Wallbox Pulsar Plus: kWh counting error - Diagnosis

⚠️ SAFETY WARNING / ELECTRICAL RISK. This appliance operates with dangerous mains voltages (230V single-phase or 400V three-phase). Any physical intervention inside the device or on the power distribution board carries a serious risk of electric shock. Before performing any physical check, it is mandatory to isolate the system by switching off the dedicated miniature circuit breaker/residual current device in the general electrical panel and verify the absence of voltage with a suitable instrument. It is strongly recommended to entrust any wiring or internal diagnostic operation to a qualified technician. ReeFix provides this diagnosis EXCLUSIVELY for educational and informational purposes.

CHECK 1: Connection Stability and Data Synchronization

Probability: 55%

This is the most common issue. The Wallbox Pulsar Plus stores charging session data locally before sending it to the myWallbox cloud via Wi-Fi or Bluetooth. If the connection is unstable or absent, data is not synchronized and may appear partial or missing in the app.

Key signals:

• Charging sessions that show zero kWh in the myWallbox app or do not appear in the history at all.
• Data updates or appears partially after keeping the smartphone connected to the Wallbox via Bluetooth for several minutes.
• Often occurs in installations where the Wi-Fi signal is weak (e.g., Wallbox far from the router).

Quick checks (user):

1. Forced Restart: Completely power off the Wallbox using the dedicated circuit breaker in the electrical panel. Wait 5 minutes to allow capacitors to discharge, then power it back on. This can reset the internal memory buffer.
2. Bluetooth Synchronization: Ensure your smartphone is close to the Wallbox. Temporarily disable phone Wi-Fi to force a Bluetooth connection. Open the myWallbox app and leave it active for at least 5-10 minutes to allow a full synchronization of the local buffer with the cloud.
3. Wi-Fi Signal Strength: Check the Wi-Fi signal strength (RSSI) received by the Wallbox. A value worse than -75 dBm (closer to -80 or -90 dBm) is critical and causes frequent disconnections. You can check this via the advanced settings of the Wallbox app or a Wi-Fi analysis app on your smartphone placed near the charger.

Preliminary decision: If after restarting and Bluetooth synchronization the data still does not appear or is still partial, there might be a deeper connectivity or firmware issue.

CHECK 2: Modbus Bus Integrity (if Power Boost is present)

Probability: 25%

If your Wallbox is configured with the Power Boost function, it uses an external energy meter (Power Meter) connected via an RS485 serial bus (Modbus RTU protocol). Wiring problems or interference on this bus can corrupt consumption data, affecting kWh counting.

Key signals:

• Counting errors (underestimation or overestimation) occur mainly when dynamic load management (Power Boost) is active or in the presence of strong concomitant household electrical loads.
• The problem does not occur if the Power Boost function is deactivated or if the Wallbox charges without load management.

Checks (requires technician):

1. RS485 Wiring Inspection: A technician should verify that the RS485 Modbus Shielded Network Cable is shielded and twisted pair, and that the shield is correctly grounded on only one side to prevent ground loops and interference.
2. Termination Resistor: If the bus length exceeds a few meters, the presence of a 120 Ohm termination resistor between the A- and B+ terminals at the end of the line is essential. Its absence can cause signal reflections and data corruption.
3. Meter Diagnostics: The technician can test the Carlo Gavazzi EM112 Modbus Energy Meter to verify its correct operation and the absence of communication errors.

Preliminary decision: This cause requires the intervention of a specialized technician. Do not attempt wiring or meter checks if you are not qualified.

CHECK 3: Internal Measurement Circuit and Power Supply Diagnostics

Probability: 20% (15% hardware + 5% power supply)

This category includes more serious hardware problems within the Wallbox itself, such as a defect in the energy measurement circuit or anomalies in the electrical power supply that can falsify readings.

Key signals:

• Constant and linear underestimation of kWh delivered compared to what is indicated by the electric vehicle's onboard computer or a reference energy meter, regardless of Wi-Fi/Bluetooth connection.
• Random counting errors associated with voltage surges or micro-interruptions on the local electrical grid.
• A real micro-case: In some cases, a filter capacitor on the logic board, degraded by heat, caused unstable current readings and a 10-15% undercounting.

Checks (requires qualified technician):

1. Current and Voltage Measurement: With an active charging session, a technician will use a HT Instruments True RMS Clamp Meter to compare the actual current drawn by the vehicle with the instantaneous value shown in the myWallbox app. Simultaneously, a Fluke 179 Professional Digital Multimeter will verify the stability of the input power supply voltage. Voltage drops greater than 4% under load can affect the calculation.
2. Internal Visual Inspection: A qualified technician will open the Wallbox to inspect the internal logic board for signs of overheating, oxidation on current transformer pins, or bulging electrolytic capacitors.
3. Firmware Update: Verify that the Wallbox is running the latest stable firmware version. Outdated firmware may contain known bugs related to measurement or synchronization.

Preliminary decision: Any intervention on internal components or direct measurement requires a specialized technician. Repair costs for internal boards can be high, and often the replacement of the entire unit is considered.

CONCLUSION

Based on probability and complexity of interventions:

1. If data does not appear or is partial (55%): Perform the Quick Checks in Section 1 (restart and Bluetooth synchronization). If the problem persists, check the Wi-Fi signal strength. If the signal is weak or unstable, try to improve coverage (e.g., with a Wi-Fi repeater) or contact a technician for a network evaluation.
2. If counting is incorrect with Power Boost active (25%): Contact a specialized technician for an in-depth diagnosis of the Modbus wiring and external energy meter, as described in Section 2.
3. If counting is consistently incorrect and not related to connectivity (20%): It is very likely an internal hardware failure or a power supply issue. In this case, it is essential to contact a qualified technician for the instrumental checks in Section 3.

Operational decision: If user checks do not resolve the problem or if symptoms indicate a hardware or Modbus fault, contact a qualified technician. Repairing internal components is complex and expensive; in case of a serious logic board failure, device replacement might be the most cost-effective option.

If the Carlo Gavazzi EM112 display does not communicate with the wallbox, immediately check that the Modbus address is set to 1 and that the baud rate exactly matches the parameters required by the charger.