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Discussion in 'News' started by TEG, Dec 6, 2007.
(I moved a sidebar discussion on European vs US cars over here)
At the Town Hall meeting, Elon said "Tesla is relatively agnostic about how electric miles take place..."
They didn't exactly say what they intend to do, but mentioned "range extended EV", and said we should wait for "Whitestar announcement timing" to hear the actual plan.
This seems to further confirm that they are seriously thinking about series hybrids.
According to the Merriam-Webster Dictionary:
Agnostic: Noncommittal, Undogmatic.
I think this fits pretty well with what Daryl said. Telsa is not committed to using one particular battery type, and are not being dogmatic about believing that one type of battery is the best in every application.
Instead of "agnostic" how about "independent"...
good point. Thanks!
I like independent and flexible.
Perhaps I didn't make it clear enough, but like TEG said, what I am worried about is when the charge is depleted or near depleted. So I am saying that weak ICE+depleted battery produces less power than a fully charged battery with no ICE. This is of course refering to a series hybrid.
In battery sustaining mode, the main power is coming from the ICE. So it goes that the ICE has to at least be able to meet the power demands that the car has to meet to be able to sustain the battery charge or the charge will just continue dropping or you go into "limp mode" to prevent you from depleting the charge too quickly.
As I said this is fine with most driving, but as Tesla and Fisker are both performance oriented companies, I would expect cars would be put to the test at the track. This means extreme power demands throughout most of the course.
So there goes my comment that if a big ICE is needed then the PHEV really doesn't provide much efficiency in battery sustaining mode. But with a smaller ICE will the PHEV be able to keep up with power demands especially in a track setting (ie. not showing decreased performance in battery sustaining mode)?
Remember this? Marketing 2.0: More on the Volt
That's pretty funny, and somehow the Volt didn't make the top ten in the 2007 vaporware awards from wired.com and Tesla did. Anyways, it would be interesting when GM has a mule out and maybe that will answer some of the questions I have about series PHEVs.
The Chevy Volt is a good concept and in my opinion superior to something like the Toyota Prius. Pure BEV’s have advantages that shouldn’t be ignored either. One advantage is the life of the battery. The lower energy density cells in the Chevy Volt mean the battery must be recharged more often than say Tesla’s high energy pack. Batteries are only good for an X number of recharges before they degrade. Assuming the Volt and Tesla use the same battery type, their overall lifetime cost will be at least equal considering the Volt will need more frequent replacement though the Tesla pack costs more upfront. You see, its kind of a double edged sword. So now you have battery costs that are at least equal long term wise and one vehicle (Tesla) that has much lower maintenance. The other (Volt) has the same electric components that make it an electric vehicle in the first place with the added expense and problems that come standard with any internal combustion engine. You guys bring up a very good point though about the performance of the volt after the 40 mile discharge. I haven't thought of that before. Could be a huge downfall. Anyway thats just my two cents.
What about a series hybrid with a very small ICE that runs all the time?
When selecting batteries, there is cycle life to consider compared to energy density, but also max power output. In Tesla's case, people wondered if they use "4 or 5C" cells, but overtax them in short bursts (for quick 0-60). If you shrink the pack down (to save costs) then you start to have more of a problem with having to tax each individual cell more to get the same eMotor HP. If you took an approach where the ICE would always help, you could get away with cells with lower power output, and in exchange could probably select cells with better energy density and/or cycle life.
So, I imagine something with tiny ICE/generator ( < 30hp) that starts up as soon as you turn on the car. Then the controller mixes generator power and battery power to run the big eMotor. The upside is that you could have an "ICE assist" all the time so you would not need as much battery capacity or battery power output to achieve the same range / performance. Perhaps you use the ICE extender to make a 20kWh battery pack give a 400 mile vehicle range (on average) and still have high performance. There are a few downsides:
#1: It would be hard to call it a BEV anymore since the ICE runs all the time.
#2: The ICE would be keeping the batteries more fully charged on shorter trips, so the "all electric PHEV commute" wouldn't be so emissions free anymore.
The upsides would be:
#1: Lower costs than something with large BEV capacity.
#2: Full performance for a longer period because you would maintain battery reserves longer.
#3: Less electricity use per mile, so you could do 120V 12amp plug in to get full battery capacity quicker.
Driving habits dictate one approach over the other.
If Volt owners always have short commutes, and always plug in, then what they did makes sense. It really would be a short range BEV with emergency backup generator.
If people drive their cars frequently more than 40 miles between plug-ins then it would make more sense to have a smaller ICE that starts earlier.
