The myth of Megawatt charging – and why Porsche doesn’t think it’s the answer to smoother EV journeys | usagoldmines.com

While the battle for EVs with the longest range may well have tapered off, a new arms race has begun in its place – and it’s all about charging speeds.

In China, some of the world’s most recognizable automotive and tech brands are dueling it out to see who can force electrons into a battery pack at the most impressive rates.

After all, if said giants of industry can consistently bring charging times in line with fueling up an internal combustion engine vehicle, range anxiety is essentially banished to the history books and the extra weight, resources and financial penalties of larger battery packs are no longer an issue.

But while the so-called Megawatt ultra-fast charging (anything above 1,000kW) has tongues wagging with the sheer physics-bending nature of it all, some believe that the road towards two-minute top-ups won’t be so smooth.

During a recent electric vehicle battery technology workshop at Porsche’s R&D facility in Weissach, the company spoke frankly and at length about its own road to electrification, marking the huge leaps it has made with the current generation Taycan and what the future holds.

When asked about the current trend for Megawatt charging, Porsche’s development lead in high-voltage lithium-ion batteries, Carlos Alberto Cordova Tineo, said that while it is impressive, he doesn’t think it is the future for everyone.

“It is relatively easy to demonstrate this sort of level of ultra-fast charging on a test bench, but making it work in the real world is a much more difficult task. There are just so many factors to consider when charging at these rates,” he told me.

One of the key issues for Porsche is battery longevity, as the company wants its cars to offer the same sort of driving thrills in 20 to 30 years time as they do when they roll off the production line.

Current residual values of Porsche’s EVs aside, the company’s cars generally remain hugely sought after items, with many going on to become collectable objects.

“All lithium-ion batteries suffer an initial 2-5% capacity drop in the first few years, but it is our job to manage battery health for the remainder of the vehicle’s life,” Cordova Tineo adds.

One of the factors that can lead to “sudden death” in a battery – or the point where its performance rapidly drops below what is deemed normal – is consistently charging at extreme rates, which Cordova Tineo says can lead to lithium plating and a massive reduction in battery performance.

“It is why we use stepped charging, where power is gradually ramped up as the battery reaches the optimum state of charge, tapering off as it hits the 70 or 80 per cent mark and then slowing right down towards the end,” he explains.

Real-world results

While Porsche wouldn’t rule out any new innovations in electric vehicle charging, it isn’t hastily jumping on the Megawatt bandwagon for now.

Otmar Bitsche, senior consultant in battery development and one of the longest-standing EV engineers at the company, says that the charging figures coming out of China are “good for PR but not always practical in the real world”.

“The physics of it all is complex and this is before we even consider the infrastructure required to make it work,” he added.

During one real-world demonstration in China, Inside EVs reported that BYD’s Han L, which is the first to use its Super e-platform with the latest Flash Battery, would draw 767kW of power until it reached a 40% State of Charge (SoC), holding steady at 633kW until it reached 50% and then dropping to 463 kW as it reached 60%.

Overall, the car gained 262 miles in around five minutes. Impressive stuff.

But despite BYD’s claims that fast-charging the battery doesn’t affect the warranty, the technology hasn’t been around long enough for us to know what state it will be in after five or ten years, long after the warranty has run out.

Plus, most of these next-generation, ultra-fast Chinese packs use a lithium-ion phosphate (LFP) chemical make-up, rather than the nickel manganese cobalt (NMC) that is used by Porsche in its Taycan and Macan models.

Right now, Porsche is working to recover around 90% of the raw materials used in its NMC battery packs in order to drastically reduce the reliance on mining.

Recycling fast-charging LFP batteries, on the other hand, is widely considered a more complicated task and presents a weaker business case due to lower economic value of their content.

Driving dynamics matter

The other key factor for Porsche is driving dynamics, arguably one of the most important pillars of the brand.

Even its everyday electric SUV, the formidable Macan, is an absolute hoot to drive and will give many modern sports cars a run for their money on the race circuit.

Otmar Bitsche, senior consultant in battery development, says that there is a delicate balancing act to be had with overall weight, energy density and charging speeds, the perfect concoction of which will go into the marque’s long-awaited electric sports cars.

Both the upcoming 718 Boxster and Cayman are due to feature the next generation of Porsche’s EV powertrains, with Bitsche claiming that a range of around 370 miles on a single charge would be “enough” for most sports cars.

The company’s current 800V architecture allows for a max charging speed of 270kW, which is enough to brim the Taycan’s larger battery pack from 5% to 80% in just 22.5 minutes.

Expect the Boxster and Cayman to feature smaller packs and new onboard charging tech, which in turn will likely see them charge even faster.

It is this notion of “being enough” for most users that Bitsche reiterates when confronted with the subject of Megawatt charging speeds, as he feels the additional technology and hardware required to make it work, not just from the manufacturer but the charging networks, has potential negative effects on the way a vehicle drives and a company’s bottom line.

An ultra-fast future

Just this week, the Society of Automotive Engineers in the US just released a new SAE J3400/2 standard that defines the way a 1,000kW-capable North American Charging Standard connector and vehicle charge port will look like, proving its confidence in the technology.

However, as some critics have pointed out, even the Chinese real-world demonstrations only ever creep up to 1,000kW for a matter of seconds during charging sessions, before tapering off to a steady 600-odd kilowatts and then dropping back further.

As a result, some industry insiders believe it would be more beneficial (and cheaper) to build out a reliable network of 500kW chargers that can deliver those kind of speeds for a larger proportion of the charging session.

This would equate to 8 to 10-minute stops for many, which is the equivalent to the time spent at most gas stations, according to one white paper.

Finally, and perhaps most importantly for a marque like Porsche, Megawatt charging is still a relative unknown, with little research available on the longevity of the battery technology after many years or the reliability of it in extreme weather conditions.

“Increasing the charging efficiency and decreasing charge times is one of our priorities,” explains Dr. Matthias Goldsche, a physicist and battery expert at Porsche.

“But this isn’t the only thing, as we think the next generation of cars can hit a sweet spot of acceptable daily range for the majority of our customers, fast charging speeds, driving dynamics and the ability to create long-lasting, reliable and recyclable batteries,” he adds.

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