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EV Topics: The Status Quo & Trends of 800V High Voltage Charging Technologies

Views:0     Author:EDC 电驱未来     Publish Time: 2021-05-07      Origin:EDC 电驱未来

Original Author: EDC电驱未来

Translate & Edit: Andy, Kewell 


#taycan #Hyundai #BYD #China #ChinaMarket


Introduction

It’s true that EV stands out in many aspects, powertrain system, noise, and cost-in-use, not to mention the long endurance models (over 1000km) presented by industry leaders. EV falls short in the respect of charging process. To solve the issue, the industry is looking to high voltage platforms and super charging pile solutions.

Two questions will be answered in this article:

a)What is high voltage platform?

b)What are the preconditions to make a high voltage platform come true?

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New infrastructures built for EV


Going black-out used to be a very common event during the 80s and 90s in China. As the grid system improves and with the completion of ultra-high voltage transmission line, it is no longer a daily matter to the people in China.

The same idea applies to EV as well. Through raising the voltage level, energy can then be transmitted in high power.


Limited by the voltage withstand of silica-based IGBT power semiconductors, 400V voltage platform was commonly adopted in the EV industry. The highest charging power at present goes to Tesla with its third-generation super charging pile, reaching up to 250kW, and peak current near 600A. However, 400V is not enough if we wish to raise the charging power to further reduce the charging time.



Porsche Taycan Turbo S is the first model to be massed produced in 800V platform in the industry with 350kW as its maximum charging power. Capable of charging up to 80% in 22.5min. (index 5%) for its 93.4kWh power battery, enough to sustain 300km. 


Charging speed is redefined by this new, super charging pile with 800V platform and 350kW power level. Not only is it much faster than the 120kW DC charging pile, but also resembles the come-and-go experience as we have with the ICE vehicles at gas station. It’s a blessing to those who rely on the public charging facilities or those who can’t install one at their own households. The maximum charging power is looking to reach above 600kW after the landing of new national standards for super charging pile in China, according to some insider analysis. “5-minute stop, 200km to go” is about to come true.


Another merit about this high voltage platform is that you get to reduce the overall weight of wires, which can be an important factor to consider for installation. The principle is simple. On the premise of the same power level, the higher the voltage there is, the fewer the current runs through therefore thins the wire.



Take Taycan for instance. The cross-sectional area of wire is cut by half as the voltage doubles from 400V to 800V, with current dropping by half. 4kg of weight in total is reduced.


A simple idea but complicated to realize

Seemingly an easy task to ramp up the overall voltage of a vehicle, it’s a huge project that involves many disciplines to develop such application. A high voltage platform at 800V, 1000V or even higher values, brings higher voltage requirements for the other components within a vehicle, the three-electric system, air compressor, DC/DC converter, and on-board charger etc.

Take battery pack for instance. Voltage can be increased simply by adjusting the string and parallel numbers of cells. The real technical challenge lies at safety usage and service life as high voltage/current working conditions may present uncertainties.



Studies suggest, overvoltage or overcurrent at charge may cause side reactions and instabilities to electrode materials and electrolyte. Lithium may get separated out on the surface of negative electrode, ultimately resulting in rising resistance, capacity fading, and in extreme cases, fire and explosion.

The *C-rate of battery packs has reached 2C in general at present. Through utilizing electrolyte additive, isotropic graphite, graphene and other materials, conductivity of battery materials can be improved to a certain extent, and the stability of ternary materials under high voltage working conditions can be enhanced. However, these solutions cannot prevent side reactions from happening essentially. A few major technical issues lie ahead of this super-fast charge solution in respects of battery materials, BMS control precision, and so forth.


In addition, high charging power would bring major challenges to the cooling system of battery. Positive electrode, where the heat builds up, will require focused treatment to stay within safe working temperatures.


Take electric motor system for instance, the ramp up of voltage will also bring additional demands on the level of insulation, voltage withstand, and creepage distance, which in turn affects the design and costs of electric components. Fortunately, resources and experience are rather well placed in this field of application. The real challenge lies at the core part of motor control unit, power semiconductor. As one of the most used power semiconductors, silica-based IGBT voltage withstand reaches up to 600V-750V, meeting the standard requirements of cars. However, at high voltage platform, there are not as many choices for IGBT that can withstand 800V, not to mention it’s still carrying with high-loss and low efficiency defects.


