Cars

Batteries in electric cars: Stop in growth in sight

The variety of battery electric cars is increasing. With the differentiation, however, it becomes visible that the energy content – ​​colloquially the capacity – of the electrochemical storage correlates directly with the vehicle segment. A microcar has to be cheap, so it has less of the valuable cells between the axles. The fact that the little ones are usually only used to commute to work, kindergarten or shopping fits in well with this. It is diametrically the opposite in the battery-electric luxury class: With a Mercedes EQS or a Porsche Taycan, there is a requirement to be able to cover long distances at any time with ease. In addition to the large capacity, there is a high charging power, which in practice translates into a rapid charging speed. How are the individual classes developing?

The situation with traction batteries is actually a success story. In the past ten years, the cost per kilowatt hour has fallen by more than 80 percent, some say even more than 90 percent. Manufacturing economies of scale and continuous improvement in cell chemistry have made this advance possible. Lately, however, voices from the industry have been increasing, which speak of a stop to this trend or even a slight price increase. The reason for this is that raw material prices are rising sharply.

Specifically has the trading price of lithium year-on-year roughly quadrupled. Nickel has also become significantly more expensive at around EUR 30,000 per tonne, and cobalt, where the price is around EUR 78,000 per tonne, has never been cheap. The reduction in the proportion of cobalt in the NMC cathodes commonly used in Europe to ten percent is compensated for by the increase in the proportion of nickel to eighty percent in the so-called NMC 811 cells. It is therefore plausible that the majority of the LFP cells (for lithium iron phosphate and therefore free of nickel or cobalt) already produced and sold in China will be sold worldwide by 2024 in the majority of electric cars can be found – in Germany this is currently only the case with the Tesla Model 3.

However, due to the pressure from the CO₂ fleet limits in the European Union, the car industry is dependent on selling more and more battery-electric cars. Electric cars are included in the CO₂ balance with zero grams because only the emissions on the car are recorded directly. In our opinion, this CO₂ fleet mechanism will mean that the battery capacities in the respective vehicle classes will either stagnate or only increase slightly.


Fiat 500e

Fiat 500e

The small Fiat 500e can be ordered with a net energy content of 21.3 or 37.2 kWh. Because the segment is price-sensitive and a long range for the trip to the supermarket or the sports field is not necessary, battery capacities of this magnitude are unlikely to be exceeded in the medium term.

(Image: Christoph M. Schwarzer)

Example Fiat 500e: The customer can choose between a battery with 21.3 kWh or one with 37.3 kWh net capacity. While in most vehicle classes in which such an option exists, the larger of two batteries is used, this is not necessarily the case with the micro cars. The basic price is 26,990 euros (all information without subsidy) for 21.3 kWh and 30,990 euros for 37.3 kWh. The equipment may be a bit better, but in the end the money is the deciding factor as long as the purpose is fulfilled.


Loading curves

Loading curves

C rate made visible: The blue charging curve is the fastest way to charge the 37.2 kWh battery. A C-rate of 1 indicates that 1 kW of charging power is feasible per kWh of battery capacity. In this case, a C rate of 2 is only briefly exceeded.

(Image: Fastned)

Whether this works also depends on the charging capacity or the charging speed. This in turn depends on the C rate. 1C corresponds to one kW of charging power per kWh of battery capacity. So if the large battery in the Fiat 500e (test) can be charged with up to 85 kW for a short time, that’s over 2C.

Manufacturers cannot increase the C rate at will. One reason for this is that the stress on the cells increases at a high C rate and this can promote wear. The automotive industry therefore limits the charging capacity via software. In the cold, the charging capacity decreases anyway for various reasons, such as the increased viscosity of the electrolyte.


VW ID. 3

VW ID. 3

In the case of compact cars, once known as the Golf class, around 60 kWh is the customer’s sweet spot, i.e. the best compromise between range and price. In the VW ID.3, the 58 kWh battery dominates over the 77 kWh version. With the new Kia Niro EV, the entry-level battery of the predecessor with around 40 kWh has been eliminated; only the ’64 stainless steel is available.

(Image: Christoph M. Schwarzer)

In any case, we are guessing that the microcars will stagnate at a level of 30 to 40 kWh, while in the compact class it should be a good 60 kWh by 2025. The compact class means the VW ID.3, but also the Renault Megane e-Tech or the Kia Niro EV. Until recently, these three offered a choice of two battery sizes. The majority of buyers opt for around 60 kWh. That could be the reason why Kia has deleted the small battery (39.2 kWh) without replacing it. Although 77 kWh can also be ordered for the VW ID.3, the customer choice in this segment is the 58 version. Around 60 kWh seems to be the sweet spot, the best compromise between costs and range.


Loading curves

Loading curves

More battery capacity equals more charging power: the size 77 battery in the VW ID.3 is blue, the size 58 green. The C rate remains roughly the same. An extreme increase in the C-rate is not to be expected, because excessive charging increases wear on the battery. Manufacturers are gradually approaching the sensible maximum.

(Image: Fastned)

Volkswagen has moderately increased the charging capacity of the modular electrification toolkit (MEB), but does not go far beyond 2C at the top: According to a presentation, the ID.Buzz, the fastest charger among the MEBs, could achieve over 170 kW charging capacity with the 77th generation -kWh battery if it is delivered from autumn 2022.

In addition to the price, the battery capacity and charging capacity are also the highest in the sports and luxury classes. As usual in the automotive industry, it shows what is technically possible when money plays a subordinate role. A Mercedes EQS has an energy content of almost 108 kWh and a charging capacity of 207 kW. The fact that it is not even more than the Porsche Taycan with 270 kW is partly due to the 400-volt architecture of the EQS; the Taycan uses 800 volts. This is a rarity so far, but will continue to spread.


Mercedes EQS

Mercedes EQS

With almost 108 kWh of energy content, the Mercedes EQS marks the pinnacle of battery storage. In the luxury segment, money plays a subordinate role.

(Image: Christoph M. Schwarzer)

The upcoming Premium Platform Electric (PPE) from the Volkswagen Group, for example, will have a battery voltage of 800 volts. The Porsche Macan EV or the Audi A6 e-tron will be based on the PPE. The Kia EV6 (test) and the Hyundai Ioniq 5 (test) already have an 800 volt system. With Platform 3.0, BYD even offers the combination of 800 volts and LFP cells, which is unique. These electric cars from BYD are not yet exported to Germany. But that is likely to change in the coming years.


Loading curves

Loading curves

The maximum charging power of 207 kW is clearly exceeded by the Porsche Taycan with around 270 kW. The reason for this lies in the voltage level of the Porsche, which is 800 instead of 400 volts.

(Image: Fastned)

According to current assessments, there will not be unlimited growth in battery capacity and charging capacity. On the contrary, little will happen until the middle of the decade. The nice idea that cell chemistry would develop as rapidly as the power of computing chips with falling prices did not materialize. In this way, the end customer is primarily offered the battery size that is most appropriate for the purpose of use and the vehicle class. The smaller, the less. Even at the very top, where the air is getting thin, unlimited growth cannot be assumed.


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