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stevelectric avatar image
stevelectric asked

What signal should my self made BMS set in dbus to make the system go to passthru

Hello all, I'm currently coding a python module for Cerbo which talks to my BMS and relays the data into the dbus. This works nicely but in case of battery alarms or communications breakdown I can't trigger the system to go into a safe standby.

I tried

dbusservice['/State'] = 10
dbusservice['/ErrorCode'] = 17
dbusservice['/Io/AllowToCharge'] = 0
dbusservice['/Io/AllowToDischarge'] = 0
dbusservice['/Alarms/InternalFailure'] = 2

This makes the Cerbo beep and show two alarms, but the Multiplus II happily goes on inverting. Even worse, if the SoC gets updated as 0 into the dbus, the MP starts charging full throttle from AC.

The dbus manual says "When a dbus service cannot communicate anymore with its direct counterpart, the process will disconnect from the D-Bus" but doing that leaves me no possibility to signal alarms to the user.

I would like to send the whole ESS system into passthru and show an alarm message.

Does anyone have suggestions which values I should set in the dbus?

Thanks and kind regards

Stefan

P.S. ESS configured "optimized without BatteryLife", with external meter, MPPT, DVCC off.

ESSBMSpython
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6 Answers
ad-le-roux avatar image
ad-le-roux answered ·

I was looking for the same thing, have a look at: https://www.victronenergy.com/live/ess:ess_mode_2_and_3
Section 6.1

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Louis van der Walt avatar image
Louis van der Walt answered ·

If you set DVCC to ON then the GX will listen to what the battery request.

Then if you set /Info/MaxDischargeCurrent =0 it should switch the MultiPlus off as you told it not to discharge the battery anymore. When the SOC has recovered again the Multi will start up automaticly again.

Rather keep the SOC to the actual value. Don't set it to 0 if it is not zero as this might trigger other events.

See https://github.com/Louisvdw/dbus-serialbattery/blob/master/etc/dbus-serialbattery/dbushelper.py for all the paths that my serialbattery driver propulates, if that helps you.

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stevelectric avatar image stevelectric commented ·

Louis, thank you for the advice and the look into your source code. I hoped to implement the DVCC support at a later stage but seems like I can't :-)

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johanndo avatar image
johanndo answered ·

If you want it on pass-trough, you have to disable the inverter and set the charger to 0A. Then it has no other choice as to pass-through.

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pvpax avatar image
pvpax answered ·

Hi!

/Settings/CGwacs/MaxDischargePercentage and /Hub4/DisableCharge work for me to trigger passthru from node red. Setting charge current to 0 did not work, there was always a small current flowing to/from the battery.

Not sure how those will affect your MPPT as I don't have any in my system.

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johanndo avatar image
johanndo answered ·

You have to enable the 2 wire BMS assistant, so the multiplus / quattro reacts on the BMS messages.

Io/AllowToCharge

Io/AllowToDischarge

are digital input readings.

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stevelectric avatar image
stevelectric answered ·

Thank you for your answers! The com.victronenergy.vebus.ttyS4 service has

  • Hub4/DisableCharge
  • Hub4/DisableFeedIn

which make the MP2 go into pass thru when set to 1.

Since I dont like the BMS to mess with the ESS/MP2 settings directly, I will try also to implement DVCC support.

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