Expand existing PV installation with battery storage via the Solis Smart Port

Many existing PV installations in the Benelux were installed without battery storage. When the existing solar panels and PV inverter are still functioning correctly, a full replacement is not necessary. With a suitable Solis S6 hybrid inverter, battery storage can be added to the existing installation via AC coupling, without the need to redesign the existing DC installation.

In this retrofit solution, the existing grid-tied PV inverter is retained. Its AC output is connected to the configurable GEN/Smart Port of the Solis hybrid inverter. The Solis then manages the battery, the energy flows and, when correctly configured, export to the public grid.^[1]

Why AC coupling?

AC coupling is the appropriate route when the existing PV installation must be retained. The battery is not connected to the existing PV inverter, but to the new Solis hybrid inverter.

• Preserve existing investment: The existing grid-tied PV inverter remains in operation.
• Add battery storage: The Solis hybrid inverter handles charging and discharging of the connected battery.
• Additional PV possible: New solar modules can be connected to the DC inputs of the Solis, provided all electrical values remain within the product specifications.
• Export control: With a correctly connected energy meter and the right settings, export limitation is configurable.
• Backup possible: Selected loads can be supplied via the backup output, within the power and installation limits of the chosen model.^[1][2]

The Solis Smart Port (GEN Port)

The Smart Port is a configurable AC connection, also referred to as the GEN Port in the official Solis documentation. Depending on the chosen configuration, the port supports three applications:^[1]

• AC Coupled: Connection of an existing grid-tied PV inverter.
• Generator: Connection of a supported generator.
• Smart Load: Switching or supplying a selected load.

System architecture

The existing PV inverter delivers its energy via the Smart Port to the AC system. The Solis manages the energy flows based on current power, operating mode, battery status and export settings. The generated energy can be used for:

• direct consumption by the connected loads;
• charging the battery via AC-to-DC conversion;
• export to the public grid, where permitted;
• supplying selected backup groups during island operation.

In addition to the AC-coupled installation, the Solis can process new PV strings via its own DC inputs, provided string voltages, input currents, MPPT ranges and other electrical values remain within the product specifications.^[1][2]

Energy metering: critical element

For correct charge, discharge and export control, the Solis must be able to accurately measure imported and exported power. A correctly positioned and configured energy meter is essential for this. Check during installation:

• position of the energy meter;
• measurement direction and phase sequence;
• communication connection and addressing;
• current import and export values;
• configured export limit.

Power control via Freq-Watt

When the public grid fails and the battery or loads cannot absorb all available solar energy, the output power of the AC-coupled PV inverter must be limited. Solis applies Freq-Watt control for this purpose: the hybrid inverter influences the frequency of the local AC grid, upon which a suitable PV inverter reduces its output power.^[1]

Before commissioning, verify the applicable grid code settings, the behaviour of the existing inverter at over-frequency, the firmware and the product-specific requirements.

Backup during grid outage

The Solis S6-EH3P(8-15)K02-NV-YD-L features a separate backup connection with a switching time of less than 10 milliseconds. The available continuous and peak power depends on the chosen inverter model.^[1][2]

When is this solution suitable?

AC coupling via the Solis Smart Port is the appropriate choice when:

• the existing PV inverter is in good technical condition;
• the existing solar panels and DC installation must be retained;
• battery storage, backup or export limitation is desired;
• additional solar panels will be added later via the Solis DC inputs;
• the existing PV inverter meets the requirements for the desired on-grid and any off-grid operation.

Technical considerations for installers

• Power of existing inverter: Verify the maximum permitted AC power and the model-specific limits of the GEN/Smart Port.
• Phase configuration: Verify whether the existing PV inverter is single-phase or three-phase and how power is distributed and measured across the phases.
• Energy meter: Verify position, measurement direction, phase sequence, addressing and communication.
• Export control: Activate export limitation only after meter readings and power direction have been verified.
• Battery compatibility: Verify the exact battery model, BMS version, communication, firmware and the correct battery selection in the Solis menu.
• Firmware: Verify before commissioning that the inverter and battery BMS meet the applicable manufacturer requirements.
• Protection: Dimension cables, overcurrent protection, earthing connections, disconnectors and surge protection in accordance with the installation manual and applicable installation standards.
• Backup groups: Select loads based on continuous power, peak power, battery power and desired autonomy duration.

