How to change discharge current on voltronic 3-MPPT

[educorner]

Hi all, 

I have an older voltrinic tri-MPPT running firmware 75.31a connected to 2x pylontech 5000, PF is 0.8
I notice that when the load goes over 2000Watt the inverter is going from battery mode to line mode.

I use solarassistant as software, batteries are charged when electricity is cheap and with solar off course. 
I can't find any setting to set the discharge current, also tried with watchpower or the settings on the display. 

Is there any way to change the behaviour?  Even with full battery it goes to grid all the time....
The load should be going to 4000 Watt.

Edited September 30 by educorner

[Beat]

Battery discharge current is not determined by the inverter but by the load. Heavy load causes the battery voltage to drop due to internal resistance (Ri), the so called kettle effect. The changeover to line mode is controlled by the "back to utility source" setting (12) in Voltronic inverters. If you want to prevent it from happen too early you must lover that setting, presuming you have chosen SbU operating mode (01) and battery type USE (05). I have set it to 47V, when load shedding looms I set it to 48V (15 cells packs).

[educorner]

@Beat that is what i was thinking too but seems not to be true. The voltage is set to 47V but it happens also at 49.8 V. Lithium batteries doesn't have that voltage drop so I don't know why that happens...

[Beat]

9 minutes ago, educorner said:

Lithium batteries doesn't have that voltage drop

Oh yes, they do too. They may have lower Ri than same size lead battery but still. There is nothing in the world without resistance except at temperature 0°K.

15 minutes ago, educorner said:

but it happens also at 49.8 V

There must be something wrong in another setting or in the firmware.

[Coulomb]

See  FAQ #2. You need to set the cut-off voltage dangerously low. Fortunately, with most lithium batteries, there is a BMS to save the battery from excessively low voltage.

There is also the issue that the inverter's firmware doesn't compensate for the battery's internal resistance. Unfortunately, there is no patched firmware for this model that could help with that.

Do you perhaps have too small a battery for the intended load? Adding an extra battery module may help.

[Beat]

8 hours ago, Coulomb said:

there is a BMS to save the battery from excessively low voltage.

Different brands of battery have different BMS setting for this protection. The LEOCH specs set that limit to 40.5V (15 cells). That allows almost 100% DoD. I set the inverter low voltage cutout (29) to 42V and never had any problem.