The Role of DC Systems in Battery Energy Storage Systems

DC systems are a fundamental element of the architecture of Battery Energy Storage Systems (BESS). From managing the energy stored in batteries to ensuring the continuity of auxiliary systems, proper design of the DC section contributes to the reliability, safety, and performance of the entire energy storage system.

The battery energy storage market is experiencing very rapid growth. According to the International Energy Agency, 108 GW of new battery storage capacity were installed worldwide in 2025, approximately 40% more than in 2024. Around 80% of new installations were utility-scale projects.

As BESS installations continue to grow and their importance for grid flexibility increases, it is becoming increasingly important to properly design every element of the system, including the DC section.

What Is a Battery Energy Storage System?

A Battery Energy Storage System (BESS) is a system that stores electrical energy in batteries and makes it available when needed.

A BESS can be used, for example, to:

• store energy generated by photovoltaic or wind power plants;

• shift energy consumption over time;

• reduce peak demand;

• provide grid services;

• improve the stability and flexibility of the electrical grid;

• support the continuity of power supply to specific loads.

  
  

The IEA highlights the growing role of battery storage as a flexibility technology for the power system, with applications ranging from energy shifting to ancillary services and grid congestion management.

In a BESS, however, the battery is only one part of the overall architecture.

The system includes several subsystems that must operate in coordination: batteries, Battery Management System (BMS), power conversion systems, protection systems, control, monitoring, and auxiliary systems.

It is precisely in this context that the DC system plays a central role.

Why Is DC Power So Important in BESS?

Batteries store and deliver energy in direct current (DC).

The energy must then be converted so that it can be supplied to the AC electrical grid or, conversely, so that the batteries can be charged from an AC power source.

The connection between the DC battery side and the AC grid is normally managed through a power conversion system, such as a Power Conversion System (PCS).

In simplified terms:

AC Grid → PCS → DC System → Batteries

during charging;

Batteries → DC System → PCS → AC Grid

during discharging.

The DC system is therefore a fundamental part of the BESS energy path. However, its role goes beyond simply connecting the batteries.

What Are the Main Components of a DC System for BESS?

The configuration may vary depending on the project architecture, battery technology, installed power, and application requirements.

The main components may include:

Batteries

They are the heart of the energy storage system and represent the DC energy source.

Lithium-ion technology is currently the most widely used technology in new battery storage systems, with LFP (lithium iron phosphate) cells accounting for approximately 90% of new installations in 2025, according to the IEA.

Battery Management System

The BMS monitors and manages key battery parameters, contributing to battery protection and operational control.

Monitored parameters may include voltage, temperature, state of charge, and other indicators required for effective battery management.

DC Protection and Switching

The DC section must include appropriate protection, isolation, switching, and circuit management systems.

The design must take into account the specific characteristics of DC power, operating voltages, and expected short-circuit currents.

Power Conversion System

The PCS manages the conversion between AC and DC.

It is one of the key elements enabling the BESS to interact with the electrical grid.

DC Auxiliary Systems

In addition to the main energy path, a BESS may require dedicated DC power supplies for control, protection, communication, and other auxiliary functions.

This is where the reliability of the DC solution becomes particularly important.

Power DC System and Auxiliary DC System: Two Different Functions

It is important to distinguish the BESS power DC path from DC systems dedicated to auxiliary loads.

The first is directly involved in the transfer of energy between the batteries and the PCS.

The second can supply devices and systems that must remain operational to enable the control and management of the plant.

In a mission-critical application, the loss of auxiliary power can compromise the operation of control, protection, communication, or supervision systems, even when energy is still available in the batteries.

For this reason, the auxiliary DC system must be designed considering not only the required power, but also:

• autonomy;

• redundancy;

• service continuity;

• alarm management;

• monitoring;

• environmental conditions;

• maintenance;

• project-specific requirements.

  
  

The Role of Industrial Rectifiers and Battery Chargers

In an industrial DC system, the rectifier/battery charger performs an essential function: it converts the available AC input power into DC and contributes to maintaining the battery state of charge and supplying the DC loads defined by the system architecture.

