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Version 3.1 (beta)

Attention: This is my first experience with the Victron system. I offer it "as it is" for persons with sufficient knowledge and experience and under exclusion of any kind of liability. You should review and understand the code before using it. Please read carefully the explanation of all parameters in settings.py. None of them is universal, you have to adapt everything to your system.

My hardware:

  • 1x MultiPlus-II 48/5000/70-50
  • 4x BlueSolar MPPT 100/20
  • 6x APSystems DS3
  • 1x LiFePo4 battery 16S with BMS JK-B2A24S

Please report the bugs and propose improvements. Many thanks to all who already participated. According previous experience I prefer if you attach a piece of code instead of creating a merge request. And please understand, that I'm not able to include all proposals, this would make the program too complex and difficult to maintain.

Installation:

  • create /data/dbus-aggregate-batteries directory
  • copy the stuff into it
  • set chmod 744 for ./service/run and ./restart
  • set the parameters in ./settings.py (please read comments to understand the function and adjust the parameters)
  • write initial charge guess (in A.h) into ./charge
  • add command ln -s /data/dbus-aggregate-batteries/service /service/dbus-aggregate-batteries into /data/rc.local

The service starts automatically after start/restart of the Venus OS. After modifying of files restart it by executing:

sh restart - it kills the service which starts automatically again sh restart_dbus-serial-battery - kills all instances of Serial Battery, reninstalls files and starts again If you restart the Serial Battery, wait until all instances are visible, assign CustomNames and restart the Aggregate Batteries

For debugging (to see the error messages in the console) it is reasonable to rename: ./service/run and start by: python3 aggregatebatteries.py

Logging file: aggregatebatteries.log

If you wish to mount the code into /opt/victronenergy/ follow these instructions: Dr-Gigavolt#24

Function:

On starts, the program searches for DBus services:

  • all Serial Batteries. Smart Shunts as battery monitor are neither supported nor needed, you can activate precise current measurement by Victron devices if the precision of your BMS is not sufficient.
  • one Smart Shunt for DC load (option)
  • Multiplus or Quattro (or cluster of them) for DC current measurement
  • all solar chargers (SmartSolar, BlueSolar, MPPT RS) for DC current measurement

The data from DBus are collected, processed and the results are sent back to DBus once per second. Dbus monitor defined in dbusmon.py is used instead of VeDbusItemImport which was very resources hungry (since V2.0). I strongly recommend to everyone modifying the code to keep this technique.

If you wish to combine the charger control parameters (CVL, CCL, DCL) provided by all instances of SerialBattery, please set OWN_CHARGE_PARAMETERS = False. If OWN_CHARGE_PARAMETERS = True, the charging and discharging is controlled by the AggregateBatteries.

In contrary to SerialBattery driver, I don't use the Bulk-Absorption-Float lead-acid-like algorithm. The LTO cells used by me are very robust and don't suffer at full charge voltage for longer period of time. Of course you shouldn't keep them above 2.5V, although max. voltage according datasheet is 2.8V. In case of constant voltage charging they are full at about 2.45V. But the most of you use LFP cells, therefore I added another approach since version 3.0. For LFP you have to set up the cell voltages according your experience or literature.

If the target charge voltage is set below the BALANCING_VOLTAGE (regular charging below 100% SoC), every BALANCING_REPETITION days full charge and balancing with BALANCING_VOLTAGE occurs. If not succesfull at given day (BALANCING_VOLTAGE not reached or cell voltage difference remains above CELL_DIFF_MAX), the next trial is done at the following day. The BALANCING_VOLTAGE is kept as long as the solar power is available. Then, when the cells are discharged from BALANCING_VOLTAGE down to CHARGE_VOLTAGE by own consumption, the process finishes. This algorithm avoids 100% charge during the most of the days in order to prolong the battery life. In contrary, the Bulk-Absorption-Float charges the battery to 100% every day, keeps the voltage for couple of minutes and then discharges the excessive charge into the grid. If you prefer it, just set OWN_CHARGE_PARAMETERS = False and use the calculation of the SerialBattery.

Changes in V3.1:

  • parameter BATTERY_EFFICIENCY, it is multiplied by charge fed into battery in order to minimize accumulation of SoC error if the batteries are not fully charged for longer period of time.
  • CHARGE_VOLTAGE_LIST containing a target cell voltage for each month.
  • KEEP_MAX_CVL parameter added, see explanation in settings.py

For better understanding whether the discharge to "Float" it useful or not please find and share some papers about LFP aging under constant voltage. Up to now I found such a document for LTO only (https://www.global.toshiba/content/dam/toshiba/ww/products-solutions/battery/scib/pdf/ToshibaRechargeableBattery-en.pdf or http://futuregrqd.cluster027.hosting.ovh.net/Download/Datasheet/Toshiba_LTO_2.4V_20Ah.pdf), see "Float characteristic".

If the battery is not balanced properly or the target voltage is set too high, one or more cell's voltages start to peak. To avoid emergency disconnecting of the battery by BMS, the dynamic CVL reduction is activated if at least one cell exceeds the MAX_CELL_VOLTAGE. To avoid instabilities of charger, the DC-coupled PV feed in (if initially enabled) will be disabled in order to enable the CCL. The CCL does not work if the DC-coupled PV feed-in is enabled, see: https://www.victronenergy.com.au/media/pg/Energy_Storage_System/en/configuration.html, chapter 4.3.4. When all cell voltages fall below MAX_CELL_VOLTAGE and the cell difference falls below CELL_DIFF_MAX, the DC-coupled PV feed in is enabled again (if was enabled before).

The charge or discharge current is set to zero if at least one BMS is blocking charge or discharge respectively. If charge is blocked, the DC-coupled PV feed-in (if initially enabled), will be disabled, see the reason above.