Energy metering

Overview~

The firmware tracks power, session energy and per-phase voltage and current so it can show live figures, enforce the consumption and under-power limits, and report over Modbus and the API. How those figures are obtained depends on what sensing hardware the board has, selected by the energy meter mode.

Mode	Sensing used	Power is…
Dummy	none	calculated from the set charging current and a configured AC voltage
Current sensing	current transformers	calculated from measured current and a configured AC voltage
Current and voltage sensing	current transformers + voltage taps	the real product of measured current and measured voltage

A board can only use a mode its hardware supports: current sensing needs current transformers, and current-and-voltage sensing additionally needs the voltage inputs.

Modes in detail~

Dummy~

With no measurement hardware, the meter assumes the vehicle draws exactly the current the charger advertises as max, and multiplies it by a configured AC voltage value. This gives a reasonable energy estimate for limits and display on a minimal board, but it cannot see the vehicle's actual draw.

Current sensing~

Current transformers (CTs) on the supply conductors measure the real charging current. Power and energy are computed from that current and the configured AC voltage. Any CT with a 2000:1 ratio is suitable (for example DL-CT08CL5 or SCT-013-000). This tracks the vehicle's actual draw, while still assuming a fixed line voltage.

Current and voltage sensing~

With both CTs and voltage taps, the meter measures current and voltage together and reports true power. This is the most accurate mode and the one to use when the board has voltage sensing fitted.

Single and three phase~

Set the three phases option to match the installation. On a three-phase supply with three-phase sensing, all three phases are measured; on a single-phase supply only one is used. The reported per-phase voltages and currents reflect whichever phases are active.

AC voltage setting~

In the dummy and current-sensing modes there is no measured voltage, so a configured AC voltage value is used in the power calculation. In current-and-voltage mode this setting is not used because voltage is measured directly.

Configuration~

Current and voltage inputs are declared in board.yaml with their ADC channels and a scale factor, for example:

energyMeter:
  current:
    adcChannels: [4, 5, 6]
    scale: 0.090909091
  voltage:
    adcChannels: [7, 8, 9]
    scale: 0.47

The presence of these blocks determines which modes the board can offer. The mode itself, the three-phase flag and the AC voltage are runtime settings stored in NVS, adjustable in the Settings section of the web interface.

CAUTION

Working with high voltage is dangerous. Always follow local laws and regulations regarding high voltage work. If you are unsure about the rules in your country, consult a licensed electrician for more information.