Home PV system in Momino village

With a charging station for Tesla

Roman Rubanovich, NENCOM

Every day we receive inquiries about building photovoltaic (PV) systems and send commercial offers. Unfortunately, our prices are higher than the market average, and there is nothing we can do about it; high-quality components and skilled labor are not cheap at all.

Of course, clients for whom the selection criterion is only the lowest price decline our offers. However, we do not get upset because there are enough customers who prefer to delve into the details before paying.

«I compared several offers from different companies, and I won’t hide it, the solution from NENCOM turned out to be the most expensive. At the same time, I like your attitude toward work, and I see that high-quality equipment is included in the specification, so I agree» — the owner of a cozy rural house from the Targovishte municipality told us over the phone.

As usual, we first developed a 3D model of the system with exact dimensions and coordinated it with the customer. After that, we fully assembled in our workshop the part of the equipment that is to be installed in the technical room.

At the next stage, we launched the system, updated the firmware of its components to the latest versions, set up the configuration, and performed the necessary tests. This approach allows us to significantly reduce the duration of installation work on-site and improve its quality.

We installed 36 solar modules SHARP NUJC 440 on the roof of the house, with a total peak power of 15.84 kWp, arranged across six slopes with different inclinations and azimuths. Each such group requires individual maximum power point tracking (MPPT).

Simulation of PV module shading

The distinctive feature of SHARP NUJC series PV modules is that they are certified according to the Swiss regulation for hail resistance with a diameter of up to 40 mm (standard — up to 25 mm).

Four small groups (a total of 17 modules) were connected to four solar charge controllers by Victron Energy, which step down the voltage from the PV panels to the level required for battery charging.

To store excess solar energy, we installed a lithium iron phosphate BYD battery LVS with a capacity of 20 kW·h, consisting of five modules of 4 kW·h each.

The central component of the system is the Victron MultiPlus-II battery inverter with a power of 10 kV·A (around 8 kW), featuring an integrated charger. Its main task is to convert the direct current (DC) from the battery and charge controllers into alternating current (AC) at 230 V.

The tiny chair was kindly provided by the client

Victron inverters are known for their multifunctionality. Unlike most inexpensive inverters, they can mix energy from photovoltaic modules, battery storage, and the grid (or generator) at the input to provide the required output power.

In the event of an emergency grid shutdown, the inverter switches to standalone mode within 20 milliseconds to ensure uninterrupted power supply to the house. Since the MultiPlus-II is a bidirectional inverter, it can also charge the battery from the grid if necessary.

We connected two large groups of PV modules (a total of 19) to the on-grid inverter Hypontech HPS 6K. Typically, «grid-tie» or «on-grid» inverters cannot operate without the utility grid, which is why they are called that, but in our case, the HPS 6K will work even autonomously, as its microgrid is created by the Victron battery inverter.

The integration of the Hypontech on-grid inverter into the Victron hybrid or off-grid system requires specific settings but ensures high efficiency and reliability of the system as a whole.

All the listed devices are connected to the «brain» of the power station — the communication center Cerbo GX from Victron. Cerbo ensures coordinated operation of all components, offers exceptional settings and control options, and transmits detailed data to the Victron portal (VRM) for storage and remote monitoring.

Additionally, we connected the GX Touch Display with a 5-inch diagonal, which allows local control of the system.

In this animation, recorded on November 20, 2024, at 12:30 PM, we see that the Hypontech PV inverter fully covers the current consumption in the house, and the excess generation is directed to the battery through the Victron inverter. All power from the Victron charge controllers also goes into the battery.

Touch Display Victron 20.11.2024

In the device list, we can check the current power of each controller individually, and by entering the specific device’s menu, all technical details about its operation will be visible.

Accessing the display is also possible through the remote console on the VRM portal if the user has the appropriate permissions. Additionally, any authorized user of the specific system can monitor its operation on the homepage:

Dashboard Victron Energy 20.11.2024

At the requirement of the grid operator, we also installed external «Anti-Islanding» protection to prevent the inverters from feeding voltage into the utility grid during its disconnection, which could be dangerous for emergency crews. Technically, this was unnecessary, as the Victron Energy MultiPlus-II and Hypontech HPS inverters have built-in «Anti-Islanding» protection, as confirmed by the relevant certifications.

For the Tesla Model 3, we mounted the Victron charging station. It can charge the battery of the electric car not only at a fixed speed but adaptively as well.

In the second case, the station’s power is automatically adjusted based on solar generation and other loads in the house. This allows the use of only free energy for charging and also prevents overloading the battery inverter in off-grid mode.

The charging process can be monitored through the Tesla or Victron Energy apps on the phone, as well as on the charging station display or on the large screen inside the electric vehicle.

The Victron charging station can deliver up to 32 A in a 1-phase or 3-phase system, providing 7.3 or 22 kW of power, respectively. The built-in AC-DC converter in the Tesla Model 3 can accept up to 32 A from a single phase (7.3 kW) and up to 16 A from three phases (11 kW).

In addition, Tesla allows setting the maximum charging current for different locations, taking into account the capabilities of the electrical grid at the specific site.

The solar power plant is working well, significantly reducing electricity bills, charging the electric vehicle, and providing uninterrupted power to the home. The customer is satisfied with the result and plans to install a second battery to increase autonomy.

The cost of this hybrid system in September 2024 was 54 870 lv (28 055 €) including design, delivery, installation, commissioning, and VAT.