Wallbox

The Wallbox function block is used to control a charging station for electric vehicles.

Charging a vehicle with the right power at the right time is essential for efficient energy management.

Therefore the function block comes with up to five customizable charging modes with which the charging power can be limited by individual logic.

With a dedicated input a charging session can be paused to avoid grid power peaks or equal.

Table of Contents

• Inputs
• Outputs
• Parameters
• Properties
• Charging session
• Minimum and maximum Limits
• Calculation of charging costs
• Programming example
• Authorization Sequence for Charging
• Detection of Invalid Meter Readings

Inputs↑

Outputs↑

Parameters↑

Properties↑

Charging session↑

A charging session is the time between connecting and disconnecting a vehicle. The session can be paused / resumed with inputs Ec, Ls or App.

Charge log on output Lcl is set when starting / ending a session or if the userID changes during an active session.

Minimum and maximum Limits↑

Minimum and maximum limits define the allowed range of Output Tp (Target charging Limit).

Charging Limit can be configured for each mode via Dialog/App, or via logic in Inputs Lm1-5.

If the charging limit falls below the minimum charging limit, charging is paused and target charging limit is set to 0.

The actual charging power is determined by the vehicle but will not exceed the maximum power settings.

Calculation of charging costs↑

The calculated costs of a charging session are provided at the Cclc output.
This is done via the energy consumed and it’s price per charging mode, and the connection fee per hour.

During a charging session, the current costs are output and continuously updated.
After the end of the session, the costs remain available at the output until the start of the next session.

Calculation:
kWh mode 1 * price mode 1 + kWh mode 2 * price mode 2 + (other modes) + duration of charging session * Cfp

The calculation is done on a rolling basis, meaning changes in modes and prices are considered from the moment of the change onward, not retroactively.

When managed by the Wallbox Manager, its prices are used instead.

By setting separate prices for energy and connection fees, users can tailor cost calculations to their preferences.
With enough Wallboxes, it makes sense to determine the costs primarily by energy prices.
In cases where the number of Wallboxes is limited, opting for a higher hourly connection fee (Cfp) helps prevent prolonged vehicle occupancy.

Programming example↑

In the properties window, you can define the number of entries in the history, the minimum and maximum charging power as well as a connection fee per hour:

Double click on the block to open the configuration window, here up to 5 charging modes can be created:

With additional logic at the input (Ec), charging is enabled when a user is successfully authenticated via the NFC Code Touch and the vehicle is connected.
An energy meter supplies the current charging power and meter reading to the function block.
The ID of the authenticated user is transferred at the "Uid" input.

Authorization Sequence for Charging↑

In commercial or communal installations where charging process authorization is necessary, the vehicle must be connected first, and only then can the charging be authorized via a pulse on Ec or Ecp (e.g., through NFC). If not, no charging will occur.
This sequence is critical because otherwise, an unauthorized vehicle could potentially charge at the expense of another.

In the programming example above, programming has been developed that allows for prior authorization. Following this, the charging process can be initiated for a limited time by connecting the vehicle.

In private households, the Ec input can often remain permanently active (negated) when unauthorized charging is not a concern. Under these circumstances, charging is generally permitted.

Detection of Invalid Meter Readings↑

The meter block detects invalid meter readings at the Mr input(s), which can occur due to faulty data transmission from a physical absolute value meter, and ignores them.

In general, only increasing or constant meter readings are allowed; decreasing or jumping to 0 readings are discarded.

Unrealistically high increases in meter readings are discarded if:
-The change in value is greater than the total previous consumption and greater than 10000.
-Only if the time difference since the last value change is less than 8 hours.