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ODD issue with EVE280ah cell with JBD BMS

Comes to a technique about pre-charge versus not pre charge. I think the pre-charge is safer if done with the BMS rather than just leaving the cells on a power supply.

To me with the BMS, I can check the cell status frequently and see if they jump up. I don’t know individual cell status in parallel. As far as doing that and not being as safe in parallel, if the parallel voltage is set to 3.6, I don’t see how it’s dangerous.

The biggest reason I like the pre-charge first is my Dr. Meter 10 amp 30 volt power supply the voltage has wandered twice To too high. I can check frequently the status if the cells are only in parallel for three Hours, but IMO I can’t check very well two weeks straight Without the pre-charge. That may just be the Dr. Mater power supply, but I see that power supply is used more than any other power supply.
 
So far i haven't had any issues with my 10amp 30 volt wantek dc variable unit, or my EBC-A20 unit. but i guess its like any electrical unit out there, it can happen.

i just feel its safer parallel charging for top balance than in series, only because they should be charging at the voltage i want.

but if a BMS is used, it would put my mind at ease somewhat, for me i thought the OP was just going to wire it up at 55.2 volts without a bms, maybe i didn't read the post correctly

EDIT: i just re read the OP post, it does appear that he plans on putting the BMS on after he has charged up to 3.65 Volt in series then adding the JBD bms.
 
So far i haven't had any issues with my 10amp 30 volt wantek dc variable unit, or my EBC-A20 unit. but i guess its like any electrical unit out there, it can happen.
You’ve never seen this power supply voltage drift up slightly? I consider +/-.02 volts normal with the Dr. Meter. I’ve seen it drift as far as .6 volts twice putting it outside the parameters.

If so, thone two power supplies would be a better unit to start with. I’ve had a couple other people post that this Dr. Meter has wandered also.
 
@BigDean the driver will reduce the charge current when the SOC reaches close to capacity. But when you build the battery the BMS will start with a SOC that will not match the cells as it just does not know this. The JBD normally start at 0% SOC, but I think the JKBMS default to 50% SOC.
So any new BMS will need to adjust itself and will do that with the first few cycles.

Also as others have mentioned yours cells might not be all on the same charge level. You always will get one cell that reach full first. Lithiums jump very fast.

As the JKBMS has active balancers you can disconnect it and set it to balance the cells. Give if a few days. Then charge it again. If you can, don't put it into active use until you could top balance for a week.

For Victron's there is also anther option. As it works on voltages (Multi, MPPTs, batteries), you can just lower the voltage that the battery want until that one cell does not reach 3.65V anymore. The BMS balancer will then work it's magic to balance the cells, but you will be able to use the battery during this time as well. As the cells get balanced over the days you can increase this voltage.
1640704938685.png
Set it under DVCC by activating the Limit battery charge voltage and then lowering the value. I suggest you start with something like 3.35V per cell (thus 53,6V for 16 cells).
The smallest amount from this limit or the battery parameters will be used.
 
@BigDean the driver will reduce the charge current when the SOC reaches close to capacity. But when you build the battery the BMS will start with a SOC that will not match the cells as it just does not know this. The JBD normally start at 0% SOC, but I think the JKBMS default to 50% SOC.
So any new BMS will need to adjust itself and will do that with the first few cycles.

Also as others have mentioned yours cells might not be all on the same charge level. You always will get one cell that reach full first. Lithiums jump very fast.

As the JKBMS has active balancers you can disconnect it and set it to balance the cells. Give if a few days. Then charge it again. If you can, don't put it into active use until you could top balance for a week.

For Victron's there is also anther option. As it works on voltages (Multi, MPPTs, batteries), you can just lower the voltage that the battery want until that one cell does not reach 3.65V anymore. The BMS balancer will then work it's magic to balance the cells, but you will be able to use the battery during this time as well. As the cells get balanced over the days you can increase this voltage.
View attachment 77383
Set it under DVCC by activating the Limit battery charge voltage and then lowering the value. I suggest you start with something like 3.35V per cell (thus 53,6V for 16 cells).
The smallest amount from this limit or the battery parameters will be used.
Thanks again. I set it to 53.6 which was pretty much what the cells were at so quickly all looked good. Have now set it to 54.4 and will will let it do its thing. ?
 
Any chance you could swap cell position then try again, might just be a weak connection.

Also BMS does very very slow top balance.
 
You’ve never seen this power supply voltage drift up slightly? I consider +/-.02 volts normal with the Dr. Meter. I’ve seen it drift as far as .6 volts twice putting it outside the parameters.

If so, thone two power supplies would be a better unit to start with. I’ve had a couple other people post that this Dr. Meter has wandered also.
I can't say i have noticed them drift at all, I normally use my multimeter to double check at the start and then after 15 minutes and during the process

The EBC unit i run through my laptop, so i can keep an eye on them remotely if needed and it records the voltage.

+/-.02 volts i could handle, i couldn't trust it if it when .6 volts over.

Still i remember in the early days, people would charge up to 4.2 volts per cell and it wasn't the end of the world, just not great for long life.
 
Any chance you could swap cell position then try again, might just be a weak connection.

Also BMS does very very slow top balance.
Thanks for that. Now it is setup as above, the first cell normalised and now one of the others is all over the place.

