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jsmvanwyk avatar image
jsmvanwyk asked

BSL Battery doesn't fully charge, stuck on 87%

Good day, a Victron 3 phase system with 2 x 5.1 kWh BSL batteries is behaving very peculiar.

Until recently, it was fully functional but suddenly it started to behave such that when the battery is being charged it will stop to charge between 85% to 87% SOC. And no matter what we do it will not charge further either from PV or from the grid. It appears as if the BMS is stopping charging at this point and we cannot figure out why.


We have verified all settings as per Victron instructions for the BSL batteries and have upgraded to the latest firmware on the Cerbo, Quattro's and MPPTs and it had no effect.


We have reached out to the battery supplier as we believe it is probably the BMS or the battery that is faulty but I thought it prudent to check the forum here if anyone has come across something like this?

Below is a screenshot taken right now when there is full sunlight and more than enough PV available.

Kind regards

Marius

1646043624579.png

SOCbslbatt
1646043624579.png (232.1 KiB)
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Alexandra avatar image Alexandra ♦ commented ·

@jsmvanwyk

Chances are the bms is telling the system not to charge there possibly is a problem in the battery.

I have not used BSLBATT, but there are few things to check.

Are all the cells in balance? What is State of Health? Has all the charge/discharge been done within the battery pack capabilities?

If you run them "dumb" on a stand alone mppt does it charge?


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jsmvanwyk avatar image jsmvanwyk Alexandra ♦ commented ·
Thanks Alexandra,

I agree, I think there is one or more cells with an issue. State of health is 100% according to the data available and all charge/discharges was done in line with battery specifications.

Kind regards


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6 Answers
nickdb avatar image
nickdb answered ·

BSL batteries charge to 54.5 V, yours is well beneath that - but you say you have checked settings. I would double check.

Get your installer to read the logs from the BMS as it shouldn't stop charging below 54.5V.

If you drop the grid connection does it start to charge?


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jsmvanwyk avatar image jsmvanwyk commented ·
HI, settings are fine, (and battery used to charge to 100%) . Awaiting logs to see. Wrt to dropping the grid, tried that but it still only charge it to 87%
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snoobler avatar image
snoobler answered ·


IMHO, this is a slight imbalance issue coupled with a big BMV sync issue.


15S @ 54.1V is 3.61V/cell - well into the upper leg and very very near full charge voltage.


If possible, verify the cell voltages when the charging is cut off.



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jsmvanwyk avatar image jsmvanwyk commented ·
Thanks, I agree. Will check individual cell voltages
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pedaaa avatar image
pedaaa answered ·

BSL 100Ah is 16s

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snoobler avatar image snoobler commented ·
Couldn't find a datasheet and was going off the 54.5V charged voltage mentioned above.
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pedaaa avatar image
pedaaa answered ·

Hello,

has there been any news? I just ordered my BSLBatt units, so i´d be happy, if there was an solution or reason found to this issue?!

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nickdb avatar image nickdb ♦♦ commented ·
The 100 and 125AH batteries have been widely used without issues. I wouldn’t worry about it.


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jsmvanwyk avatar image jsmvanwyk commented ·
Hi, as soon as we identify the final outcome I will post it here

Regards


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tom4x avatar image tom4x jsmvanwyk commented ·

Did you find out the reason?


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nickdb avatar image nickdb ♦♦ tom4x commented ·
The only thing that will prevent charging is if the BMS intervened. You can buy a bsl cable online and use PBMS tools to read bms data, which will provide more insight.

This should also be reported by charge limit parameters in the GX details tab.

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pedaaa avatar image pedaaa nickdb ♦♦ commented ·

Could you please give some more details on this?! I am going to initiate my installation with BSL 100Ah Rack battery modules in apprx. 1-2 weeks.


why would the BMS stop charging here?

The standard recommended charging voltage regardign to BSL manual is 54,5V which means 3,4V per cell. Isn´t that quite low and safe?! Why would the BMS should even think about to intervene here? arn´t the BMS limits way higher?

