Multiplus 2 low battery alarm with jkbms (Configure victron and jk-bms voltages)

I can still change them according to my measurements, but I think they allready match pretty close.

If your BMS settings are the same as in your last screenshot, and the cable loss is 0.15V, as you said before.

Your values ​​are as follows:

Bookmark Inverter
Victron DC input low shut-down = (2,7 * 16)+0,1 = 43,30
Victron DC input low restart = (2,8 * 16)+0,1+0,15 = 45,05
Victron DC input low pre-alarm = (2,8 * 16) +0,2+0,15 = 45,15

ESS assist.
Sustain voltage = 47,5
Dynamic cut-off 0.005C = 45,1 (your calculate correct)
Dynamic cut-off 0.25C = 44,2 (your calculate correct)
Dynamic cut-off 0.7C & 2C = 43,30

UPD: :warning: This is not template settings for other installations!

Are these measurements for these values measured by the Victron itself, or are they used as received from the BMS?

You should enter these settings into the configuration file “Bookmark Inverter” and the ESS assistant.

Yes I understand.

But I think cable loss should not be in the DC input low values, because the voltage will be lower and not higher when the maximum current flows (voltage drops, it doesn’t rise).

Or do I make a mistake here?

Make adjustments and enjoy, everything will be fine :wink:

UPD:
You measured your losses under load, they are within the specified values.
Your critical voltage is 43.45V
Victoron will work first.
Therefore, you have a wide range of battery capacity usage without harm or BMS shutdown.

:warning: Any changes in the BMS values: UVPR & UVP
Entails the change of all values ​​above!!!

I substracted the 0,15 cable loss from the lowest values, because afaik cable loss doesn’t add voltage.

Yes, towards the current.:+1:
Test and watch the telemetry, I’m sure everything will be fine.

I made a mistake, I used 45 instead of 44 volts (which is 16 × 2,75) for my calculation:

0,005C = 43,98V
0,25C = 43,10V
0,7C = 41,50V
2C = 36,86V

I will correct it accordingly:

Bookmark Inverter
Victron DC input low shut-down = (2,7 * 16)+0,1 = 43,30
Victron DC input low restart = (2,8 * 16)+0,1+0,15 = 45,05
Victron DC input low pre-alarm = (2,8 * 16) +0,2+0,15 = 45,15

ESS assist.
Sustain voltage = 47,5
Dynamic cut-off 0.005C = 43,98 (your calculate correct)
Dynamic cut-off 0.25C = 43,3
Dynamic cut-off 0.7C & 2C = 43,3

No, no, that’s too deep.
Go back to the previous values.
With the remaining SOC, 20% at the peaks will be enough.
But I wouldn’t recommend discharging deeper than 15-20%.

This is quite enough.

I will almost never discharge lower than 20% (it’s my DESS minimum) but only in case of a grid failure, which happens sporadically here in the Netherlands.

That is based on a cell voltage of 2,81 volts, not 2,75 volts. But that is still sufficient, I will change it back.

Work with optimally careful values.
If you have a significant capacity deficit, then it is worth considering the possibility of expanding the battery bank.

I’ll do, thank you for your support, I learned something new, thanks!

You are welcome. :wink:

1 Like

Note: just a reminder. Don’t go above 0.5C or you’ll slowly kill your MB31 cells.

1 Like

Yes I saw the specifications, but I can only draw 90 amps so I’m safe.