MaxCurrent logic with Custom charger

[ecfmau]

Hello, I created a setup where I can control my electric water heater and set its power to any one of 5 values:

• 0 kW
• 2 kW
• 3 kW
• 4 kW
• 6 kW

I did this with two Shelly switches which I can configure in order to dynamically "rewire" the water heater resistors. I wrote some logic in a PHP script, where I implemented the functions evcc can call for a Custom charger: status, enabled, enable and maxcurrent (according to this documentation).

Then I configured a Custom charger in evcc. I attached the relevant excerpt of my config.
evcc_solarboiler_yaml.txt

Now I'm confused with the way evcc calls enable and maxcurrent. When I set my heater/charger to 'minpv' or to 'now', evcc calls first maxcurrent(0) and then enable(1).

What does maxcurrent(0) mean in this context? In other words, which power value of my water heater am I supposed to set when I receive maxcurrent(0) from evcc? I see three possible interpretations:

1. Set the current to zero (in my case: set the power to 0 kW) and wait for evcc to make subsequent maxcurrent calls, which will gradually increase the current until we reach the surplus threshold
2. Set the smallest possible current (in my case: set the power to 2 kW) and wait for evcc to make subsequent maxcurrent calls, which will gradually increase the current until we reach the surplus threshold
3. Set no current limit, i.e. set the highest possible current (in my case: set the power to 6 kW) and wait for evcc to make subsequent maxcurrent calls, which will gradually decrease the current until we reach the surplus threshold

I did not find any information about this MaxCurrent logic in the documentation or in the discussions.

Thanks for your help and best regards,
Frederic

[ecfmau]

I found the answer to my own question. My config file for the maxcurrent URI parameter was wrong:
maxcurrent:
source: http
uri: "http://192.168.1.10:8077/evccboiler.php?maxcurrent={maxcurrent}"

The correct configuration is:
maxcurrent:
source: http
uri: "http://192.168.1.10:8077/evccboiler.php?maxcurrent={{.maxcurrent}}"

Now I receive maxcurrent(3) for mode 'minpv' and maxcurrent(10) for mode 'now' which is consistent with the min and max currents I set in the GUI.

I am leaving the discussion as a reference if it can help someone.

Cheers
Fred