miniboes wrote:
- Density: the useful energy density (300% efficiency advantage included) for batteries is about 4% that of gasoline.
Which is ultimately the source of range anxiety.
Electric isn't ideal for long-distance commute yet, but good for daily work commute. Individuals and families need to stop buying cars based on the most distant possible commute, and start thinking about the more common commute: you can always rent a vehicle for a road trip (one which is both larger, and a hybrid so you won't have the range limitations).
Use a small vehicle with a short range for daily use.
This isn't an issue most of the time, consumers have to change the way they think about their cars. Since many families also have two cars, in the very least being smart about purchases could replace almost half of cars with electric.
miniboes wrote:
- Cost: if you include battery replacement cost, he calculates for the Tesla Roadster, Nissan Leaf and Chevy Volt that they are 4-7 times as expensive per mile as internal combustion engines with average efficiency.
I don't think he had any basis to make that claim. When do you replace the battery? At some arbitrary point? You have to look at the actual numbers for capacity loss until the point that it's no longer useable.
What you're dealing with is range loss:
http://www.greencarreports.com/news/1096801_tesla-model-s-battery-life-how-much-range-loss-for-electric-car-over-time
The battery doesn't simply stop working after eight years. Like all of us know who have owned a mobile phone or laptop, it just gives you less and less use time over many charges. Eight years is an arbitrary deadline for defects in the Tesla battery that make it stop working, not even a range guarantee.
I'll quote from that article a bit:
In the wake of more-rapid-than-expected battery capacity losses in Leafs in hot weather, Nissan now guarantees that the Leaf battery will retain at least 70 percent capacity after five years and/or 60,000 miles.
And that's pessimistic:
When Tesla first introduced the Roadster in 2008, it predicted that the battery pack would retain at least 70 percent of its capacity after five years and 50,000 miles of driving.
[...]
Using data from 126 Roadsters driven a total 3.2 million miles, the study concluded that the typical Roadster would still have 80-85 percent battery capacity after 100,000 miles.
The recent Model S numbers from The Netherlands are even more encouraging.
Based on 84 data points from the 85-kWh version of the Model S and six from 60-kWh cars, the study concludes that the Model S will retain about 94 percent of its capacity after 50,000 miles, with losses thereafter shrinking to about 1 percent per 30,000 miles.
Lead acid batteries are cheaper, sure: and I agree that it's possible they could make more sense in some cases. But for the vast majority of uses where a car can be plugged in overnight
and even at work or while grocery shopping, the user is only going to need about a 25 mile range (assuming no charging anywhere else),
That's a very old battery, given that it was originally over ten times that range.
https://www.fhwa.dot.gov/policy/2010cpr/execsum.cfm
The average automobile commuter spends 22.8 minutes commuting a one-way distance of 12.6 miles; bus commuters travel a shorter average distance of 9.4 miles, but have a higher average commuting time of 48.9 minutes.
You have already correctly identified that battery replacement costs have dropped:
miniboes wrote:
It seems like the prices of Tesla batteries have already dropped to around $20,000 (although I've had trouble finding a price from a reliable and recent source), where Richard Muller assumed $44,000 in his book.
You may have forgotten (as Muller seems to have too) to take into account the trade-in value. Lithium ion batteries contain a lot of very expensive recyclable materials: they take the old battery apart, and through a recycling process, make new batteries from it; or even just resell the batteries for less demanding use with different electronics (like home solar systems). They could even have several homes before ultimately being recycled for materials.
https://forums.tesla.com/forum/forums/tesla-model-s-85kw-battery-replacement-cost
Tesla apparently quotes 12k for replacement after eight or so years with the trade-in value (that was with their prepay program, though, I assume based on their estimates for the price with their new battery plant). Nisan is even less, as quoted in the article I linked to earlier:
By contrast, a Nissan Leaf replacement battery costs $5,500, after the trade-in allowance.
http://www.greencarreports.com/news/109 ... -over-time
That's a lower kWh battery, though perfectly suitable for commuting use.
Without the trade-in value, it's kind of like quoting the cost of a whole new refrigerator instead of a freon refill.
Tesla has an 8 year warranty with unlimited miles.
As mentioned, it should still be perfectly fine to drive with after eight years.
You need to use the range degradation numbers. While it's fine for most people to drive until it gets down to 25 miles, let's say 60 miles to be really safe.