The rectification system must be selected according to the requirements of the application.

Key parameters to consider include:

• nominal DC voltage;

• available current;

• battery capacity;

• required autonomy;

• load characteristics;

• operating conditions;

• redundant configuration;

• monitoring and communication requirements.

  
  

For industrial applications and mission-critical infrastructures, design therefore cannot be limited to the selection of a single component: the DC system must be considered as a whole.

Battery Monitoring: Why Is It Essential?

BESS reliability also depends on the ability to monitor the operating conditions of the batteries in real time.

Monitoring parameters such as voltage, current, and temperature makes it possible to identify abnormal conditions and support more effective system management.

A battery monitoring system can help to:

• identify anomalies;

• monitor changes in battery condition;

• support maintenance activities;

• improve system availability;

• increase visibility into battery performance.

  
  

LEVER develops industrial battery monitoring systems capable of monitoring voltage, current, and temperature in real time, with anomaly detection and alarm functions.

In a BESS, this monitoring capability is particularly important because the battery is not simply an energy reserve: it is a strategic component of the entire system.

Reliability: The DC System Must Be Designed for the Application

There is no single DC architecture that is suitable for every BESS.

A system designed for a commercial photovoltaic plant has different requirements from a utility-scale system connected to the grid or a mission-critical industrial application.

The design must therefore consider at least:

Power and Voltage

What are the operating voltage levels and currents?

Autonomy

For how long must auxiliary loads remain powered in the event of a loss of the primary power source?

Redundancy

Which components need to be redundant to ensure service continuity?

Environment

Will the system be installed indoors, outdoors, in high-temperature environments, or under particularly demanding operating conditions?

Monitoring

Which parameters need to be measured and which alarms need to be available?

Communication

Which interfaces need to be integrated with the BMS, SCADA, and supervisory systems?

Maintenance

How should inspections, replacements, and maintenance activities be managed?

These aspects should be defined during the early stages of the project.

BESS and Mission-Critical Infrastructure

The growth of battery storage is also increasing the variety of applications.

BESS are used to integrate renewable energy sources, increase grid flexibility, and manage energy over time. In 2025, energy shifting became the leading application for new battery storage projects, accounting for more than 90% of new projects according to the IEA.

However, these systems should not be evaluated solely on the energy capacity of their batteries.

A BESS is a complex system in which power conversion, control, protection, communication, and auxiliary power supplies must operate in coordination.

The quality of the DC architecture can therefore have a direct impact on the overall reliability of the plant.

The Value of a Custom-Designed DC Solution

For industrial applications and complex infrastructures, the most effective solution is not necessarily a standard one.

A BESS project may require customized specifications relating to:

• voltages and currents;

• DC system configuration;

• redundancy;

• communication interfaces;

• alarms;

• battery monitoring;

• environmental conditions;

• technical documentation;

• testing and commissioning procedures.

  
  

LEVER specializes in the design of static power conversion systems and provides BESS solutions together with industrial rectifiers, DC/AC inverters, and battery monitoring systems. The company also offers the possibility of customizing alarms and communication interfaces according to the project's technical specifications.

This approach makes it possible to consider the DC system not as an isolated component, but as an integral part of the BESS energy architecture.

Conclusions

Battery Energy Storage Systems are playing an increasingly important role in modern power systems.

The growth of utility-scale installations and the increasing number of applications related to renewable energy integration and energy shifting make it increasingly important to design reliable and flexible BESS solutions.

Within this architecture, the DC system represents a strategic element.

It is not simply the connection between the batteries and the power conversion system: the DC section also includes power supply, protection, control, and monitoring functions that can be critical to the operational continuity of the plant.

The proper design of rectifiers, DC systems, inverters, batteries, and monitoring systems makes it possible to develop an architecture that is consistent with the application's requirements and the project's reliability objectives.

LEVER provides expertise in static power conversion and the development of industrial solutions for BESS applications, with systems that can be customized according to specific project requirements.

Do you have a BESS project and need to define the DC system architecture?

Contact the LEVER team to evaluate the solution best suited to your application.