Cell Voltage limitation - CVL

[wetty]

Please include system details:

Hardware:

• 2x Battery with 18x 280Ah connected in parallel to Multiplus II
• Venus on RPi 3B+
• 2x JK BMS connected to the Pi via dbus-serialbattery driver

Setup: DVCC Everything is off except BatteryAggregator as BMS

BatteryAggregator with the described behaviour was Version 3.2 (I have now updated to Version 3.13, but hat not tested again)

I checked the BatteryAggregator Settings after writing this issue and found that cvlMode is on max_always. But I thing non of the cvlMode does handle the scenario correct. I have to test a little bit further.

I have two scenarios for reducing the charge voltage.

• Switch to float voltage: One of the batteries is ready to switch to float, which means the voltage is normally reduced. The second battery is still loading, so overall voltage needs to be the charge voltage. In this case BatteryAggregator only reduces the voltage to the float value when both batteries are ready for the float mode. So it keeps the highest Charge Voltage of the two batteries. This works absolutly correct in BatteryAggregator. 😃
• Cell Voltage Limitation because overvoltage of one or more cells: SerialBattery has a CVL Function. This function prevents a bad balanced battery to overcharge the cell with the highest voltage and the bms to switch off because of overvoltage of this cell. In this case the overall charge voltage should be reduced to the minimum of the batteries. Here BatteryAggregator also stays at the highest voltage of the two batteries. Which I think is not correct.

Maybe it is a little bit tricky do decide which behaviour is correct. In my case when both batteries are in Bulk or Absorption mode then the minimum of the charging voltages is correct. When both batteries are in float mode, then the lowest voltage is correct. And when one batterie is in Bulk or Absorption and the other one is in float, then the voltage of the batterie in Bulk or Absorption should be correct.

[wetty]

Setting for CVL was "min_when_balancing". With this BatteryAggregator switches to the lowest value, which is in my example/Screenshoot the Foat/FloatTransition Value of Akku 1. Akku 2 is still balancing as the delta is 0.024V. So the overall Battery Charge Voltage should be the value of Akku 2. In my case 62.24V (18x 3.45 = 62.1V + 0.14V Drop Off).

So I thing the CVL Setting/Calculation needs something that ignores the Float and Float Transition mode as long as another Battery is still in Bulk or Absorption Mode. Then it should take the lowest value of all the Buld/Absorption Voltages.

Only when all Batteries are in Float Or Float Transition Mode the highest of the Float Voltages should be used.

[pulquero]

Can you check if the mode is available in dbus? This is the main issue with trying to implement CVL well, trying to extract the required information over dbus from the bms. Atm I am mainly dependent on /Io/AllowToCharge and /Balancing.

[wetty]

The Mode as string value is available under the battery Info/ChargeMode

Maybe have a look at the same problem from dbus-aggregate-batteries