An electric vehicle (EV) incorporates at least two separate electrical systems to manage its operational needs. The primary system is a high-voltage circuit responsible for moving the car, while a secondary, low-voltage system maintains the functionality of standard vehicle accessories. This dual-voltage design allows the vehicle to leverage high potential energy for propulsion while still utilizing common, standardized components for internal electronics. Understanding these two distinct voltage architectures is central to grasping how modern electric cars function.
The High-Voltage Propulsion System
The main battery pack in an electric vehicle, often referred to as the traction battery, is engineered to operate at a high potential to power the electric motor. This power unit consists of numerous individual battery cells connected in series to achieve the necessary high voltage. The established standard for most current electric vehicles is the 400-volt architecture, where the actual voltage typically falls within a range of 300 to 500 volts.
A newer, increasingly common design is the 800-volt architecture, utilizing a voltage range between approximately 600 and 900 volts. This higher potential system is becoming standard in high-performance and luxury models, though it is also appearing in more mainstream vehicles. Doubling the voltage requires a complete redesign of internal components, including the electric motors and inverters, to safely handle the increased potential. This shift represents an evolution in power delivery, allowing for greater efficiency and power output from the entire powertrain.
The Engineering Rationale for High Voltage
The decision to use hundreds of volts for propulsion is rooted in the physics of electrical power transmission. Electrical power is a product of voltage and current; to deliver a large amount of power, a system must have a high voltage, a high current, or both. Engineers choose to elevate the voltage because it allows the system to deliver the required power with a lower electric current. This reduction in current is important because the flow of electricity through any conductor generates heat, a phenomenon known as resistive loss. By halving the current, the energy lost as heat is reduced by a factor of four, which significantly improves the overall efficiency of the system.
A lower current also means that the cables and components carrying the electricity can be smaller and lighter. Thinner conductors require less copper, reducing the vehicle’s overall mass and cost. Furthermore, a high-voltage system is necessary to enable faster charging at high-powered DC charging stations. Since the charging station’s power output is limited by the maximum current the cables can safely handle, increasing the voltage is the only way to deliver more power and reduce charging times.
The Auxiliary 12-Volt System
Despite the sophistication of the high-voltage drivetrain, electric vehicles still incorporate a separate, low-voltage system, typically operating at 12 volts. This system is a direct carryover from traditional gasoline-powered cars because almost all standard automotive accessories are manufactured to operate at this voltage. These accessories include the headlights, taillights, interior lighting, the infotainment system, power windows, and various control modules. The 12-volt system also plays a role in the high-voltage circuit by powering the low-voltage relays necessary to safely engage the main traction battery. Unlike a conventional car, the EV’s 12-volt battery is recharged by the main high-voltage battery through a component called a DC-DC converter. This converter efficiently steps down the high voltage to the required 12 volts, ensuring the continuous operation of all the vehicle’s low-power electronics.