ESS Design and Installation Manual - VE.Bus

A grid-connected energy storage system combines several Victron Energy products: an inverter/charger, a GX device, and a battery, usually together with solar. It stores energy, most often harvested from solar, and makes it available later, for example to power loads in the evening once solar production has stopped. The battery can also be charged from the grid, and a system can run without solar at all.

ESS is the Victron feature that makes those components work together as one. It coordinates the inverter/charger, the battery, the solar and the grid connection, deciding when to charge the battery, when to discharge it, and how much power to draw from or feed into the grid.

With ESS, the system can:

When the system has more power than the loads need and the battery is full, it can sell the surplus to the grid. When it cannot meet demand from the battery and solar alone, it draws the shortfall from the grid automatically.

ESS is configured in two places: the ESS Assistant, loaded into the inverter/charger with VEConfigure, and the ESS menu on the GX device. Both are described in Configuration.

Backup during a grid failure

When the utility grid fails, the inverter/charger disconnects from the grid and continues to power the loads on its AC output from the battery, and from solar when available. The loads are not interrupted. When the grid returns, the system reconnects and resumes normal operation without intervention.

How much of the battery capacity is held in reserve for a grid failure is set with Minimum SOC. The system respects that limit while the grid is present and ignores it during a failure, so the reserve remains available. Which loads stay powered depends on how they are wired, covered in System design.

PV: DC-coupled, AC-coupled, or both

The system can use solar in two ways. With DC-coupled PV, a SmartSolar or BlueSolar MPPT solar charger feeds the battery directly on the DC side. With AC-coupled PV, a grid-tie PV inverter feeds the AC side. A system can use either, or a mix of both. (How to choose is covered in System design.)

With or without a grid meter

The system can run with or without an external grid meter. With a meter, it can run alongside the grid as a full or partial grid-parallel installation. Without a meter, all loads, and any PV inverter, are connected to the AC output of the inverter/charger. (See System design.)

Generator backup

A generator can be used as backup during extended grid failures. The GX device can start and stop the generator automatically, ensure it is properly loaded, and shut it down once the battery is charged. Grid code and loss of mains (LOM) settings need particular attention in generator systems.

Feeding solar back to the grid

Surplus PV power can be exported to the grid where local regulations allow. Feed-in is possible regardless of how the PV is connected, whether it is DC-coupled, AC-coupled on the AC-In, or AC-coupled on the AC-Out.

Zero feed-in

With a supported grid-tie PV inverter, export to the grid can be prevented or capped at an agreed level. The system reduces the PV inverter's output as soon as export is detected. The supported PV inverters, and the settings each requires, are listed in Zero and limited feed-in with PV inverters.

Peak shaving

The power drawn from, or fed into, the grid can be capped at the grid connection point. When demand exceeds the limit, the battery supplies the difference, so the installation can support loads beyond the capacity of the grid connection and operate within a contracted or physically limited connection. See Peak shaving.

Scheduled charging

The battery can be charged from the grid during defined time windows, for off-peak tariffs, to prepare for a known outage, or to give the battery a regular maintenance charge. See Scheduled charge levels.

Dynamic ESS

Dynamic ESS optimises the system against a variable or dynamic energy tariff, scheduling battery charging and discharging to minimise energy costs while respecting the configured battery and grid limits.

Opportunity Loads

Surplus solar can be directed into flexible loads such as heat pumps, EV chargers, water heating and pool pumps, rather than being curtailed or exported. The power each load draws is configured, and the load is switched on once the available surplus is enough to cover it. Loads are served in a priority order, so the surplus is allocated to the most important load first.

EV charging

The Victron EV Charging Station connects to the GX device, where it is monitored and controlled alongside the rest of the system, both locally and through VRM. It can also be charged from surplus solar as an opportunity load.

Use ESS in a self-consumption system, a backup system with solar, or a combination of the two. What separates them is how much of the battery capacity is held in reserve for a grid failure. In a combined system, for example, 30% of the capacity is used for self-consumption and the remaining 70% held in reserve.

Self-consumption

When there is more PV power than the loads need, the surplus is stored in the battery. That stored energy is then used to power the loads when PV is insufficient.

The percentage of battery capacity used for self-consumption is configurable. Where utility grid failures are very rare, it can be set as high as the battery allows, making the full battery available for everyday use. Where grid failures are common, even a daily occurrence, a smaller share is used, for example 20% for self-consumption with the remaining 80% held in reserve for the next failure.

Backup

Where the battery is intended as backup rather than for daily cycling, it is held at a high state of charge and discharged only when the utility grid fails. Once the grid returns, it is recharged from the grid, or from solar when available.

The operating strategy that carries this out is selected with the Mode setting.

Do not use ESS in:

Inverter/charger

The core of the system is a MultiPlus or Quattro bidirectional inverter/charger. ESS can be installed only on VE.Bus models with the second-generation microprocessor (26 or 27); all VE.Bus inverter/chargers currently shipping have this.

GX device

A GX device manages the system and provides monitoring, both locally and remotely through the VRM Portal and the VRM app.

Battery

The system works with:

Battery monitor

In most systems a separate battery monitor is not needed:

A separate monitor is required only when a battery without an internal battery monitor (such as lead batteries) is combined with an additional power source, for example a DC wind generator. Where one is needed, use a SmartShunt, BMV-700, BMV-712, or Lynx Shunt VE.Can.

Grid meter (optional)

A grid meter is optional. It is installed in the main distribution board, between the grid and the installation, and is used in full or partial grid-parallel systems. A grid meter is needed only when AC loads or sources are present on the input side of the inverter/charger; when everything is on the output side, it is not required. (See System design.)

PV (optional)

The system can use grid-tie PV inverters, SmartSolar and BlueSolar MPPT solar chargers, or a mix of both. It can also run with no PV at all, which is typical of virtual power plants, where many small storage systems supply the grid at times of peak demand.

ESS requires at least:

Everything else, solar, a grid meter, additional inverter/chargers, is optional and added as the design requires. See System design.