How to Trigger Force Discharge to Grid from Battery for Solax Inv.

Reed_Richards

Is it worth broadening the question to ask if anyone with any inverter has managed to achieve a forced discharge from a battery to the grid?  Anyone who has succeeded might provide a clue as to how it can be done whereas if nobody has done this it might imply that it is a feature that inverter manufacturers have not thought to provide.   

MWT

Reed_Richards said:

... if nobody has done this it might imply that it is a feature that inverter manufacturers have not thought to provide.   

A somewhat unhelpful answer I know, but yes, Tesla have that capability built into the Powerwall and they use it as part of their Virtual Power Plant (VPP) under the Tesla Energy Plan (TEP), but ... they do not expose that functionality to end-users.

Givenergy do have that capability I believe, see mode 4:

abeezar

I check with Solax, at present the ability to force discharge does not exist but they are working on an FW that does that. They did not have a time frame when it will be available. Also learned from another group Solax was developing a solution for Agile but no dates announced as of today.

Reed_Richards

I'm curious about the Tesla Energy Plan, a collaboration between Tesla and Octopus it seems.  The "75% savings on bills" sounds attractive but I presume that is a comparison with the bills without any battery.  Do you pay the same as some other Octopus tariff minus the standing charge whilst allowing Octopus to discharge your Powerwall battery if they feel like it?

MWT

Reed_Richards said:

Do you pay the same as some other Octopus tariff minus the standing charge whilst allowing Octopus to discharge your Powerwall battery if they feel like it?

No, there is more to it than that.

The tariff is balanced so you earn the same amount for export as you pay for import, the 0 SC covers round-trip losses for most people.

There are two tariffs, one for Tesla car owners at 8p/kWh and for non-Tesla owners 11p/kWh.

Tesla control the charging and discharging of the Powerwall down to a 30% reserve limit if your Powerwall supports the reserve feature.

Alan_R_

I have managed to discharge my solax battery to grid.  I programmed an Arduino Nano to reply to the inverter claiming incoming power of 5kw expecting the inverter to go to maximum output.  I have this set to address 3 and the normal meter on address 1.  I found it didn't work as expected but it did freeze the output at current power.  I guess the inverter makes small changes at a time to match the load and when it does not see a change it gets stuck.

I can discharge to grid by boiling a kettle for a few seconds to get full output and at this time change meter address from 1 to 3.  To change back to normal self use just switch back to 1.

I'll look into setting it up so it sits between the meter and inverter to add or subtract from the meter to charge from / discharge to grid with automatic control sometime.

Need a RS485 to TTL adapter for £3 on ebay as well.  My code below:

void setup() {

  Serial.begin(9600);

  while (!Serial) {

    ; // wait for serial port to connect

  }

  

}

void loop() {

  byte r;

  while (!Serial.available()) {}

  r = Serial.read();

  if (r == 0xb0) { //1st checksum in read command

    while (!Serial.available()) {}

    if (Serial.read() == 0x2a) { //2nd checksum in read command

      delay(10);

      Serial.write(0x03); // slave 3

      Serial.write(0x04); // function 4

      Serial.write(0x04); // sending 4 bits

      Serial.write(0x45); // IEE 754 5000w

      Serial.write(0x9c); //

      Serial.write(0x40); //

      Serial.write(0x00); //

      Serial.write(0x3c); // checksum

      Serial.write(0xa6); //

    }

  }

  if (r == 0xf4) { //test connectivity - 1st checksum in read command

    while (!Serial.available()) {}

    if (Serial.read() == 0x2a) { //2nd checksum in read command

      delay(10);

      Serial.write(0x03); // slave 3

      Serial.write(0x03); // function 3

      Serial.write(0x02); // sending 2 bits

      Serial.write(0x00); // register

      Serial.write(0xa8); // 

      Serial.write(0xc0); // checksum

      Serial.write(0x3a); //

    }

  }

}