Recommended inverter: Solis S6-EH3P(8-15)K02-NV-YD-L

For three-phase retrofit projects, the Solis S6-EH3P(8-15)K02-NV-YD-L is a suitable solution. This low-voltage series features a GEN/Smart Port, a separate backup output, connections for a compatible battery and DC inputs for solar panels.^[1][2]

The choice between the 8, 10, 12 and 15 kW versions is determined by:

• the power of the existing PV inverter;
• the existing and future PV power;
• the desired battery capacity and required charge/discharge power;
• the maximum simultaneous consumption and desired backup load;
• the grid connection and main protection.

Recommended battery: Dyness PowerBrick Plus 16.07 kWh

The Dyness PowerBrick Plus 16.07 kWh is a low-voltage battery listed in both the official Solis Battery Matching Compatibility List and the official Dyness Low-voltage Batteries Compatibility List.^[3][4] The actual usable capacity, charge and discharge power and the required number of batteries must always be matched to the consumption profile, desired backup duration and inverter specifications.

Smart Load and generator function

Depending on the configuration, the GEN/Smart Port can also be used for a generator or a Smart Load application. With Smart Load, a selected load, such as an electric heating element or other controllable load, is switched or supplied based on the available Solis settings. Always verify the permitted port power, load type, inrush currents and required protection.

Dynamic energy tariffs

The Solis Smart Port does not automatically switch off the existing PV inverter during negative energy prices. Price-dependent control requires a supported energy management system, external control or additional configuration. Present dynamic price control only as part of a concretely validated system solution.

Frequently asked questions

Can any existing PV inverter be connected to the Smart Port?

No. The connected power must remain within the electrical limits of the Solis. For production during island operation, the existing PV inverter must also be suitable and correctly configured for the applied frequency control.

Does the existing PV inverter need to be replaced?

Not when it is technically suitable for the chosen AC-coupled configuration and remains within the permitted power, phase and grid code requirements.

Can the battery be charged with energy from the existing PV installation?

Yes. The AC energy from the existing PV inverter can be used via the hybrid inverter to charge the battery, taking into account conversion losses, battery limits and the active system settings.

Can the existing PV installation continue producing during a grid outage?

This is possible under certain conditions. The existing PV inverter must be suitable and correctly configured for the local frequency control. In addition, the system must have sufficient battery or consumption capacity to absorb the generated energy.

Is zero-export possible?

Export limitation is possible when the system is correctly designed, the right energy meter is connected and the settings are configured in accordance with the Solis documentation.

Is the Dyness PowerBrick Plus officially compatible with the Solis S6-EH3P(8-15)K02-NV-YD-L?

The official Solis documentation lists the Dyness PowerBrick Series and the official Dyness documentation lists the Solis S6-EH3P(8-15)K02-NV-YD-L among the supported low-voltage inverters. The exact version, firmware, BMS and market-specific support must be verified separately before delivery.^[3][4]

What should I verify before installation in the UK or internationally?

Before offering and installing, verify that the exact Solis model and the applicable firmware or certificate version comply with the local grid code and the requirements of the relevant network operator. A datasheet or battery compatibility list alone is not proof of approval for a specific market.

Conclusion

With a suitable Solis S6 hybrid inverter and a correctly configured Smart Port, an existing PV installation can be extended with battery storage, export control and backup functionality, without the existing PV inverter needing to be replaced as standard. In combination with the Dyness PowerBrick Plus, a flexible low-voltage solution is created for retrofit projects. Careful verification of the existing PV system, power limits, meter position, grid code, battery configuration, communication, firmware and backup loads remains essential throughout.