Perhaps we need to keep thinking about something in-between where the ICE can be a bit on the small side, but it comes on earlier when it thinks you are intending to go on longer trips. (This could be a switch that the driver pushes which says "Long drive planned").
Unfortunately, marketing may dictate how the technology actually gets configured.
Volt seems to want to emphasize 100% BEV operation for as long as possible (so they can call the vehicle a BEV with "range extender").
I wonder what would sell better:
#1: A vehicle billed as a zero emissions BEV, but it will resort to using ICE if you ever exceed the BEV only range?
#2: A vehilce billed as a very high efficiency ICE with a BEV performance booster? (e.g. 80MPG Hybrid with 200hp performance)
GM could just have 2 drive modes. Long and short range. The motor would turn on much sooner (perhaps 75%) for the long range drive mode, and not activate until 30% for the shorter mode.
Taking this idea even further, they could just have a display on the console that showed current battery % left, along with a dial that allowed someone to set what % would activate the engine.
I also think the turbine is a fantastic idea. Turbines can run on almost anything and generally have a bit higher efficiency than the theoretical for a piston style ICE.
Even simpler solution: REEV/EV switch. In EV mode - no ICE, in REEV mode constant ICE help.
I do not see a downside.
A button for "ICE assist now please" is sort of the opposite of the Toyota Hybrid "EV mode" button that they finally offer on the 2008 Highlander. Outside of the USA, the Prius has had an EV mode button for a while, but for some reason Toyota had been slow to offer that feature here.
This all reminds me of the lengthy discussions we had about regen behavior on the Roadster. People wanted a regen strength knob or at least a button for "hill mode", but apparently they plan to leave it non driver adjustable.
They've said they would like to make it user-adjustable some time in the future, but the first cars won't have that feature.
That's because the Toyota hybrids are sort of the opposite of the Chevy Volt in the way they work. I think it was David Pogue who made a canny observation that in a Prius the electric motor merely assists the gas engine, whereas in the Volt the gas engine merely assists the electric motor.
So. . . A Prius uses the gas engine by default, and you need a special switch to tell it otherwise. A Chevy Volt will use the battery by default, until it runs down and the gas engine is needed. So, I suppose you could have a special switch to use the gas engine sooner.
I'm not sure how useful it is to really do that, though.
Is Tesla going to copy the GM Volt?
The Toyota synergy drive system is more sophisticated, complex, and advanced than some would say. The Prius (for instance) does plenty of BEV only driving on its' own. The "EV mode" button just says "I would prefer to run the batteries all the way down rather than have the ICE come on sooner." Due to cost and regulations their NiMH pack is so small that this "EV only" feature doesn't get you much BEV range, so it isn't all that useful in its' current form. Also, the Synergy eMotors are too small to offer highway speed EV mode.
Still we can see that we are in a "convergence" state with ICE motors getting bits of BEV technology, and BEVs thinking about taking on small ICEs.
By the way, there are a LOT of Prius owners where I work. Some of them bought the Prius saying "this isn't exactly what I wanted but it is the best I can do for now." They have been eying the aftermarket conversions that will retrofit in an EV mode button, or even turn it in to a PHEV with a bigger battery. I know there is at least some real amount of consumer interest in having a PHEV with an option to do EV mode driving on demand. Future generation Prius may evolve to have a bigger battery pack, plug-in recharge, and longer range "EV mode" button. I think this would be viewed as similar to a "REEV" (but REEV could have default EV behavior and a button to force the ICE on for longer trips instead of the other way around).
Yep I thought of that idea too, if you have the ICE constantly running you don't have to worry as much about battery reserves. However that would just turn the car into a plain series hybrid basically. I think the Volt is set out to be a range extended EV or REEV (as opposed to the PHEV name), with emphasis on the EV part, so I don't see them doing that. Though it would be interesting to have a button with that option, so during times that you know you will need extra power you can turn on the ICE earlier and not have to worry about the battery draining too quickly. It would be like the opposite of Toyota's EV button, as you said.
I touched on this earlier on. Like Michael said in his response to you, the Volt's batteries have a significantly higher charge cycle rating than Tesla's 500 charges. The a123 pack is quoted to handle 7000 cycles at the extreme but is guarantee for at least 4000 cycles.
Thanks for the response Darryl, I think I understand more clearly why Tesla chose the current cells for the Roadster. It has to do with higher energy density. There seems to be many more options opening up in the future and I look forward to hearing the strategy for the Whitestar in using these options.