Four Key Challenges in Achieving Comprehensive Ultra-Fast Charging

Nowadays, electric cars are becoming more popular. Many concerns from ten years ago have been addressed, but one issue remains unchanged: fast charging.

Some think fast charging is just a matter of strengthening the car’s voltage circuit, batteries, and charging stations. Is it similar to the way smartphones upgraded from 5V/2A to 90W fast charging?

The solution to range anxiety Initially, electric cars faced range anxiety.

The direct solution was to increase the driving range to over 1000 kilometers under NEDC standards, eliminating anxiety.

However, today, most gasoline cars have a range of around 600 kilometers, and motorcycles rarely exceed 400 kilometers. The reason? Refueling takes 2-3 minutes, while charging takes much longer.

To solve range anxiety, we need to increase both the driving range and charging speed.

As of May 2022, there are 1.42 million public charging stations nationwide, compared to 110,000 gas stations. Considering an average of 6 fueling spots per gas station, public charging stations outnumber gas stations by at least 2 times.

Yet, queues form at charging stations for at least half an hour, while gas stations rarely have wait times over 5 minutes. New energy vehicles account for only 3% of all vehicles. The root cause is the slow charging speed of electric vehicles. The average charging time is 70 minutes, about 20-30 times longer than refueling a gas car.

Improving charging speed significantly reduces construction pressure on charging stations and eliminates driver range anxiety.

However, fast charging may not be necessary or achievable. Let’s discuss each factor.

Challenges on the vehicle side

Challenges on the vehicle side Firstly, achieving fast charging on the vehicle side requires increased power. Power = current × voltage. Increasing current and voltage both accelerate charging.

The preferred solution is to increase voltage since increasing current leads to significant heat generation. Increasing voltage while keeping the current constant increases charging power while maintaining heat levels. However, there are limits to charging voltage in consumer applications, with most flagship electric cars having charging voltages around 800V.

After 2019, most automakers had to find ways to increase current as the voltage limit was reached. This requires specialized batteries to handle the higher temperature generated.

Fast-charging batteries sacrifice some driving range to support quick charging. A car with fast charging may have an NEDC range of only 500 kilometers, while a non-fast charging car could have a range of 720 kilometers.

Manufacturers may also sacrifice battery lifespan to achieve fast charging. Using higher currents reduces the battery’s lifespan by half, but in practice, most cars will be sold or scrapped before reaching this limit.

Fast charging with high currents requires additional heat dissipation for each battery cell, increasing costs and car prices.

Challenges on the charging station side

Challenges on the charging station side Implementing fast charging on the charging station side is also challenging. High-power charging requires expensive power electronics to convert AC grid power to DC charging power.

The cheapest solution uses direct AC power, with no need for additional power electronics. However, more advanced charging stations with higher power levels need expensive power electronics, increasing costs.

Upgrading to ultra-fast charging stations (e.g., 400kW) requires significant infrastructure investment, costing millions of dollars per charging station.

The charging cables themselves become substantial at 400kW, requiring innovative solutions like liquid cooling to manage heat dissipation.

Demand for the electric grid upgrade

Electric grid requirements Even with optimal hardware on both the vehicle and charging station sides, achieving fast charging remains difficult. Fast-charging electric vehicles at scale poses challenges to the power grid.

A typical home uses around 10kW, and a fast-charging station serving multiple vehicles requires substantial power, potentially equivalent to the demand of dozens of households.

If all gasoline cars were replaced by electric vehicles and 1% of the total fleet needed fast charging simultaneously, it would require a power output equivalent to twice the current capacity of China’s entire power grid.

Practical limitations

Practical limitations Even with all the necessary hardware and infrastructure in place, achieving the advertised charging speed is challenging due to battery characteristics.

Most batteries can only sustain their highest charging power between 10% and 80% of capacity. Outside this range, charging power drops significantly. For example, above 80%, the charging speed may be only 1/20th to 1/5th of the maximum rate.

Tesla’s V3 Supercharger, capable of 250kW, only maintained its maximum power for about 160 seconds during a typical charging session, even though it theoretically could charge from 0% to 100% in 18 minutes.

In practical terms, achieving the advertised “30 minutes from 20% to 80%” charging time may mean a full 0%-100% charge could take around 120 minutes.

Conclusion In summary, achieving true fast charging for all-electric vehicles is almost impossible and may not be necessary for most users. The need for a 5-minute charge for a 200-kilometer range is rare, and the majority of users can charge overnight at home.

For those who do need rapid charging, battery swapping might be a more viable solution.

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