Based on a 10% DoD, this site would suggest the battery would last well over ten years:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
Discharging batteries to a great depth is a good way to ruin them, basically. It shouldn't be necessary for cars used to commute.
(From that greencarreports article I linked earlier again) Starting range:
My 2013 Tesla Model S, when new, had an EPA range of 265 miles. But six or eight years down the road, with 100,000-plus miles on the odometer, there’s no way to know what my range will be.
We need to lose 205 miles for it to really need to be replaced. That's a 77% reduction.
Based on 84 data points from the 85-kWh version of the Model S and six from 60-kWh cars, the study concludes that the Model S will retain about 94 percent of its capacity after 50,000 miles, with losses thereafter shrinking to about 1 percent per 30,000 miles.
50k miles = 6%
+ 1% for each 30k miles.
Total = 50k + (30k * 71) = 2180k miles.
The it will cost you 12k to replace it.
That's about $0.005 per mile for replacement cost. Not substantial by any means. That's the best case, if your battery never outright breaks. And that's assuming there aren't any weird effects from low voltage as it loses capacity.
Some people try to avoid discharging it entirely (which is a good idea), although I assume that mile range has a buffer on it. You could look at what it would be avoiding lower than a 30% charge.
So, if we use a 47% reduction (to keep things above 30% charge):
Total = 50k + (30k * 41) = 1280k miles
At 12k, that's about 1 cent.
If we assume 20k, it's a little over two cents.
Still a much longer life than the eight years.
miniboes wrote:
The 8 years is probably on the short side, because Tesla would presumably put the warranty duration well below the average lifetime.
Yes, well, the 8 years has nothing to do with range. Computers last far beyond their typical one year warranties, for example. That's just an arbitrary line to inspire consumer confidence. It's possible your battery could break after that and your car just wouldn't start, in which case the number is closer to your calculation if you got
unlucky.
Somehow it seems unlikely that the battery would last 80 years, though, based on low useage driving. Storage time, and temperature, can affect the battery too, it's just not very clear how much. Lithium ion batteries seem to survive very well with a decade of storage, at least... but they've only been around for about 25 years, and only the oldest models can have been properly tested.
So, we really don't know how long these batteries will last.
miniboes wrote:If the problem of battery replacement cost is solved, the problem of charge time can easily be solved through replacing batteries instead of charging them. The idle batteries could be used as a back-up energy storage to compensate for irregular solar or wind energy.
This is very true. Solar and wind are much more suitable for powering cars than houses and industry, because the battery cost is already there, and if it's done in situ, at the storage facility it could be pretty efficient. Second hand batteries from cars also apparently increase availability of affordable batteries for in-home solar battery banks.
The whole energy source thing gets to his other point:
miniboes wrote:He goes on to calculate how efficient electric cars are if the electricity is produced with fossil fuels. This is 45% (fuel burned) * 93% (transmission line) * 80% (batteries charge and discharge) * 80% (electric motors) = 27%. Internal combustion engines are 20% efficient. If the electricity was generated by coal, which emits twice as much CO² as oil, the CO² emissions of the electric car would be higher.
Electric cars give us the
ability to get off gas, and onto something clean like nuclear to power our vehicles. It's still an important job to resist fossil fuel burning plants. The two have to go hand in hand to solve the problem of transportation emissions. Without electric cars, though, we don't have that option.
As you mentioned above, battery swapping could even make solar and wind more viable options.
In his calculations, he probably also failed to consider methane leak emissions from drilling oil, which are substantial.
miniboes wrote:Am I making sense? Do you think battery replacement costs will drop much lower?
I think they will. But even as expensive as they are now, I think it's viable.
miniboes wrote:
- Recharge time: Tesla boasts charging rates of about an hour, compared to up to 5 minutes for filling a gasoline car.
It's kind of irrelevant, though, because you can charge your car up in your garage at home -- you can't fill up your gas there. These things are different; gas isn't superior.
As mentioned before, there are also more charging stations spreading across the country (and quickly, because they're relatively cheap and easy to install compared to a gas pump). I've seen them at grocery stores, and a growing number of employers are offering them.
http://www.greencarreports.com/news/1076629_need-electric-car-charging-at-work-heres-how-to-get-it
Apparently, a company can even get a third party managed station for free (like a vending machine).