My system currently consists of a Cerbo GX and a Multiplus-II 24|5000|120.
My target is to command the Cerbo GX via CAN bus to set the parameters for charge/discharge phases on a battery stack. The CAN communication works OK, I can see the right parameters on the VRM interface.
I’ve checked out the charge algorithm of the Multiplus-II device, and I decide to choos the fixed algorithm for simplicity. That’s what I understood:
In the first phase (BULK) the voltage limit should be the CVL parameter commanded via CAN bus (can anyone please confirm?) and the current should be constant. Where does this current value come from? In the tab charger of the VE Configure I see the parameter Charge current, is it related to the charging current for the BULK phase? One more thing: I tried to adjust the CCL parameter from the CAN bus but, at first glance, I’m not sure this is having any impact and I actually need to control the charging current.
After the BULK, the Multiplus-II goes in absorption and the current is reduced until reaching Absorption voltage, correct? Theoretically speaking, if I set the fixed algorithm, the float voltage shoudl be ignored, right?
Does anyone have experience about CAN comands for the parameters CVL, CCL, DCL?
One more question: as far as I’ve understood, it looks like it’s not possible to swicth between inverter/charger on the Multiplus-II via CAN bus. I guess the easiest way to do this is to disconnect the 230VAC from the multiplus-II AC input. Is this correct?
You cannot control the GX device over the CAN bus (as far as I’m aware - I don’t know if control can be done via the NMEA2000 interface).
You can control this over the Ethernet port, and various methods exist for this.
The CVL and CCL limits normally come from a connected BMS. - you don’t mention what type of battery system you are using.
The DVCC values are not related to the inverter’s voltage and current limit settings, but are capped by the inverter settings.
The inverter charges in constant current mode until the Voltage gets to the Absorption voltage, then the current starts to drop. Once the ‘Tail’ current drops to the set value, or a time expires (depending on charge mode) then the output Voltage is reduced to the Float value.
No you don’t control the inverter via CAN bus, The inverter can be controlled directly via a MK3/USB interface, or via the GX device using modbus commands or a node red script (or flow).
I didn’t set any battery type, basically I’m using a battery stack produced by my company and I’m doing the CAN BMS communication from a NI device to the Cerbo GX. I’m using the DVCC values for charge/discharge phases.
The point is the following: I thought that when charge starts, the charger should immediately set a constant current value (BULK phase) which should be the CCL parameter, let’s say 5A (this value is of course capped to the charge current parameter in the charger tab of Ve Configure, right?). In reality I see that the charger is not setting immediately 5A, but is increasing the current with a veeery slow ramp (about 5 minutes); the same thing is happening when I set CCL=0A. I guess this ramp comes form a safe approach to the charge phase in order to avoid a sudden increse/decrease of the charge current value at the start/stop of charging phase.
As far as you know is there any possibility to modify this ramp in some way, maybe adjusting some parameter on the Multiplus-II? I don’t know, may I could try to set a differente battery type or create a new battery type.
One more thing: does anyone have a detailed graph about the charge algorithm, which includes a precise description of the values (time, voltage, current) for each phase?
In the attached file you can find the settings of Multiplus-II, maybe I’m doing something wrong.