This is Frank Weber, Global Vehicle Chief Engineer, Chevrolet Volt. I read with great interest “Dave G’s” post comparing the cost and range of extended-range electric vehicles (EREV) like the Volt to that of BEVs. While many of Dave’s numbers are estimates, his analysis is spot on and worth noting. EREVs have a distinct cost advantage – today and well in to the future – over pure EVs when vehicle range is the primary consideration.
Dave G’s Comment:
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OK, lets look at how a 70kWh BEV would compare against a 16kWh EREV if batteries were 1/4 of the price they are today.
The CEO from CPI (the company that builds the Volt packs today) puts the Volt’s battery pack cost at $8K. He is also the one that predicts the cost going to 1/4 of what they are today in the next 5-10 years.
http://www.greencarcongress.com/2009/02/profile-li-ion.html
Specifically, he says:
• The ratio of end-of-life to beginning-of-life is 75%.
• The AT application is sized for a 70% depth of discharge…
• A vehicle pack battery pack has non-cell costs such as a monitoring system.
These items together justify a 2.5x premium for the AT application (or approximately $ 1,000/available kWh) …
From a historical perspective over the past 17-18 years the cost has come down by a factor of 15x. In the next 5-10 years we should be able to come down by an incremental 2-4x and we will have to do that to accelerate the penetration of the technology.
So this says that the Volt’s battery costs $8K ($1000/ available kWh x 8 available kWh). We can also use the figure of $500/total kWh, since he says the total to available ratio is around 50% (i.e. 75% of 70% from first 2 points above). That means a 70 kWh battery pack would cost around $35K today. This sounds about right, since we know the 53kWh Roadster battery pack costs Tesla around $23K, and that uses high volume consumer electronic chemistry.
Now if batteries were 1/4 of today’s prices in 6-8 years, then the Volt’s battery would cost around $2K and a 70kWh battery would cost around $9K.
We also know that the ICE range extender (ICE, radiator, exhaust, etc.), costs around $2K. Keep in mind that we are talking about the wholesale cost for GM, not the retail price you or I would pay.
So the Volt’s range extender and battery pack would cost a total of $4K, while the 70kWh battery pack would cost around $9K.
Bottom Line: If battery packs cost 1/4 of what they do now, the 70kWh BEV would still cost $5K more than an EREV-40.. Since BEVs have serious issues refueling for long trips, the EREV is the clear winner for me. I don’t think I’m alone here.
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Below are two hypothetical examples of the cost advantage of the EREV approach.
The first chart compares the EREVs and BEVs based on today’s costs. This takes the very conservative approach of assuming manufacturers of BEVs have managed to drive battery technology costs to comparative levels (red line). The cost of GM’s battery technology is represented on this line. The cost of the range-extender moves the EREV technology slightly off the cost curve. However, even with the added cost of the range extending engine generator, the total cost of the system is still significantly below that of a limited range BEV, and the benefit – in terms of range – exceeds that of adding additional battery costs (pink area).

The second chart, applies the same logic, only this time under the assumption that battery costs will decrease by 50 percent. Again, the EREV approach has a significant cost advantage. However, it’s important to note that cost is just one of the reasons we believe the EREV approach is technically better. There are no compromises associated with an EREV. It offers the benefits of petroleum-free driving while overcoming range-anxiety. When the battery’s energy is depleted from driving in pure electric mode, the engine generator produces electricity to extend the Volt’s driving range to more than 300 total miles. And it can be the primary car for customers from places as cold as Kapuskasing, Ontario to as hot as Yuma, Arizona.

My compliments to Dave for his insightful post.