Featuring high voltage withstand and thermal conductivity, industries began to look to this new solution, SiC materials, to develop relevant technologies. SiC MOSFET, for instance, started to outshine in the high voltage platform as its voltage withstand and energy loss level surpasses the others, and it’s looking to reach 1200V.

Falling short in respects of productivity and costs (VS. IGBT), there is still a long way to go for SiC materials to go widely adopted. The penetration rate of SiC MOSFET is projected to reach 20% or so in Y2025 according to some industry experts. IGBT will remain as the major market offering for power semiconductors for another few years in the electric drive system.


For other parts in a vehicle, AC compressor, PTC, DC/DC converter, and on-board charger etc., technologies for high voltage platform are underway as well. According to some industry insiders, relevant mass production is expected to be completed within this year. Once the industrial chain becomes mature, production costs can then be significantly reduced.

Contrary to high voltage platform, the development of super charging pile went rather smooth as no extra effort or change is needed to be done to the core parts of it, except the charging gun, cable, contactors, and fuse, which need to be selected according to voltage levels.


The layout of car companies in high voltage platforms

Introduced by Porsche in Y2019, Taycan was the first model to be mass produced for 800V voltage platform, but as a “forerunner”, Porsche also assumed the development risks and challenges of this new technical frontier. Strictly speaking, it was not entirely built for 800V platform as limited by the development progress of each component. In addition, they made a concession on the charging speed of battery to some extent.

To be compatible with an 800V platform, a converter (800V/400V) is placed before the 400V AC compressor. To be compatible with a 400V charging pile, Taycan is also geared with a DC on-board charger to ramp up the voltage level from 400V to 800V for battery charging.


Utilizing power conversion application, Porsche has spared no effort in developing solutions to reduce the overall charging time of EV. It is believed that, with high voltage components and fast charge technologies in place, the following generations will likely be compatible with 800V platform entirely based on 350kW charging power.

The 800V DC charging system of Taycan Turbo S can support 350kW, charging 75% in 22.5min. for its 93.4kWh battery, enough to sustain 300km. As battery technologies improve, the system may even extend to 400-500kW power levels.



Great as it is, not everyone can afford this high-end, luxury car. Out of economic perspective, Hyundai developed a pioneering solution, the E-GMP platform built for 800V, to present customers with rather friendly market offerings. IONIQ model, for instance, has been introduced to the market.

Charging system of the E-GMP platform utilizes drive motor and inverter to ramp up the 400V power input from the charging pile to 800V.


Hyundai also revealed that the SiC power module applied in the E-GMP platform enables its energy efficiency to raise by 2%-3% for the electric drive system, and the overall endurance is raised by 5%.

Determined to develop 800V platform, Mercedes-Benz, General Motor, and Jaguar have presented their own platforms in succession. In addition, Volkswagen has also started the Trinity project expecting to realize 800V super charge technology in Y2026.

In China, BYD is one of the forerunners to layout in relevant technologies. Utilizing high voltage IGBT solution, they are able to ramp up some of their models’ voltage levels to 600V and above. Tang, for instance, a new energy vehicle of BYD, reaches up to 700V.


BYD Han is equipped with their self-developed SiC power module. With existing base of technologies, BYD can surely save some effort to bring higher voltage platforms.

Creator of the SEA EV platform, Geely plans to introduce 800V high voltage platform and SiC power module into its products, with super charge function of “5-minute charge, 120km to go”. Such vehicles are expected to be mass produced this year.


A promising future but distant to realization

A grand future may be awaiting EV with the introduction of high voltage platforms and super charging pile technologies. Industries are still bound by some certain issues.

For OEMs, they are concerned about the infrastructural work of supporting facilities for high voltage platforms as well as the new national standards for high power charging.

For charging service providers, it is of great uncertainties to invest heavily in super charge facilities when the market volume is not there yet.

Mutually concerned. It’s time for the government to step in and direct the two industries.



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