A Battery Energy Storage System (BESS) is a complete system that stores electricity in batteries and delivers it when needed. In EV charging, a BESS is used to increase effective site power, reduce operating costs, stabilize the load, and support smarter energy strategies such as peak shaving, power boosting, and the integration of renewables.
What Is a Battery Energy Storage System (BESS)?
A BESS is not just a battery pack. It combines hardware, power electronics, and control software to safely charge and discharge energy. A typical BESS includes:
– Battery modules/racks (energy storage)
– Battery Management System (BMS) for safety, balancing, and protection
– Power Conversion System (PCS/inverter) to convert and control AC/DC power
– Switchgear, protection devices, and isolation systems
– Thermal management (cooling/heating)
– Monitoring, communications, and cybersecurity controls
– Energy Management System (EMS) to optimize how and when the battery operates
BESS is usually specified using:
– Energy capacity (kWh or MWh)
– Power rating (kW or MW)
– Discharge duration (e.g., “500 kW for 2 hours”)
Why BESS Matters in EV Charging Infrastructure
EV charging demand can be high and uneven, while many sites have limited available import capacity or expensive grid upgrade timelines. A BESS improves feasibility and scalability by enabling:
– More chargers on the same grid connection
– Higher peak charging output without oversizing the utility connection
– Reduced peak demand and lower demand charges
– Smoother site load and fewer overload-related trips
– Higher self-consumption of solar PV and improved CO₂ performance
– Greater resilience and limited backup power operation when designed for it
For public hubs and fleet depots, BESS can shorten deployment time by reducing dependency on utility reinforcement.
How a BESS Works at an EV Charging Site
A BESS sits between the grid and the charging load, controlled by an EMS:
– The battery charges when grid capacity is available or electricity is cheaper
– The battery discharges when EV charging demand spikes or tariffs are high
– The EMS keeps the site within a maximum import limit
– Chargers may be coordinated with load management and power limits
Typical operating modes include:
– Peak shaving: discharge to cap site demand
– Power boosting: supplement the grid to increase charger output temporarily
– Load smoothing: reduce rapid load swings from multiple sessions
– Renewable shifting: store solar energy and use it later for charging
– Backup support: maintain essential loads during outages (site-specific)
Typical Use Cases
– Fleet depots with concentrated overnight charging demand
– Retail and commercial sites with strict maximum demand limits
– Public charging hubs where grid upgrades are slow or costly
– Sites with solar PV aiming to increase self-consumption
– Weak-grid or remote locations needing more stable power
Key Benefits of BESS
– Faster charging site rollout without immediate grid upgrades
– Lower operating costs through tariff optimization and peak management
– Higher effective charging capacity and better utilization
– Improved reliability through stabilized site power
– Better sustainability performance when paired with renewables
– Optional resilience capability for critical charging operations
Limitations to Consider
– Higher CAPEX and increased system complexity
– Battery degradation reduces capacity and power capability over time
– Requires correct sizing based on real charging profiles and business goals
– Safety, permitting, and fire protection requirements can add cost and lead time
– Round-trip efficiency losses mean not all stored energy is returned
– Not a full replacement for grid upgrades if continuous high power is needed long-term
Related Glossary Terms
Battery Buffer Storage
Energy Management System (EMS)
Battery Management System (BMS)
Available Import Capacity
Peak Shaving
Power Boosting
Smart Charging
Dynamic Load Balancing
Microgrid
Backup Power Operation