BMS turns-off and not turn-on again after discharge

[kovinka]

Hi,
i have an installed by local company an inverter 6kW 48V, BMS JK and LiFePO4 battery, the problem is - when battery discharged to min voltage (46.7V - checked in DessMonitor) - it doesn't turn-on to charge automatically.

Inverter battery params:

• Battery Cut-off voltage: 46V
• Bulk charging voltage: 57V
• Float Charging Voltage: 56.5V

BMS params:

• Cell OVP: 4.18V
• Cell OVPR: 4.15V
• Cell UVPR: 3.5V
• Cell UVP: 3.4V
• Power Off Vol: 3.3V

Battery LiFePO4: 14 cells, 180Ah

Is it some configuration problem or where to start researching?

 

[BentleyJ]

Thanks for posting the Inverter & BMS parameters. Looks like the problem is in the settings.
Normal LFP cell voltage operating range is 3.0V to 3.4V. 90% of the storage capacity is within these limits.

Are the cells actually LiFePO4 or Li-ion? 14 LFP cells is not really a 48V battery, its only 44.2V nominal and the BMS parameters are WAY too high. Dangerously high actually.

Please clarify the number of cells and the cell chemistry. EDIT: Seems like the settings on the BMS are for a Li-ion type battery.

The following would be typical settings for a 16 cell LFP battery.

Inverter battery params:

• Battery Cut-off voltage: 48V
• Bulk charging voltage: 57V
• Float Charging Voltage: 54.4V to 54.8V

BMS params:

• Cell OVP: 3.65V
• Cell OVPR: 3.55V
• Cell UVPR: 2.8V
• Cell UVP: 2.6V
• Power Off Vol: 2.5V

 

[kovinka]

Thank you! When company installed, they said it's LiFePO4 and i cannot open the box - it's sealed:


When i connected to BMS via app, i see next screen - it says 14 cells.



I've asked the company for this problem, but looks like they don't want to help with it at the moment and/or investigating it - no response from them yet.
It's possible that it could be Li-ion battery, they didn't provide any documents about battery type. Not going to unbox it untill some response from them and trying to identify the problem first on my side.
Also read about LiFePO4 battery voltage, that should be 2.8-3.65V set, and wondering about it that it's too high.

 

[DIYrich]

Any pics of the model name of the battery? Any other identifying marks?

 

[400bird]

Your battery settings in post one and the screenshot in post #3 don't match Lifepo4 settings.

By the voltages in the screenshot, I'd say you have "regular" not Lifepo4.

In normal operation, the inverter should stop before the BMS disconnects the battery. Can you check your cell voltages and pack voltage next time the BMS disconnects?


Right now the BMS disconnects at 3.4 x 14 = 47.6
But the BMS tries to continue discharging to 46 volts.
There's your issue.

I'd raise the inverter under voltage threshold.

 

[BentleyJ]

Thank you! When company installed, they said it's LiFePO4 and i cannot open the box - it's sealed:
View attachment 164639

When i connected to BMS via app, i see next screen - it says 14 cells.

View attachment 164638

I've asked the company for this problem, but looks like they don't want to help with it at the moment and/or investigating it - no response from them yet.
It's possible that it could be Li-ion battery, they didn't provide any documents about battery type. Not going to unbox it untill some response from them and trying to identify the problem first on my side.
Also read about LiFePO4 battery voltage, that should be 2.8-3.65V set, and wondering about it that it's too high.

It appears to be a Li ion type battery with a nominal voltage of 3.7V per cell.

 

[DIYrich]

Looks like a 14 cell li-ion, not LiFePO4.

Raise the inverter battery cutoff to 49.0v. The inverter should stop before the bms.

Regarding charging: what inverter do you have? There are inverter settings that control when to charge.

 

[kovinka]

Thank you all for your answers!

Any pics of the model name of the battery? Any other identifying marks?

no, unfortunately any. All is inside the box and there is no any names/marks/etc on it. Only BMS qr code on it, that leads to the app download/instruction website.

It appears to be a Li ion type battery with a nominal voltage of 3.7V per cell.

ok, then i'll ask the company about it to confirm it. It was agreed to install LiFePO4, but they could change it and do not update me.

Looks like a 14 cell li-ion, not LiFePO4.
Raise the inverter battery cutoff to 49.0v. The inverter should stop before the bms.
Regarding charging: what inverter do you have? There are inverter settings that control when to charge.

it's hybrid - Axioma ISMPPT BF DOU G 6000. Settings from device control (have access and can change these values):

In normal operation, the inverter should stop before the BMS disconnects the battery. Can you check your cell voltages and pack voltage next time the BMS disconnects?

Right now the BMS disconnects at 3.4 x 14 = 47.6
But the BMS tries to continue discharging to 46 volts.
There's your issue.

I'd raise the inverter under voltage threshold.

Will do one more test with battery discharge and BMS turn-off and check the voltage of cells.
It's clear for me now why it disconnects.
Base on your responses, i will increase cut-off voltage to 49.0 and do one more test with it. Also, will try to clarify the battery type with a company (i guess it will be starting on Monday) and base on it decide how to proceed (if it's LiFePO4).

Thank you all! Will update the post with test result and other information i get.

 

[Supervstech]

I would first off adjust your inverter to never discharge below 47V
Adjust your charge controller to never charge above 58V
But I would also contact the manufacturer of thw battery and argue it is NOT LIFEPO4...
You paid for LFP, you should get LFP...
liNMC is only good for around 500 charge cycles...

And it can explode, and spontaneously catch fire...

Not to be used without SPECIFIC charge and discharge settings configured.

 

[kovinka]

Hi all! Short update on this topic - you were right, i have Li-ion battery installed.
Had a call with a company today - they confirmed it and promised to replace with LiFePo4 in few days for free. They had to install LiFePo4 battery and it's also what they provided in their booklet with prices and description (incl. LiFePo4) in the beginning.
Later, after it will be replaced and configured, i'll re-check if correct voltage settings are set in bms and inverter, as i don't trust them much now. Hope everything will work correctly.