Jan Olšaník avatar image
Jan Olšaník asked

Li-ion cannot discharge below 48V


We have adapted high voltage LG resu batteries to low voltage 48V for a Victron system using Seplos BMS. The limiting range of these Li-ion batteries is between 3 and 4.2 volts per cell. One battery pack contains 14 cells connected in series, so the voltage range of the pack is 42 to 58.8 volts.

Now we need to do several cycles from full charge to full discharge. Unfortunately, the Victron system will not let us go below 48V when discharging. We assume that the discharge is being stopped by the Victron because the alarm is coming from the VE.Bus system (276 instance).

System setup: 3x Multiplus II 48/5000, Cerbo GX, 2x SmartSolar MPPT 250/100 + 2x SmartSolar MPPT 250/60, adapted LG Resu Li-ion batteries 1764Ah with Seplos BMS (14 packs)

Inverter settings:

Inverter tab:

- DC input low shut-down = 42.00V

- DC input low restart = 43.00V

- DC input low pre-alarm = 43.50V

- shut down on SOC is disabled

ESS assistant settings:

- option "System uses LiFePo4 with other type BMS" is checked. Unfortunately there is no option for Li-ion batteries

- battery capacity is 1764 Ah

- do not change battery type

- sustain voltage 42.0V

- dynamic cut-off:

0.005C = 43.00V

0.25C = 42.66V

0.7C = 42.33V

2C = 42.00V

- restart offset 1.20V above cut-off

Of course we also checked the BMS settings, but there is nothing set to stop the discharge at 48V. All the limits are up to around 43V.

Does anyone have any idea what could be causing this early low battery alarm? Do we have something wrong in the settings?

Many thanks in advance for your valuable advice :)








MultiPlus Quattro Inverter Chargerlow battery warningess dischargingdischarge level
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1 Answer
Alexandra avatar image
Alexandra answered ·

@Jan Olšaník

That one mismatched battery with less cells will need to be removed. It will be crippling the rest of the system and you will do better without it.

Your system is shutting down because the battery is telling it to do so DCL/=0A means no discharge ... the bms is telling it to do that.

I would switch peak shaving to above min SOC anyway. You can't peak shave with 0%?

And you need to allow for cell imbalances at low SOC. So switch off at 5 or 7% SOC. Makes self recovery easier when the batteries don't switch off first.

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