Charging voltage change from absorption voltage to rest voltage

[RRonGit]

Hello everyone,

I have the following environment:

Raspi4 with VenusOS Verion v3.30 2x Seplos battery packs --> BMS Seplos BMS V16 (10E) Software version: 16.6 venus-os_dbus-serialbattery installed by mr-manuel Version: 1.2.20240409dev BatteryAggregator installed via Setup Helper Version: v3.0.50

The BatteryAggregator aggregates the two batteries well so far.

Settings of venus-os_dbus-serialbattery:

In the config.ini of venus-os_dbus-serialbattery "Charge Voltage limitation (affecting CVL)" is enabled:

CVCM_ENABLE = True

This causes the battery to charge up to MAX_CELL_VOLTAGE (can seen as absorption voltage).

Then under certain circumstances the charging voltage changes to FLOAT_CELL_VOLTAGE (can be seen as resting voltage).

The problem:

If the first battery changes to FLOAT_CELL_VOLTAGE, but the second battery is still at MAX_CELL_VOLTAGE (because it still wants to do balancing), the BatteryAggregator sets the charging voltage equal to FLOAT_CELL_VOLTAGE.

The second battery cannot then complete the balancing.

It would be better if the BatteryAggregator only switches to FLOAT_CELL_VOLTAGE when both batteries switch to FLOAT_CELL_VOLTAGE.

Is this setting possible with the BatteryAggregator?

[pulquero]

The current behaviour is: If the aggregated /Balancing is 1, the max of the voltages is used, else the min. The aggregated /Balancing is the max of the individual /Balancing. So assuming MAX_CELL_VOLTAGE implies /Balancing is 1 then this should work.

Can you verify the behaviour of the individual battery /Balancing?

On the aggregator, you can also set /LogLevel to INFO to see what is happening in practice (please attach any log).

[RRonGit]

I noticed the following: one of the two batteries was balancing the cells. The other one doesn't. In VenusOS I see that the battery that is being balanced has "Allow to balance" set to none.

Is this "Allow to balance" value the trigger for the BatteryAggregator to switch between the absorption voltage and the resting voltage?

[pulquero]

No, /Io/AllowToBalance is different from /Balancing. To confirm, are you saying it is 'no' when it is balancing or 'no' when it is not balancing? You should use dbus-spy to check /Balancing.

[RRonGit]

When the battery is balanced, dbus-spy will display 0. I think that venus-os_dbus-serialbattery cannot read the balance status from the battery.

Status: com.victronenergy.battery.ttyUSB0 SerialBattery(Seplos)

Status: com.victronenergy.battery.aggregator Battery Aggregator

Could that be the problem?

[Albarge]

I'm not sure I understand how the logic works exactly, but if any battery is still balancing and a different one switches to float early, the best solution is to increase the pre set MAX_VOLTAGE_TIME_SEC = 900 (15 minutes) to allow all the batteries to balance for longer.

Otherwise MAX_CELL_VOLTAGE cannot be adjusted (limited lower) by the CVL functions which are arguably more important for cell protection, and a really useful function of sbattery: https://github.com/pulquero/BatteryAggregator/issues/45#issue-2251852273

[RRonGit]

That increases the parameter MAX_VOLTAGE_TIME_SEC is a good idea and I've tried it now. Unfortunately, after reaching MAX_CELL_VOLTAGE (sbattery charge mode LINEAR_LIMITATION_ENABLE = True) it switches to float immediately and not after the time set in MAX_VOLTAGE_TIME_SEC. So that's not a solution either.

[Albarge]

This is probably a Serial Battery settings issue. Maybe this thread is useful to read and make some adjustments to your settings to make it work:

https://github.com/Louisvdw/dbus-serialbattery/discussions/1036#discussion-6510569

*Edit: Also, if you don't go below SOC_LEVEL_TO_RESET_VOLTAGE_LIMIT = 80 overnight (Between charge cycles) or reboot when SOC is also still above that, then it will go straight to float too, maybe if that's the case try a higher reset SOC to re-trigger.

Or ask on the Serial Battery Github if it's still not working

[RRonGit]

Now it's working. I adjusted the following settings in sbatterie config.ini:

; --------- Charge mode --------- LINEAR_LIMITATION_ENABLE = True

; --------- Charge Voltage limitation (affecting CVL) --------- CVCM_ENABLE = True

; -- CVL reset based on cell voltage diff (linear mode) MAX_VOLTAGE_TIME_SEC = 3600

; --------- Voltage drop --------- VOLTAGE_DROP = 0.050

Thank you very much for the help/support.