Navigant Research Blog

Beyond Ultra-Fast Charging: Part 1

Scott Shepard — May 31, 2017

Now that the continued decline in battery prices can make battery EVs (BEVs) cheaper to drive than the competition, ultra-fast charging is viewed as the final link to making them mainstream. Given that, the automotive industry is focusing on approximating the time it takes to gas up by rolling out ultra-fast charge networks in North America and Europe.

Tesla’s success with the supercharger network supports the above assumption, but there may be flaws in the ultra-fast charging concept relating to the basics of batteries. The primary component being that charging at a power capacity (measured in kilowatts) higher than the BEV’s battery energy capacity (measured in kilowatt-hours) stresses the battery, reducing its useful capacity over time. Most of the upcoming vehicles capable of accepting an ultra-fast charge will likely have battery capacities between 30 kWh and 80 kWh, whereas upcoming ultra-fast chargers can provide 120 kW-320 kW or more, 4-10 times the battery’s energy capacity.

Reducing Side Effects of Ultra-Fast Charging

Automakers and charging networks can develop systems to diminish the cumulative effects that ultra-fast charging has on batteries (as recently evidenced by Tesla). These solutions are effectively reducing the charging rate under certain technical and ambient environment conditions, limiting the value-add of the fast charging. Such limitations haven’t yet been seriously evidenced because the fastest charging today is only operating at around 2 times the battery capacity. Most charging generally occurs at sub-1X rates.

Only when BEV owners primarily rely on fast charging over slow charging will these limitations become more common and more concerning to potential customers. This is more and more likely given the increasing range of BEVs alongside the development of the ultra-fast charging networks. The advances in BEV and charging technologies mean that BEVs will no longer be limited to single-family homeowners with a reliable charging station in the garage. Indeed, many without residential parking spaces (and therefore charging equipment) may now view the long range BEV an option so long as they can fast charge.

Such ambitions should be tempered through consumer education efforts and/or the development of more modest slow charging options in long-term parking structures. This unfortunately further complicates an already complicated pitch to the mass market. It also threatens consumer consideration of electrification or limits use of the ultra-fast chargers themselves. However, such concern is warranted to avoid negative shifts in consumer perceptions.

Overall, as long as BEVs are primarily purchased by single-family homeowners, this potential problem is probably marginal. However, for the future transportation modes dominated by automated vehicles, it is likely a non-starter.

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