[Interview] How Did Tesla Develop EV Battery? (page 2)

Dec 20, 2010
Naoshige Shimizu & Kouji Kariatsumari, Nikkei Electronics

Q: Why did you use a battery with a capacity as high as 56kWh? The Leaf EV, which Nissan Motor will release in December 2010, will come with a battery with a capacity of 24kWh, which is less than half that of the Roadster's battery.

Kelty: We are developing EVs under the concept of "no compromise." This means that we are offering the same convenience as that of gasoline vehicles to EV users.

We did not want to say, "Its drive range is shorter because it's an EV," to our users. That's why we equipped the Roadster with a battery with a capacity of 56kWh and ensured a drive range of 394km under the US LA4 mode, which is equivalent to the drive range of a gasoline vehicle.

Another reason is that there was an extra space in the vehicle body. If not, we would have employed a battery with a lower capacity though it would not have been half of the current capacity.

The Roadster has the 56kWh capacity battery, but the EV is normally used in a mode in which the battery is charged up to about 90% of its capacity to reduce the load on the battery. To charge the battery to 100%, the mode has to be switched to the "Extended Range" mode. We consider it sufficient because the capacity of the battery will not be fully used in normal driving conditions.

Q: For the "Roadster 2.5," which will be released in Japan, you will offer a fee-based service of exchanging batteries. The 56kWh capacity battery can be replaced only for ¥1.26 million (approx US$15,005). Why is it so inexpensive?

Kelty: It is a forward-looking price. If the vehicle is purchased now, its user will replace the battery after about seven years. Depending on how the vehicle will be used, it might be ten years. At that point, this price will be reasonable.

Q: In addition to the Roadster, you are planning to develop the "Model S" electric sedan and co-develop the "RAV4 EV" with Toyota Motor and another EV with Daimler. Do you intend to use the 18650 battery for them, too?

Kelty: If the prices of automotive batteries will drop, we do not have to stick to the 18650. However, they are still expensive at this point.

Currently, we are evaluating battery cells of various battery makers. We do not intend to have an exclusive relationship with one battery maker. For the vehicles that we will develop from now, we will use batteries of several makers.

However, we will not bother to disclose the names of those battery suppliers. When general consumers purchase notebook PCs, they do not care about the names of battery makers, do they? I believe that the same thing can be said to EVs.

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