Fast forward twenty years, and although lithium-ion (Li-ion) now dominates battery chemistry, other aspects of battery packs have evolved only modestly. Operating voltages have gradually increased to around 400V; capacities can be as low as 17kWh in mini cars, while high-end performance vehicle batteries can exceed 100kWh. Beyond incremental improvements in battery design, EV capacities are expected to continue rising slowly. Significant changes, however, are coming in operating voltage. Enter a new generation of EVs, such as Porsche’s Taycan shown in Figure 1, which replaces the 400V battery with an 800V system.
Forget 400V – 800V is on the Way
2022. 10. 31
The year 1996 marked a milestone in electric vehicle history with the launch of the General Motors EV1. The EV1 was the first mass-produced, purpose-designed electric vehicle from a major automaker and the first GM car engineered from the ground up as an electric vehicle. Early EV1s used a lead-acid battery with a capacity of 16.5–18.7kWh and an output voltage of 312V, while Gen 2 vehicles adopted a nickel–metal hydride (NiMH) battery with 26.4kWh capacity. Unfortunately, the market was not ready for the EV1, and production ended in 1999.
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How a Higher Voltage Solves EV Challenges
Why the shift to higher voltage? Two major obstacles for EV adoption are limited driving range and long recharge times. Ultra-fast charging helps address both, but current-generation DC fast chargers for 400V EVs typically deliver only 50–60kW at 480+ volts and 100+ amps. This can fully charge a 100-mile range EV in just over 30 minutes.
For 400V battery EVs, charging rates are constrained by the practical cable size needed to carry high currents. Increasing the current generates additional heat in the battery. Temperatures exceeding the safe operating range in Li-ion batteries can reduce performance and, if extreme, trigger exothermic reactions, thermal runaway, or fire. Higher voltage enables lower current for the same power, reducing overheating and improving energy retention. This enhances driving range and allows for weight reduction, as less copper is required in the vehicle’s electrical system. Smaller motors can be used, freeing space for additional battery capacity and further increasing range.
For 400V battery EVs, charging rates are constrained by the practical cable size needed to carry high currents. Increasing the current generates additional heat in the battery. Temperatures exceeding the safe operating range in Li-ion batteries can reduce performance and, if extreme, trigger exothermic reactions, thermal runaway, or fire. Higher voltage enables lower current for the same power, reducing overheating and improving energy retention. This enhances driving range and allows for weight reduction, as less copper is required in the vehicle’s electrical system. Smaller motors can be used, freeing space for additional battery capacity and further increasing range.
Reliability and Safety Considerations for 800V
New 800V DC fast chargers can deliver 150–350kW. Designing an 800V EV, however, demands careful attention to all electrical systems. DC voltages at this level are lethal on contact, even though lower DC voltages are generally considered safe.
Consequently, system reliability requirements are stringent. High-power three-phase EV chargers require mechanically robust plug connections and dependable electronic safety systems. The vehicle’s battery management system maintains continuous communication with the charging station. Power flows only when the charger plug is securely seated and the battery charger continuously signals “ok.” Any interruption immediately triggers the charging station to disconnect.
Consequently, system reliability requirements are stringent. High-power three-phase EV chargers require mechanically robust plug connections and dependable electronic safety systems. The vehicle’s battery management system maintains continuous communication with the charging station. Power flows only when the charger plug is securely seated and the battery charger continuously signals “ok.” Any interruption immediately triggers the charging station to disconnect.
As Figure 1 demonstrates, high-power EV chargers, regardless of output voltage, rely on multiple low-power internal supplies to establish a fault-tolerant, safe, and reliable power infrastructure. These include:
Not only charging stations need thorough monitoring; the EV battery itself requires constant observation. Advanced Li-ion batteries are usually arranged into several modules. The current, voltage, and temperature in each module need to be monitored separately to ensure that the charging process keeps within the SOA of the battery. It has to be possible to switch off individual modules if they fail while continuing to supply power to the healthy modules. A complex electronic system is vital in battery life maximization and failure protection for individual cells.
Even as EVs with 800V batteries start to appear, most chargers will still use 400V, so the new 800V EVs are capable of using either a 400V or an 800V charger. Other 400V models have been designed for an easy transition to 800V operation when the market dictates.
- AC/DC converters for auxiliary power, safety interlocks, and control circuits with overvoltage category 3 (OVCIII) protection according to IEC62477-1.
- Isolated DC/DC converters for gate drivers, sensors, and input isolation.
- Non-isolated DC/DC converters for internal distributed power architecture and dual-rail analog circuits.
Not only charging stations need thorough monitoring; the EV battery itself requires constant observation. Advanced Li-ion batteries are usually arranged into several modules. The current, voltage, and temperature in each module need to be monitored separately to ensure that the charging process keeps within the SOA of the battery. It has to be possible to switch off individual modules if they fail while continuing to supply power to the healthy modules. A complex electronic system is vital in battery life maximization and failure protection for individual cells.
Even as EVs with 800V batteries start to appear, most chargers will still use 400V, so the new 800V EVs are capable of using either a 400V or an 800V charger. Other 400V models have been designed for an easy transition to 800V operation when the market dictates.
What EV Charging Solutions Does RECOM Offer?
RECOM offers a range of low-power AC/DC modules, DC/DC converters, and switching regulators tailored to auxiliary supply requirements in fast DC chargers.
For instance, RECOM’s RAC05-xxSK/480 was designed for monitoring in the charger shown in Figure 2. The AC/DC converter operates at input voltages up to 528V AC, easily handling two phases in a three-phase system. Isolated up to 4kV, the 5W converter transforms three-phase power into low DC voltages of 5 or 12V for monitoring electronics. Its auxiliary power also drives the handshaking system that ensures power flows only when all systems are operating correctly.
RECOM also provides a non-isolated 3.8VDC/3A supply for wireless interfaces: the RPL-3.0, a compact 3mm² buck converter with integrated inductor, featuring adjustable output and full protection (SCP, OLP, OVP, OTP, UVLO).
RECOM Power Systems can deliver high-reliability custom battery chargers, conditioners, and bidirectional inverters based on proven platform designs from three-phase AC supplies with power ratings up to 30kW or higher when units are paralleled.
For instance, RECOM’s RAC05-xxSK/480 was designed for monitoring in the charger shown in Figure 2. The AC/DC converter operates at input voltages up to 528V AC, easily handling two phases in a three-phase system. Isolated up to 4kV, the 5W converter transforms three-phase power into low DC voltages of 5 or 12V for monitoring electronics. Its auxiliary power also drives the handshaking system that ensures power flows only when all systems are operating correctly.
RECOM also provides a non-isolated 3.8VDC/3A supply for wireless interfaces: the RPL-3.0, a compact 3mm² buck converter with integrated inductor, featuring adjustable output and full protection (SCP, OLP, OVP, OTP, UVLO).
RECOM Power Systems can deliver high-reliability custom battery chargers, conditioners, and bidirectional inverters based on proven platform designs from three-phase AC supplies with power ratings up to 30kW or higher when units are paralleled.
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