Battery energy storage systems (BESS) are integrated systems that store electricity in batteries and supply it back to a site when needed. In EV charging, BESS solutions help overcome limited available import capacity, reduce peak-demand costs, stabilize power, and support energy-optimization strategies such as peak shaving, power boosting, and renewable energy shifting.
What Are Battery Energy Storage Systems (BESS)?
A BESS is a complete engineered solution, not just a battery pack. It typically includes:
– Battery modules/racks (the energy storage)
– Battery Management System (BMS) for protection, balancing, and safety control
– Power Conversion System (PCS/inverter) to manage AC/DC conversion and power flow
– Switchgear, protection devices, and isolation equipment
– Thermal management (cooling/heating)
– Monitoring, communications, and cybersecurity controls
– Energy Management System (EMS) to optimize charging and discharging behavior
BESS deployments are usually defined by:
– Energy capacity (kWh/MWh)
– Power rating (kW/MW)
– Duration (e.g., “1 MW for 2 hours”)
Why BESS Matters in EV Charging Infrastructure
EV charging demand can be high, peaky, and time-dependent, while grid upgrades can be expensive or slow. BESS enables more flexible and scalable charging sites by:
– Supporting more chargers without immediately increasing grid connection size
– Lowering peak demand to reduce demand charges and avoid overload trips
– Stabilizing site load for improved reliability and power quality
– Increasing self-consumption of solar PV and reducing CO₂ footprint
– Enabling faster deployment where utilities cannot deliver upgrades quickly
– Providing limited backup power operation for critical charging use cases (when designed for it)
For fleets and public charging hubs, BESS can significantly improve uptime and economics.
How BESS Works With EV Charging Sites
A BESS is controlled to balance energy between the grid, on-site generation, and charging demand:
– The battery charges during low-demand periods or when electricity is cheaper
– The battery discharges when multiple EVs charge simultaneously or when tariffs are high
– The EMS caps site import to a defined limit and uses the battery to cover spikes
– Chargers can be coordinated with load management so site limits are respected
Common operating modes include:
– Peak shaving: discharge to keep site demand below a threshold
– Power boosting: supplement the grid to increase charging output temporarily
– Load smoothing: reduce sudden load swings as sessions start/stop
– Renewable shifting: store solar energy for later charging demand
– Resilience support: keep essential systems running during outages (site-specific)
Typical Use Cases
– Fleet depots with concentrated charging windows and limited grid capacity
– Retail and workplace sites with strict maximum demand limits
– Public charging hubs where high utilization creates demand peaks
– Sites with solar PV aiming to reduce energy costs and improve sustainability
– Remote or weak-grid locations needing more stable charging power
Key Benefits of BESS
– Higher effective charging capacity on constrained grid connections
– Lower operating costs through demand management and tariff optimization
– Faster rollout by reducing dependence on utility reinforcement timelines
– Improved site reliability and fewer overload-related shutdowns
– Better integration of renewables and improved sustainability reporting
– Optional resilience capability for priority charging loads
Limitations to Consider
– Higher upfront cost and added system complexity
– Battery degradation reduces capacity and power capability over time
– Correct sizing is critical; undersized systems provide limited value
– Safety, permitting, and fire protection requirements can be significant
– Round-trip efficiency losses add energy overhead
– Not a long-term substitute for grid upgrades if sustained high power is required continuously
Related Glossary Terms
Battery Energy Storage System (BESS)
Battery Buffer Storage
Energy Management System (EMS)
Battery Management System (BMS)
Available Import Capacity
Peak Shaving
Power Boosting
Smart Charging
Dynamic Load Balancing
Microgrid