Battery energy storage (BESS) is a system that stores electricity in batteries and delivers it back to a site when needed. In EV charging, a BESS is used to increase effective site capacity, reduce electricity costs, improve power stability, and support smart energy strategies such as peak shaving, power boosting, and renewables integration.
What Is Battery Energy Storage (BESS)?
A BESS is more than just a battery pack. It is a complete engineered system that typically includes:
– Battery modules and racks (the energy storage)
– Battery management system (BMS) for safety and control
– Power conversion system (PCS/inverter) to charge/discharge and manage AC/DC power
– Protection devices, switchgear, and safety systems
– Thermal management (cooling/heating)
– Monitoring, communications, and control software
– An energy management system (EMS) to optimize operation based on site goals
BESS capacity is usually described by:
– Energy (kWh or MWh)
– Power (kW or MW)
– Discharge duration (e.g., “500 kW for 1 hour”)
Why BESS Matters in EV Infrastructure
EV charging adds high and variable electrical demand. Many sites are limited by available import capacity or face high demand charges. BESS improves the business case and scalability of charging sites by enabling:
– More chargers or higher power without immediate grid upgrades
– Lower peak demand and reduced demand charges
– Smoother site load and improved electrical stability
– Better utilization by supporting simultaneous charging sessions
– Increased self-consumption of on-site renewables (solar PV)
– Improved resilience, including limited backup power operation when designed for it
For public hubs and fleet depots, BESS can reduce time-to-deployment by avoiding long utility upgrade timelines.
How BESS Works With EV Charging
In a charging site, BESS is typically controlled to balance three sources and demands:
– Grid import (limited by contracted capacity or switchgear)
– Renewable generation (solar PV, sometimes wind)
– EV charging load (variable and often peaky)
Common operating modes include:
– Peak shaving: discharge to keep site import below a threshold
– Power boosting: supplement the grid so chargers can deliver higher power temporarily
– Load smoothing: reduce rapid demand swings when multiple chargers start/stop
– Renewable shifting: store solar energy and use it later for EV charging
– Backup support: power essential systems or limited charging during outages (site-dependent)
Typical Use Cases
– Fleet depots with high overnight demand and limited grid capacity
– Retail and commercial sites with strict maximum demand limits
– Public charging hubs where grid upgrades are costly or slow
– Sites with solar PV aiming to reduce energy costs and CO₂ footprint
– Remote or weak-grid locations needing stable power for charging
Key Benefits of BESS
– Faster rollout of charging infrastructure without waiting for grid upgrades
– Lower energy costs through peak management and tariff optimization
– Higher effective charging capacity on constrained connections
– Better integration of renewables and improved sustainability reporting
– Enhanced reliability and optional resilience capability
– Increased revenue potential by serving more charging sessions at busy sites
Limitations to Consider
– Higher CAPEX and system complexity compared to grid-only sites
– Battery degradation over time reduces available capacity and power
– Requires correct sizing to match charging profile and business objectives
– Safety, permitting, and fire protection requirements can be significant
– Round-trip efficiency losses add some energy overhead
– Not a permanent substitute for grid upgrades if sustained high power is required continuously
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