Column: Electric Vehicles
Solving the 400V/800V EV
fast-charging incompatibility problem By Haris Muhedinovic, Sr. Field Application Engineer EMEA Automotive, Vicor
O
EMs are increasingly powering electric vehicles (EVs) with 800V batteries, for higher performance,
more powerful powertrains and faster charging times. However, in DC fast charging there are incompatibility issues between 400V and 800V charging stations. To fast-charge 800V EVs, owners must use compatible charging stations, not the 400V DC ones that are more prevalent today. Not
only are they not compatible with the newer EVs, they also have considerable limitations in current capability, cable thermal management and voltage range – an incompatibility that limits driving range and is a potential impediment to the adoption of EVs. There are two main solutions today to
this problem: one, to expand or modify the existing charging stations network, and, two, to make vehicle onboard chargers compatible with any DC fast charging stations.
Addressing incompatibility The incompatibility problem is focused on DC charging, which is commonly used for long-range driving where time and access are limited. AC charging is normally not a problem since the existing grid infrastructure is suitable – it is readily accessible, either at home or work. AC charging is ideal for daily use and short-range driving, where charging speed is not critical – it is the cheapest and most practical solution for daily trips to 300km. For longer distances, however,
vehicle charging should be quick since it is situated at public places, such as motorway stations and rest stops, where turnover of vehicles is extremely high. That’s why the preferred charging stations are DC. They require over 50kW of power, reaching 150kW or 350kW at peak. Whilst DC charging may be used
less frequently than AC charging, it’s important to have a solid network of them to reduce range anxiety. In 2020, the DC charging network numbered about 400,000 fast chargers, with only a few supporting 800V vehicles – in Europe, just 400 of 40,000 charging stations support 800V vehicles. This imbalance between 400V
Figure 1: With battery virtualisation, the charger “sees” a 400V battery on one side of the onboard charger even while the 800V battery is connected to the other side
and 800V charging stations is fast becoming a significant problem as OEMs begin rolling out new 800V vehicles: the public infrastructure to charge them is inadequate.
www.electronicsworld.com December/January 2023 17
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