The size of the battery in an electric car has a direct relationship to how much it costs to manufacture, how fast it can charge, how much range the car will have, how well it performs on track, and how quickly it accelerates, among other things. As Porsche contemplates the transition to electric cars, its designers and engineers have needed to ask themselves a question: How big should the battery be to satisfy the expectations of Porsche owners?
In a blog post, Porsche says the size of the battery in an electric car is fundamentally responsible for the carbon footprint of the vehicle. Yet it is also the component that determines an electric vehicle’s success on the market. The size of the battery must be the right size to make sure the vehicles meet customers’ expectations and requirements.
The company says it is working diligently to determine how big the battery in its electric cars should be in order to meet all the expectations of its customers. For example, they value a dynamic driving experience, but at the same time expect their vehicles to cover long distances quickly with short charging times.
Most people believe a larger battery is needed for dynamic performance, however, simulated lap times at the Nürburgring suggest otherwise. Porsche has calculated that a virtual Taycan Turbo S featuring an 85.1 kWh battery and weighing 2419 kilograms can complete a lap in 7:39.5 minutes.
When the battery capacity is reduced to 70 kWh, the total vehicle weight goes down to 2310 kg, but the reduction in battery power means the Taycan takes an extra seven tenths of a second to complete the lap. The lower vehicle weight makes it possible to accelerate from zero to 100 km/h in 2.90 seconds, which is 0.02 seconds faster than the reference vehicle, but with this configuration the Taycan takes 9.51 seconds to reach 200 km/h, which is around eight-tenths of a second slower. These calculations indicate that an overall weight saving does not compensate for the reduced power of the battery.
A 100 kWh battery adds an extra 107 kg to the total vehicle weight. Despite the more powerful battery, the lap time increases to 7:42.4 minutes, accelerating from zero to 100 km/h takes 3.04 seconds and zero to 200 km/h takes 9.71 seconds. The influence of weight becomes even clearer with a 130-kWh battery, which increases the total vehicle weight to 2743 kg. With this configuration, the lap time increases to 7:48.2 minutes, accelerating from zero to 100 km/h takes 3.28 seconds and zero to 200 km/h takes 10.48 seconds.
800-volt technology & DC charging
Porsche’s findings indicate that, while a smaller battery is the better option for reducing CO2 emissions during production, a medium-sized battery delivers the best driving dynamics. Large batteries are generally believed to offer a greater range plus shorter journey times. However, thanks to its 800-volt technology and highly efficient direct current charging process, the Taycan takes just 5 minutes to store enough energy to cover an extra 100 km. Most studies recommend a ratio of two hours of driving to 15 minutes of charging, and the Taycan is already capable of covering long distances when driven in this way.
Porsche acknowledges that a larger battery — 100 kWh for example — can reduce travel times but believes future battery developments will allow it to find the “sweet spot” it is searching for with a medium size battery. That doesn’t mean it may not offer larger batteries as an option for drivers who are more concerned with range than stellar performance on the race track.
Reducing Carbon Emissions
In line with the policies of the entire Volkswagen Group, Porsche is committed to significantly reducing the carbon footprint of its cars and its manufacturing process. Its second generation electric vehicles — which have yet to be launched — will generate about 25% less carbon dioxide during their life cycle than first generation models. New cell technology will reduce energy consumption while higher charging capacities will improve efficiency, the company says. In addition, an increase in the proportion of raw materials available from recycled batteries promises a big improvement in sustainability, which will give Porsche a real chance of achieving its target to be carbon neutral across its entire value chain by 2030.
Almost half of all the CO2 emissions generated during the lifecycle of an electric vehicle are produced at the manufacturing stage, which includes the extraction and processing of raw materials. The second largest source of emissions is determined by the energy mix used to charge it, charging efficiency, vehicle efficiency, and driving style. Recycling procedures and further processing of materials at the end of a vehicle’s life cycle generate the lowest proportion of CO2 emissions.
The company is continuing its normal, highly rigorous engineering approach to deliver electric cars that will feature the scintillating performance its customers expect, the range they need, and the lowest carbon footprint possible. Keep in mind that everything Porsche knows, the rest of the Volkswagen Group knows as well. That’s good for those of us who dearly want the EV revolution to succeed.
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