Why 800V High Voltage System makes more sense for EVs?
Today, most electric vehicles use 150 to 400V DC link voltage battery configuration. The early electric vehicles used these voltages. Over the period of time, the majority of carmakers have accepted it as a standard. The 400V systems are most often called High Voltage systems and moving beyond 400V typically requires custom designs, which adds upfront cost. The commercial vehicle segment uses 800V dc link and beyond along with several high-end passenger vehicles.
800V System Overview
There is an emerging trend for 800V (and above) platforms lately. Major carmakers like VW, GM and Hyundai are following in the footsteps of start-ups such as Lucid Motors who have launched its first vehicle running on 800V systems. The high voltage systems for EVs are promising given the list of benefits it comes with, let’s dig deep into it.
Charging time
There is a convincing value proposition for 800V system over 400V system. Today, EV adoption is on the slower side mainly because of Range anxiety among the customer. This issue can be addressed by either providing higher battery capacity or reducing the charging time. The prior has its own consequences such as an increase in weight as well as the cost. The 40% of the vehicle cost today is for the battery alone. Reducing charging time is the area where 800V systems play an important role. In the 400V system, due to current limitations, we can only reach up to 200 kW DC charging. However, charging power can be doubled with 800V and hence charging time halves.
High-voltage Cabling
Cabling in an electric vehicle takes up a lot of space. This is why one of the simplest ways to reduce vehicle weight is to eliminate or reduce high-voltage cables. As the Voltage increases, the current requirement to generate the same amount of power will be 1/4 th than what is required for a 400V system. Further, conduction losses which are directly proportional to the square of the current (P=I2R) reduce by a factor of four.
Motor
In any PMSM, the speed is limited by power and voltage. While at max power the speed is directly proportional to Voltage. Increasing the rated voltage while maintaining constant power will increase the rated speed and reduce max torque.
Benefits of 800V system
- 800V is it improves overall vehicle efficiency by reducing joule losses
- High voltage cables can be downsized hence saving space.
- It enables Ultra-Fast charging capability.
- Smaller motor, conductors and cables due to lower current
- Reduction in overall vehicle weight.
- The driving range can be extended due to reduced weight.
- Optimum Vehicle cost as components can last longer.
- We can have a high power density motor.
- Possible to achieve a higher charging rate.
- To produce the same power output, the torque requirement will be lower.
- A simple cooling system is required for a high voltage system
Drawbacks of 800V system
- Deep design optimization is required
- A transition towards more expensive SiC and GaN MOSFET inverters.
- The cost of the Vehicle will go up because of an increase in the cost of a battery, BMS etc
- Need additional safety mechanisms to isolate systems from low voltage ECUs
- 800V battery pack has lower energy density.
Available 800V vehicles
| Model -> | Kia EV6 | Hyundai IONIQ 5 | Porsche Taycan Turbo S | Audi E-Tron GT |
|---|---|---|---|---|
| Battery | 800V | 800V | 800V | 800V |
| Battery Capacity | 77.4 kWh | 77.4 kWh | 93.4 kWh | 93.4 kWh |
| Range | 528 km | 507 km | 524-573 km | 472 km |
| DC Charging | 350 kW | 350 kW | 270 kW | 270 kW |
| Charging (0-80%) | ~18 min | ~18 min | ~22 min | ~23 min |
| Weight | 1,945 kg | 2,115 kg | 2,370 kg | 2,420 kg |
| Price | from $40,900 | from $43,650 | from $185,000 | from $99,900 |
Factors Influencing 800V adoption
| Charging Time | Range | Vehicle Cost | Direct Benefits | Safety |
|---|---|---|---|---|
 |  |  |  |  |
| Charge 80% in < 18 min | Travel 400+ km on a single charge | High upfront cost | No need to own a charging station | 800V systems are proven to be safe |
On a broader level, high voltage systems have more benefits compared to minor drawbacks. Further, as technology advances, the cost of these systems would go down and it will eventually come to mass vehicle segments. While we discuss 800V, carmakers around the world are already working on 1200V systems. We have a long way to go before it could turn into reality but we can definitely expect to see more EVs running on these high voltage systems soon.
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