As it stands I have no load on the inverter, so think I need to get the batteries cycled a few times as well.

Unfortunately I am away for all of January so am going to have to turn the system off and resume in early Feb.

Thanks all for your input.
 
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.
It's also explained in the how to top balance resource.

 
@BigDean the driver will reduce the charge current when the SOC reaches close to capacity. But when you build the battery the BMS will start with a SOC that will not match the cells as it just does not know this. The JBD normally start at 0% SOC, but I think the JKBMS default to 50% SOC.
So any new BMS will need to adjust itself and will do that with the first few cycles.

Also as others have mentioned yours cells might not be all on the same charge level. You always will get one cell that reach full first. Lithiums jump very fast.

As the JKBMS has active balancers you can disconnect it and set it to balance the cells. Give if a few days. Then charge it again. If you can, don't put it into active use until you could top balance for a week.

For Victron's there is also anther option. As it works on voltages (Multi, MPPTs, batteries), you can just lower the voltage that the battery want until that one cell does not reach 3.65V anymore. The BMS balancer will then work it's magic to balance the cells, but you will be able to use the battery during this time as well. As the cells get balanced over the days you can increase this voltage.
View attachment 77383
Set it under DVCC by activating the Limit battery charge voltage and then lowering the value. I suggest you start with something like 3.35V per cell (thus 53,6V for 16 cells).
The smallest amount from this limit or the battery parameters will be used.
Update time.

I have run the battery through a couple of discharge/charge cycles.

I just wanted to confirm what I am seeing is what is to be expected.

The Maximum charge voltage in DVCC is set to 55.2v, so 3.45v per cell. SOC is set to 20% which the Victron manages correctly.

The JBD app is set as per Overkills recommendations:

IMG_3211.PNGIMG_3212.PNG

When the battery is almost full, I get a lot of over voltage errors, which makes sense:

IMG_3210.PNG

Does this balancing look correct?

Thanks
 
This is fine. You want to give your balancer a lot of time at the top to balance.
All the settings look fine, but if you want to get it to balance without giving you overvoltage errors, you can lower your Maximum charge voltage in DVCC (55.0V or 55.1V should work). As you see that you don't get some cells going over 3.45V while others are still at 3.35V you can increase it more until you remove that. Lowering by a few mV should not have a big impact on your capacity.

From what I have seen, the JBD normally ballance the top 2 cells at a time. Yours show similar so that is fine. You want all your cells to look almost the same. So aim for 0.001V difference at around 100% SOC and then you know your cells are balanced. Just give it some time.
 
So aim for 0.001V difference at around 100% SOC and then you know your cells are balanced. Just give it some time.
.001 is pretty close. I have only used my battery and JBD BMS for about a month and I am happy with .006 - .015.

Again only had the BMS for about a month, but with such a flat charge curve the cells that 3.35 volts, I have no idea what the SOC is at except somewhere between 40% and 80%, but the cell that is 3.59 is in excess of 90%. With 280 ah batteries and the balancer function set to balance only above 3.4 volts and operating at perhaps 1 amp, there’s not a lot of time spent at this state for the battery to balance. For me my voltage deltas are not as drastic perhaps .015, but my battery may only spend an hour at a point where the cells can balance. So I suspect with a .23 volt difference, using the BMS function alone to take care of that difference could take a long time, like several weeks long.

My thoughts as new to lithium batteries would be may be time to either leave balancing on at all timed, or install an active balancer, charge the batteries to full and let the balancing function run for a couple of days.

I can only really say the most I’ve seen my cells voltage delta was .015 and I installed them a month ago and top balanced them first. That top balance took over a week, and I never want to dissamble my pack and do that again. I don’t enjoy top balancing or capacity testing.
 
This is fine. You want to give your balancer a lot of time at the top to balance.
All the settings look fine, but if you want to get it to balance without giving you overvoltage errors, you can lower your Maximum charge voltage in DVCC (55.0V or 55.1V should work). As you see that you don't get some cells going over 3.45V while others are still at 3.35V you can increase it more until you remove that. Lowering by a few mV should not have a big impact on your capacity.

From what I have seen, the JBD normally ballance the top 2 cells at a time. Yours show similar so that is fine. You want all your cells to look almost the same. So aim for 0.001V difference at around 100% SOC and then you know your cells are balanced. Just give it some time.
Thanks a million as always.
 
I'd keep an eye on it to see if the trend over time is that the cell delta voltage is less and less.
If the delta increases instead ... I'd be looking closely at all bus bar connections .... run some relatively high current tests looking for differences in voltage across connections or checking things closely with an IR test meter.
 
I'm only running 12v packs, but my understanding is that trying to manually balance cells with voltage readings is just never going to be good enough, due to the flat voltage curve, not to mention surface charge. Drawing from one cell while others may be charging will mean that they are not truly at the same SOC, no matter how accurate your voltage readings are. A top balance is really the only way to truly balance. Now, I did connect my cells into packs with BMS, and put an initial charge on them because I am totally off-grid, and my array can charge 7 times faster than my bench top ps can. Once my pack was as full as possible, I took them apart and reconfigured for parallel balancing. It made the TB go much faster. But you simply cannot draw any useful conclusions until you've done a proper TB. IMHO.
 
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