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pedaaa avatar image pedaaa nickdb ♦♦ commented ·

Hello again,

do you know the Password, to be able to change parameters with PBMS tools? My BSL´s are super unbalanced. And it would help me if i can change some of those parameters.

But i guess BSL is not willing to give out the password? Are you willing to send it to me?! via other message-channel or similar?

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nickdb avatar image nickdb ♦♦ pedaaa commented ·

Don’t have it.

You can’t fix an imbalance by changing the bms.

It needs time on charge, unless you have a bad cell.

Can you share the min/max cell chart and the battery voltage chart?

Mine took 3months to balance, it was slow.


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pedaaa avatar image pedaaa nickdb ♦♦ commented ·

its clear for me, that i can´t balance by only changing BMS settings, no worry.

I have 9x 100Ah units. 8 are doing good so far. But 1 unit always got the cells with lowest and highest voltage. Beside those two cells, all other cells are pretty close in voltage.


But because of this one unit, i would always get high voltage alarm, if i try to fully charge the whole package. So i implemented a variable Modbus CVL, that prevents overcharing this one cell.

The BMS itself does not lower CVL, so it would always let you charge until a unbalanced cell hits 3,75V, which is way to high in my opinion. Thats more stress on a cell, than i would like to see.


Anyhow, this is the bad unit:

1661533627741.png


But even, if this one will balance in a few weeks,

the BMS parameters are not choosen well.

54,5V Full charge Voltage is clearly to low for a 16S LIFEPO4 battery.

How should this ever balance during normal operation? You need to allow higher voltage from time to time to let it top balance.

But this is hardly possible with a 54,5V CVL...


Also the Balance Threshold and differential voltage would be nice to modify. At least for the intital time until the batteries are somehow balanced.



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pedaaa avatar image pedaaa pedaaa commented ·


lowest and highest curves represent always the same "bad cells", within the same unit.

i also removed this "bad unit" for a while, which gives way nicer curves:

1661534441431.png


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pedaaa avatar image pedaaa pedaaa commented ·

@nickdb :

now i super slowly charged, but still the same happens. Also with the very same min. and max. cells:

one seems super full,

the other seems super empty.

and they won´t change so far.

1661689133231.png


How would you continue?!

Hold it at this stage?! Lets say hold the max. cell at 3,5-3,6V for 1-2 days? Hoping the min. cell to catch up?


Or would you rather prefer doing cycles, instead of holding constant voltage?


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nickdb avatar image nickdb ♦♦ pedaaa commented ·
Hi @Pedaaa

You have a bit of a gap there.

The BSL's are really slow. What does sometimes help, the importer recommends this, is to do a couple of deep discharge/charge cycles.

You should also leave it on the ESS "keep batteries charged" setting for a few days.

Once the difference narrows a bit, it will sort itself out.

As mentioned, mine took months.

If you look at the trend over time you will see it slowly improving.

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kees-barendse avatar image kees-barendse nickdb ♦♦ commented ·

Hello, I hope you are well. I am commissioning 11 5000 VA Easysolar systems each with 2 100Ah BSL LifePo4 batteries. You mentioned somewhere they are slow to balance? I have 5 of them running for a few weeks now and on all system, still, after reaching 100% SOC one or more cells rise to 3.55 VDC and stay there until the MPPTs run low on sun.

Should I just be patient? Many thanks!

1717495129876.png

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Fideri avatar image
Fideri answered ·

@Pedaaa

Did you ever resolve the problem? I'm interested because I have a slew of BSL batteries installed recently. So far they appear good, fingers crossed.

Fideri

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pedaaa avatar image pedaaa commented ·
Hello,

yes it was a faulty cell.

after a while talking back and forth with BSL, they send me a new pack of cells, and i replaced the faulty pack

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Fideri avatar image
Fideri answered ·

Noted. Thanks everyone.

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