Will this balance eventually?

[tiger37373]

Have had these running for about a week, now. Do you think that this will balance eventually? All seem to be connected well.

 

[Bob B]

They are all pretty good except that one low cell .... I don't think the JBD BMS has very much balance current.

If you have a power supply I would remove that charge from the pack and connect the power supply to that on cell by itself set at the same voltage as the other cells.
No need to disassemble the pack, just give that low cell some boost.

 

[J.P.]

Is that correct? You have 200Ah with just 4 cells?
I have several JBD BMS's (really like them so far) but my App is on the iPhone so I am not familiar with your screen but is Balancing even enabled? It says "Balance closed" on that screen.
Also, I have the choice b/t enabling balancing "all the time" and "only on charge" and there is also a setpoint voltage in which it is enabled. If you mess with those settings you can get a lot more balancing out of it depending upon the settings.

 

[JeepDaddy]

Did you top balance your cells before assembling your pack?

If you have a power supply I would remove that charge from the pack and connect the power supply to that on cell by itself set at the same voltage as the other cells.

And this^^^^

That cell is pretty far out for a BMS balance function to be effective.

 

[mikefitz]

Its not that far off. No need to dismantle the battery, either boost up that cell or drain the high cells (car headlight bulb).
Best check with a meter direct on the cells to confirm there is no connection or BMS issue.

Mike

 

[Bob B]

Best check with a meter direct on the cells to confirm there is no connection or BMS issue.

Mike

Good point ^^^ .... you should verify the cell voltages with a meter.

 

[time2roll]

No. I don't think that one low cell will balance any time soon enough.

You need to top charge that cell separately. Or discharge the other three cells down to that level.

If the low cell was maybe 3.42 I might say let it go a bit but not 3.367

 

[time2roll]

OK if you can turn off the balance only when charging function. It will do some but still going to be a while.

 

[tiger37373]

It looks as if my bms isn't actively balancing on the line to that cell. All the wires are well connected and test consistently. When I reset in driving mode it went into active balance on all cells, except that one.

 

[time2roll]

I believe that is correct. BMS will bleed down the three to the lowest level. Then you charge them all back up when the balancing stops.
May need to drop the balance start voltage to 3.360 to go all the way down.

 

[GSXR1000]

It looks as if my bms isn't actively balancing on the line to that cell. All the wires are well connected and test consistently. When I reset in driving mode it went into active balance on all cells, except that one.

BMS don't charge low cell.. it bleeds the other cells... also a BMS doesn't do much on large cells... it would take months or years

as asked before did you to balance before you built them?

also I bet in the 13.3v area they are very close.

last I agree you could every day charge the lowest cell to the voltage of the highest cell (don't set power supply any higher then that.. and that won't be protected by bms so I would say do a little at a time

 

[Hedges]

Since there aren't one or more cells showing over-voltage by a total of 0.2V to go along with the one under-voltage by 0.2V, less likely it is poor/floating balance lead. But go ahead and double-check each cell with a meter. Probing cell terminals themselves if possible rather than busbar, cable terminal, or stud.

One cell low and three cells high. SoC vs. voltage more distinct further up the curve.
Rather than discharging three well balanced cells and ending up with four cells of varying SoC, charge the one low cell to 3.58V, disconnect and let it settle. If it settles lower, charge the cell a little higher (not to exceed 3.65V) and let settle again to end up balanced with the others.

 

[tiger37373]

BMS don't charge low cell.. it bleeds the other cells... also a BMS doesn't do much on large cells... it would take months or years

as asked before did you to balance before you built them?

also I bet in the 13.3v area they are very close.

last I agree you could every day charge the lowest cell to the voltage of the highest cell (don't set power supply any higher then that.. and that won't be protected by bms so I would say do a little at a time

No, I didn't balance before assembly. The overkill cells are advertised as being top balanced before delivery. I do not have a secondary way to charge an individual cell, in any case. I would have to buy a small charger.

 

[tiger37373]

Is that correct? You have 200Ah with just 4 cells?
I have several JBD BMS's (really like them so far) but my App is on the iPhone so I am not familiar with your screen but is Balancing even enabled? It says "Balance closed" on that screen.
Also, I have the choice b/t enabling balancing "all the time" and "only on charge" and there is also a setpoint voltage in which it is enabled. If you mess with those settings you can get a lot more balancing out of it depending upon the settings.

Yes, they're arranged in an 8 cell pack, parallel and series.

 

[tiger37373]

Its not that far off. No need to dismantle the battery, either boost up that cell or drain the high cells (car headlight bulb).
Best check with a meter direct on the cells to confirm there is no connection or BMS issue.

Mike

I checked all the connections are in order and we'll connected, all the way to the plug on the bms.

 

[time2roll]

Did you let it balance overnight? What are the voltages this morning?

 

[GSXR1000]

I will say no cells from china are balanced.. at least to each other.. prolly are charged in groups but who knows

and yes it says balanced from the factory which isn't over kill it is china.

I don't get as much as we spend on cells what is the big issue with spending 60 on a power supply

 

[tiger37373]

I will say no cells from china are balanced.. at least to each other.. prolly are charged in groups but who knows

and yes it says balanced from the factory which isn't over kill it is china.

I don't get as much as we spend on cells what is the big issue with spending 60 on a power supply

View attachment 51664

It's not the cost, I just don't have a unit available. Honestly, all the other units were right on and balance perfectly, so I got unlucky on one... It's obvious, now that I should have gone through the whole process. Still learning a lot. I'm currently letting them balance by the discharge method and we'll see how the bms acts after that.

 

[tiger37373]

It's not the cost, I just don't have a unit available. Honestly, all the other units were right on and balance perfectly, so I got unlucky on one... It's obvious, now that I should have gone through the whole process. Still learning a lot. I'm currently letting them balance by the discharge method and we'll see how the bms acts after that.

Got them down to within .02v And the bms just ignores the low cell during balance. It just pushes the other three right back up to 3.6, is this like I suspected that the bms doesn't work properly?

 

[Bob B]

That is within 20 mv and is perfectly fine. The BMS should have a delta to balance setting and is probably set at 20. If you want to balance tighter you would have to reduce that number.