s they’re all the same voltage like 3.28 V in your case.
The SOC of these cell’s, while having the same voltage, are not all the same!!!

That’s why you need to top balance. Do a search with “top balance” in this forum to see how it’s done.

You could deplete cell 1 till it’s no longer causing the high voltage disconnect, but then there will be a next cell that’s causing the HVD and so on and on and on…….
 
60v bench power supply and copper busbar ordered.

Will charge up to 3.45x16 so 55.2v in 16S on the bench PSU then arrange in 16p and new busbar to top up to 3.65v.

Then put back on JBD/Victron see what happens.

Thanks again.
 
bit confused on why you would charge as at 55.2v to top balance as a series without a bms.

Wouldn't it be better to just parallel them and charge to 3.45, then 3.65v with the power supply, a lot simpler and you don't have the issue with a cell peaking over the supplied voltage, as you can in a 16s set up without bms
 
55.2 is 3.45 per cell in series. Charging to there in series, and then placing in parallel to 3.65 will change the total time needed top balancing from two weeks to about 2 days.

Will talked about pre-charging cells in series in one of his videos and was also recommended to me before my top balance.
 
i get that 55.2 volt is per cell in series, but if a cell is already high, it's not going to balance as safely as in parallel.

But i do agree there are time benefits, when it comes to larger cells, my next set of Eve 304ah will take a while, but i allowed time for that, and my current pack is operational
 
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