Tesla Motors

The Tesla Roadster is a very cool concept.  It's a battery driven sports car with great performance and a 250 mile range.  That's better than any other all-electric car that's been manufacturered.  Note that it's not a hybrid, but a true all-electric running on Li-Ion batteries.  They're specifying 100,000 miles of 'useful battery life.'

The batteries are the weak part of the system.  Previous all-electrics used standard car lead-acid batteries, but the Roadster uses Lithium Ion.  I've heard that Li-Ion batteries can lose about 20% of their storage capacity per year.  And that they have a useful life of 200 to 300 charge-discharge cycles.  It's worse as the temperature of the battery gets warmer.  Cars are hot even without an internal combustion engine.  I'm concerned that the useful life of the batteries in the Tesla might only be two or three years.  It could be that the range of the car would be cut in half after 2 years.

What might the replacement costs of the batteries be?  As a order-of-magnitude kind of estimate, they might be storing 250 to 500 Mega Joules in the batteries to get their 200 to 250 miles range.  I'm estimating that it costs about 10 to 20 cents per KJ to get the storage.  I'm guessing the cost of replacing the batteries is 25 to maybe 50,000 dollars.  Although I prefer to buy, I think I'll lease this car! 

They rightfully brag about their operating cost of electricity being around 1 cent per mile.  Compare that to my car which the gasoline costs say, 3.50 per gallon and at 20 miles/gallon, you're paying about 18 cents a mile.  Of course, the real cost of operating the vehicle is probably 4 or 5 times that considering all factors, but I'm just trying to compare engine to engine, not tires and insurance, etc., which would be the same from vehicle to vehicle.  Now what if we consider the costs of replacing the batteries?  If we assume 100k miles and the low end of my replacement estimate, you come up with about 25 cents per mile.  So the cost of the batteries far outweighs the cost of the electric over the lifetime of the vehicle.  But the good thing is that it's not outlandishly more than the cost of gasoline.

I'm very interested in the Roadster, but need to know more about the battery life, and the replacement costs of the batteries.  I don't really plan to keep a car longer than 100k, but what if the batteries need to be replaced after 50k miles?  or even 25k? I was joking earlier about the lease, because the lease will ultimately take into account the depreciation of the batteries.

I am certainly interested if any readers can improve on the crude estimates I've made.

Comments

[Aelothir]

All I know on the battery front is that the main designer of the vehicle has a background in battery power. He has proven in the past with some of his products that he can squeeze many hours of life from Li-ion batteries whilst keeping the product light. If anyone is going to work out how to get more than 300 useful charges out of the batteries, its him.

That said however, the cost of replacing the batteries is not prohibitively expensive when compared to petrol and diesel cars (or gasline as you yanks say) and perhaps governments of the future, with the environment in mind, may help with the cost of keeping the car stocked with batteries.

[Aelothir]

Oh, and if you're interested, check out my blog at www.mind-camp.blogspot.com.

[Greggums]

I think you're right that the battery life would be about three years. They claim that their proprietary Li-ion batteries last 500 charges. If you recharge the car every other day, it'll last about three years. This is definitely not a car for the masses. What's so encouraging to me is that they know this and are marketing it as a high-end sports car. It's a good first step, something they can built on.

[WRAY EDWARDS]

TOSHIBA HAS TOTALLY SOLVED BATTERY LIFE (TEN YEARS) AND VASTLY SHORTENED CHARGING TIME WITH NANO-TUBE TECHNOLOGY. PROBLEM SOLVED...BUY...DON'T RENT.