Daly Smart BMS stops charging randomly

[Freeman656]

Hi again,
I've a charging issue with my Daly (LifePo4 16S 150A Smart BMS). It's a new system that I have so I can't tell that it worked earlier and not any more.
Everything is online and 95% working fine for a few days now and each day the BMS stops charging around 70-75% SOC.
My system consists of a
- Multiplus II 48/5000
- Solarpanels (not really relevent in this case because they are AC coupled)
- CerboGX
- SmartShunt
- 16S / 280Ah battery
- Daly Smart BMS 16s LifePO4 150A
- All sorts of fuses everywhere....

I don't really know what to explain more, all the system is charging fine, and the second after, the BMS stops charging (the Chrg MOS is off) without any information (no overvoltage or anything in the SmartBMS App). This happens every day during the charge, at random SOC (mostly above 70%).

I still have access to the BMS, and just need to restart it using the app and it's working fine again.

Any thoughts why this would happen ?

 

[MisterSandals]

Any thoughts why this would happen ?

Can you post some pics of your BMS settings? And maybe a screenshot of the BMS status when this happens?

 

[Freeman656]

Hi MisterSandals !

Here we go, all the settings .
When the problem appears, only the Chrg MOS is off, amps are 0 and the rest is still the same.

Thanks

 

[Freeman656]

It happen again, right after I took the screenshots, not touched anything in the settings...

 

[MisterSandals]

The battery looks terrific as its perfectly balanced and close to 100% full.

The pic shows that when charge current jumps to 49A, the voltage spikes up to almost 59V. This looks odd. Why does the charging spike like this?
Are there any logs or info in the CerboGX?

What happens if you limit the charge amps to 25A?

 

[Freeman656]

Yeah the battery just had a top balance a few days ago, so... still quite well balanced
I guess the voltage spike is just after the BMS shutdown because the multiplus is around 58-60V when no battery is connected.
Nothing shows up in the CerboGX, the Multiplus just goes into Absorption mode after this event.

I'll try to limit the charge current to 25A in the MPII, I'll let you know !

 

[MisterSandals]

Looking closer, it looks like you were charging at 49A for a while, the the battery voltage spikes for some reason. Maybe the BMS is protecting it from going higher. If you measure the battery voltage when this happens, does it measure with a meter at 58-60V?

because the multiplus is around 58-60V when no battery is connected.

What do you mean the MP when no battery connected? Do you mean when BMS cuts out?

Can you post a pic of your battery wiring? Is everything tight?

 

[Freeman656]

What do you mean the MP when no battery connected? Do you mean when BMS cuts out?

Yes I mean when the BMS cuts out my theory is that the MP goes into this 'no battery' mode and is floating an ~58V which is measured by the smartshunt but maybe I'm wrong with this interpretation...

I can post a pic, but the battery layout is quite standard and everything has been tightened with the appropriate torque.

 

[MisterSandals]

MP goes into this 'no battery' mode and is floating an ~58V which is measured by the smartshunt

I cannot understand how your pic in post #1 shows battery voltage at only ~54.5V and then a minute later its 58V. And stranger still, the battery remains at 58V after the BMS cuts out.

Looking very closely at the graph, i cannot tell if the current drops first or if the voltage spikes first, or whether they happen at the same time.
Something is happening, i cannot tell what.

I would start simplifying. I take it that the CerboGX is controlling the MP?

- Solarpanels (not really relevent in this case because they are AC coupled)

This is an unknown for me. I actually never heard of anybody AC coupled with a MP before.
It must be a big array close to 3kW? Microinverters?

 

[Freeman656]

I cannot understand how your pic in post #1 shows battery voltage at only ~54.5V and then a minute later its 58V. And stranger still, the battery remains at 58V after the BMS cuts out.

The smartshunt show 58V but the BMS shows 53.6 after the shutdown (pic from the post #4). I guess on the battery side of the BMS it's ~54V and on the MP side it's 58V but why...

Looking very closely at the graph, i cannot tell if the current drops first or if the voltage spikes first, or whether they happen at the same time.
Something is happening, i cannot tell what.

I'm also in the dark concerning the timing of events...

I would start simplifying. I take it that the CerboGX is controlling the MP?

Yes it controls some part of it but not everything, I still use the VEConfig app to configure the abs/float voltage and ESS assistant.

It must be a big array close to 3kW? Microinverters?

6kW 9*APS microinverters with grid feed in (mesured by the MPII using the external sensor on the main AC. I'm in France, so it's 1 phase 240V.

 

[MisterSandals]

One thing i see is that your charging voltage is 58V (3.625Vpv) and your BMS is setup to cut out at 3.60Vpc.
What happens if you set your CerboGX/MP to charge at 57V?

 

[Freeman656]

Is this possible ? I haven't seen any charge voltage parameter for now, the only voltages I can modify are the abs/float.

In the DVCC I think there is a parameter for charge voltage, but am I in a DVCC environment ? (DVCC is not active right now)

 

[MisterSandals]

Yes, try absorb 57V.

 

[Freeman656]

Absorb is 56.8 right now in VE config and float is 54V.
When you say yes, you mean I activate DVCC ?

 

[MisterSandals]

Absorb is 56.8 right now in VE config and float is 54V.
When you say yes, you mean I activate DVCC ?

No, i do not know what DVCC is.

If your absorb is 56.6V, where is the 58V+ coming from?

 

[Freeman656]

I absolutely don't know !
I zoomed in the graph, and we can see that just after the spike, the voltage goes back to 56.8, which is the absorb voltage.
But we still don't know what causes this spike and also, why the BMS stays in some sort of safety mode even after the MP goes back to 56.8 !

 

[gnomie]

Since you are using grid tied microinverters the power source is the grid rather than the batteries or the panels. Your controller/inverter/charger must be pushing 58V to the batteries which the BMS is reading as a hot charge and shutting down the charge cycle. Reduce any charge parameter that is set to over 56V on your controller/inverter/charger then test the battery bank with a voltmeter on the trunk + and - while in charge mode. If you see anything over 56V then you controller/inverter/charger is defective and should be replaced. Your BMS is doing its job and preventing an excessive voltage from damaging your batteries.

 

[Freeman656]

Reduce any charge parameter that is set to over 56V on your controller/inverter/charger then test the battery bank with a voltmeter on the trunk + and - while in charge mode

I would like to, but I see nowhere any configuration above 56.8 (which is Absorbtion). Neither the Cerbo nor the MPII.
Of course I'm glad that the BMS is shutting down to prevent any damage !

Not sure if related but I found this post : https://community.victronenergy.com...pikes-with-victron-multiplus-and-lithium.html

 

[Ampster]

I would like to, but I see nowhere any configuration above 56.8 (which is Absorbtion).

Is there a calibration issue? If I understand the thread correctly, it is putting out 58 volts but is set at 56.8. Try setting it lower and see if that changes or check for other settings which might be causing that.

 

[Freeman656]

No really, the 58V seems to be during the bulk phase.
The absorbtion is right at 56.8 (see graph after 13:30), and the float is at 54V (no in the graph, but I can confirm).