bj33813

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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.

https://cleantechnica.com/2021/12/2...the-ideal-battery-size-for-its-electric-cars/
 

Torv

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Makes sense to me!

Clearly the secret is KW/h per kilogram of battery. Hopefully the technology will evolve to increase energy density per kilogram.
 
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JimBob

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There are two parts here.

One is battery efficiency and the second is battery size. When the Taycan came out in Nov '19 it had a bigger battery than most of its competitors but lesser efficiency. The result was a car that was extremely competitive in range with its competitors. Along with its other strengths it showed extremely well against everyone else.

In the short run, the newer cars that have come out or are coming out such as the Plaid/M3 LR/Lucid have increased battery size and often better battery efficiency. It will be interesting to see how Porsche responds to this. Pick performance over range?

I know I am happy with the performance but would like more range especially at the temperature extremes.
 

artdept

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I would like to drive from San francisco to downtown Los angels without stoping. (about 390 miles)
i think a 500 mile battery is sufficient.
 

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I personally prefer balance between size and weight, and honestly very few people in my opinion need to go 8 hours without stopping while driving (500 miles). I am completely happy for a stop every 2 hours if I can keep it to 10 minutes then its ideal (faster charge times).
 
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Tooney

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I personally prefer balance between size and weight, and honestly very few people in my opinion need to go 8 hours without stopping while driving (500 miles). I am completely happy for a stop every 2 hours if I can keep it to 10 minutes then its ideal (faster charge times).
I agree with not needing to make 500 miles without stopping. Shorter range is ok as long as I can stop for charging at a charging station that works. Put another way, if charging stations do not work reliably, actual range is unknown.
 

raharris

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I agree with not needing to make 500 miles without stopping. Shorter range is ok as long as I can stop for charging at a charging station that works. Put another way, if charging stations do not work reliably, actual range is unknown.
I think that is the crux of the matter; how far down the range can you run the car and be confident that is sufficient radius to find a working charge point. With gas, we have the luxury of knowing that there is (nearly) always a gas station within the range most of us are comfortable running our gas levels down to.

I would be less concerned about the ~200 mile range; if I knew, with confidence, there would be a working station at the ~160 mark... For now, I'll use one of my gas vehicles for the occasional longer drives I have to do - range wasn't a deciding factor in Taycan for me. Performance, handling and looks had me committing :)
 

JimBob

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I agree with not needing to make 500 miles without stopping. Shorter range is ok as long as I can stop for charging at a charging station that works. Put another way, if charging stations do not work reliably, actual range is unknown.
What I would like is to get away from having to preplan a trip to make sure you had your charging stations lined up ahead of time. Instead drive down to 15% SOC and then ask Porsche to find me a charging station that was actually working.
 

gnop1950

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What I would like is to get away from having to preplan a trip to make sure you had your charging stations lined up ahead of time. Instead drive down to 15% SOC and then ask Porsche to find me a charging station that was actually working.
I think this is coming, but it will be a while. As for long trips, let's just say that my wife and I are getting old enough that going for more than two or three hours without a rest stop isn't going to happen.
 

DL_AU

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Very interesting! One aspect of the article that was not well explained was how Porsche settled on 100kWhr as the ‘ideal’. They talk about a cycle of two hours of driving for 15 minutes of charging. The rough maths of this (I stress rough) would be something like this: 2hr driving at an average of 25kW would drain 50KWhr. Replacing this charge in 15 minutes would require an average 200KW charge rate. Is that achievable? For a 93kWh battery, 50KWh is roughly the difference between roughly 25% and 80% state of charge. Looking at the charge curve for a 93kWh battery, it looks like it will take between 15 and 20 minutes. The implication is that with the current vehicles it is already possible to to achieve something like a 2hr drive / 15 minute recharge cycle indefinitely.

With the smaller battery this cycle can’t be achieved indefinitely, but in practice it may be fine for a couple of cycles.
 

atebit

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“Six is too many, four is not enough” -Audi commercial c. 1975
 

Jhenson29

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Um, mark me down in the 500 miles without stopping category. We have a Silverado 3500 at work that can do around 600 miles (when lightly loaded). I can hit a 1000 mile trip with one stop.
👍👍

But, different vehicles for different purposes. Can’t optimize anything for everything.
 

ithinkmac

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Bathroom breaks? Who can drive 500 miles without stopping for a break?

-ThinkMac-
 

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