Can someone explain these Sofar settings?

[cajocars]

I have a Sofar ME3000SP which I’ve so far (no pun intended) used in lithium mode with communication to the Seplos BMS.

I’m trying to use it in general mode (intended for lead-acid batteries) and it has these parameters

Overvoltage protection (V)
Max charge voltage (V)
Low voltage protection (V)
Min discharge (V)
Empty discharged (V)
Full charged (V)

This is what I understand so tell me if I’m right or wrong:

I guess the last 2 are used to estimate the SoC

Max charge voltage is the voltage not to be exceeded during charge; I assume this is first limited by the amount of current the battery can take and as the voltage hits this limit the current is reduce (constant current- constant voltage charging). Is this right?

Overvoltage protection: I don’t see the point if the above is correct

 

[MaikaiLifeDIY]

Overvoltage protection (V)
Max charge voltage (V)
Low voltage protection (V)
Min discharge (V)
Empty discharged (V)
Full charged (V)

I'll give it my best shot.


Overvoltage protection (V) - This would typically be when the system shuts down or limits any further charging for safety reasons.
Max charge voltage (V) - This is the maximum voltage while charging, aka the "Bulk/Absorption" voltage.
Low voltage protection (V) This is the same as the over-voltage, when the system should shut down or limit further discharge.
Min discharge (V) - This would probably be the floor you want to discharge down to, for example, if you only wanted to discharge to 30% then whatever voltage gets you to that value is what would go here.
Empty discharged (V) - This is the voltage that would indicate the battery is dead and should probably be above the "Low voltage protection"
Full charged (V) - This is the resting voltage that would indicate the battery is full, probably the "Float" voltage.

 

[cajocars]

So I tried with


Overvoltage protection (V) 55.8
Max charge voltage (V) 55.5
Low voltage protection (V) 44
Min discharge (V) 46
Empty discharged (V) 46.7
Full charged (V) 56.9

The bms settings are
High voltage alarm 55.5
High voltage protection 56
Monomer high voltage alarm 3.4
Monomer overvoltage protection 3.65

The charge seems to have stopped at 55.11V (bms was showing SoC 95%, but inverter SoC was 100%)

 

[SeaGal]

I’m trying to use it in general mode (intended for lead-acid batteries) and it has these parameters

Why? Surely better to use it as it was intended and le the BMS tell the SoFar the SOC?

So I tried with

Overvoltage protection (V) 55.8
Max charge voltage (V) 55.5
Low voltage protection (V) 44
Min discharge (V) 46
Empty discharged (V) 46.7
Full charged (V) 56.9

The bms settings are
High voltage alarm 55.5
High voltage protection 56
Monomer high voltage alarm 3.4
Monomer overvoltage protection 3.65

The charge seems to have stopped at 55.11V (bms was showing SoC 95%, but inverter SoC was 100%)

That makes perfect sense to me.

You have set the inverters Max charge voltage to 55.5V, so by the time the battery gets to 55.11V and you likely have 390mV of voltage drop across your wire and connections between inverter and battery, the inverter's output voltage has reached 55.5V and charging stops. And that's assuming both BMS and inverter are measuring voltages to that accuracy in the first place.

I also see no reason why you have set the inverters 'full charged' detection voltage higher than its 'max charge voltage'.

 

[cajocars]

Why? Surely better to use it as it was intended and le the BMS tell the SoFar the SOC?


That makes perfect sense to me.

You have set the inverters Max charge voltage to 55.5V, so by the time the battery gets to 55.11V and you likely have 390mV of voltage drop across your wire and connections between inverter and battery, the inverter's output voltage has reached 55.5V and charging stops. And that's assuming both BMS and inverter are measuring voltages to that accuracy in the first place.

I also see no reason why you have set the inverters 'full charged' detection voltage higher than its 'max charge voltage'.

I’m trying to avoid communication between bms and inverter because the inverter takes the bms’ SoC value without decimal places so 99.5% becomes 100%. So my battery always charges to 99.5%, not 100%

The bms used to keep the SoC to 98% (flatline at that value while charging) and not increase to 100% until certain conditions were met (hitting an overvoltage protection); I don’t see this behaviour anymore and don’t know how to get it back (it’s likely a combination of the cell/total overvoltage alarm/protection)

I also thought about the voltage drop between bms and inverter, but I would expect it to stop charging when the ‘full charged’ voltage is reached, not the ‘max charge’; I thought ‘max charge’ was the constant voltage charge threshold ; I set the ‘full charged’ voltage higher than ‘charge max’ because I wanted to avoid it hitting 100% and stop charging, I want the bms to do that

 

[SeaGal]

IMHO it is better to use the SOC and the inverter to control the charge / discharge rate. Without comms between battery and inverter, the battery looses it's ability to demand different charge rates depending on SOC and temperature. And voltage is not a good measure of SOC, especially when there is charge or discharge happening.

I also prefer the BMS to be there as a fail-safe to cut off dangerous conditions, rather than the primary means of stopping charge, but YMMV.