Nominal voltage is the standardized reference voltage assigned to an electrical system or device (for example 230 V, 400 V, 480 V, 800 V). It represents the intended operating level under normal conditions, used for design, labeling, and compliance—even though the actual voltage can vary within allowed tolerances.
Nominal voltage in EV charging
Nominal voltage is used across both AC infrastructure and EV batteries:
AC charging and site electrical systems
– 230 V nominal: common single-phase line-to-neutral supply in many regions
– 400 V nominal: common three-phase line-to-line supply in many regions
– 480 V nominal: common three-phase supply in parts of North America and industrial sites
Nominal voltage determines current levels for a given power and affects cable sizing, protective devices, and charger configuration.
DC charging and EV battery systems
– EV battery packs operate at a nominal DC voltage (often ~350–400 V or ~700–800 V depending on architecture)
– DC fast chargers must support a voltage range around the battery nominal voltage (because battery voltage changes with state of charge)
Nominal voltage helps define charger compatibility and maximum power capability at a given current limit.
Why nominal voltage matters
– Enables consistent system design and equipment selection
– Drives current calculations (lower voltage requires higher current for the same kW)
– Affects cable cross-section, losses, and thermal performance
– Impacts protection coordination and safety design
– Helps determine whether a charger can deliver its rated power at the site’s supply voltage
– Supports interoperability and clear technical documentation across markets
Nominal vs actual voltage
Actual voltage can differ from nominal due to:
– Utility supply tolerances and grid conditions
– Voltage drop over long cable runs
– Site load changes (peak demand events)
– Transformer tap settings and distribution design
EV chargers may reduce power or fault if voltage goes outside acceptable limits.
Common examples and terms
– Line-to-neutral voltage: nominal single-phase voltage (e.g., 230 V)
– Line-to-line voltage: nominal three-phase voltage (e.g., 400 V)
– Voltage range (DC): charger supports a minimum to maximum DC output voltage (e.g., 150–1000 V)
– Derating: reducing power output when voltage or temperature conditions require it
Related glossary terms
Line-to-neutral voltage
Line-to-line voltage
Three-phase charging
Single-phase charging
Voltage drop
Maximum charge current
Peak charging power
DC fast charging
Transformer capacity
Power quality monitoring