Low Voltage, Extra-Low Voltage, and High Voltage
Battery systems span a wide voltage range, and the safety and design requirements change significantly at defined thresholds:
| Voltage range | Classification | Key implication |
|---|---|---|
| ≤50V AC / ≤120V DC | Extra-Low Voltage (ELV) | Reduced shock risk; SELV/PELV/FELV categories |
| ≤60V DC | Low Voltage (LV) | Safe working voltage threshold in automotive |
| >60V DC | High Voltage (HV) | Mandatory isolation, HVIL, PPE requirements |
| >1000V DC | Very High Voltage | Specialist HV standards apply |
The 60V DC threshold is the critical boundary in automotive battery design. Below it, component sizing and safety requirements are manageable with standard approaches. Above it, the design must address creepage and clearance distances, mandatory isolation monitoring, interlock systems, and a complete set of HV safety procedures.
→ Extra Low Voltage (ELV) → Higher voltage packs
12V
The 12V system voltage limits are quite well defined by the automotive industry as there is a need for all of the components to survive.
48V
The 48V system is synonymous with the MHEV, but has been adopted for a range of other applications. Keeps the system below 60V DC and hence it is possible to build a lower cost system.
400V Architecture
400V Architecture can mean many things as claims are often made based on the maximum system voltage rather than the nominal battery pack voltage.
800V Architecture
Doubling the pack voltage halves the current in the busbars, contactors, connectors etc. At a cell level there are small changes, mostly based on the reduced losses in the busbars leading to a small reduction in power demand.
400V vs 800V
The choice of pack voltage architecture is one of the most consequential early design decisions in EV and BESS development.
At a given power level, current = power ÷ voltage. Doubling the voltage halves the current, which halves I²R losses in conductors, halves the cross-sectional area needed in busbars, and reduces the physical size of contactors and connectors. It also enables faster charging — a 350kW charger at 800V delivers ~437A, versus ~875A at 400V.
The tradeoff: 800V requires more cells in series, more demanding isolation requirements, and components rated for higher voltage. Charger infrastructure at 800V is less widely deployed than at 400V, though this is changing rapidly.
Split-pack charging bridges the gap — an 800V drive pack is split into two 400V sections connected in parallel during charging, allowing compatibility with 400V infrastructure. Used in production in the Porsche Taycan, Audi e-tron GT, and several other platforms. → Bank Charging
See also: High Voltage System, Pre-Charge Resistor, Battery versus System Voltage