Instead of curb rash on the rear wheels, we can look forward to curb rash on the rear side quarter panels. Fun times ahead
That's what autopark is for!
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That's what autopark is for!
With a turning circle the size of Texas, by the look of things.
Do both the front and the single rear wheels steer?
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All things being equal, 80% frontal area combined with this drag number, Tesla only needs a 40kWh battery pack, and with minimum gigafactory price reductions the pack will have a maximum price of $9000, but will probably be much cheaper than that. I would bet actually that their entire powertrain will cost less than a comparable car, i.e. BMW 3 or Audi A4. That's quite an inflection point where both the initial cost and operating costs of the car is less than an ICE counterpart.
40kWh would _suck_, because the impact of difficult conditions would be _far_ greater. Heating in cold weather, rolling resistance from rain, crosswinds and so on.
Given that
1) Capacity reduction increases the impact of time-based loads
2) Aerodynamics can be disturbed by crosswinds
3) the key aim of the Gigafactory is to lower cell and battery prices with a target of reaching $100/kWh
4) Tesla's approach has given them an energy density advantage over competitors
5) Higher capacity increases charging power, which increases charging mph, which reduces (a) journey time (b) Supercharging time
6) Higher capacity increases range, which decreases the need for Supercharging which reduces (a) journey time (b) Supercharging time
I think that using aerodynamics as a capacity-cutting measure is absolutely the wrong approach to take for Gen 3. The cost savings would be limited, diminishing as battery prices continue to fall, and it would be at the expense of utility. I think it would be much better to use the aerodynamics in a positive way that also leverages any density advantage to differentiate from more conventional competitors. I'd argue that they'd have more appeal at the value end by cutting back on performance of the base model instead. At the $35k price point there are plenty of cars with 0-60 7s or higher, and that includes very popular BMW 3 Series diesels.
We're talking about the base model. You can get 2-4x improvement in heating draw by using a heat pump, which is just the AC in reverse cycle. Rolling resistance and rain will both be reduced by body shape and narrower tires.
dgpcolorado
high altitude member
Except that heat pumps typically don't work well in very cold weather. Which is when the energy savings is actually needed.
I really hope that the Model 3 doesn't have rear wheel fairings and tight tire/wheel-well clearances. It is tough enough to deal with packed-in snow and ice in conventional wheel wells. Smooth wheel covers, fine. I'd also be concerned with radical designs that have a tapered rear because of greatly reduced space utility and awkward rear hatch access.
Overall, I guess I don't buy the idea that Tesla will hit a < 0.20 Cd for the Model 3. I'd be surprised if they did it.
Commercially available air source heat pumps are rated down to -13F. That's technology a couple years old.
Mad Hungarian
Member
Doesn't the MS already use a heat pump, with resistance as a booster? I would expect this to also be the case for M3, seems crazy to use resistance-only when you look at what that costs in range.
Heat pumps that are rated for low temperatures also don't operate as efficiently in warmer conditions. Those heat pumps also won't necessarily translate to automotive applications. The Leaf's heating system is of little help at lower temperatures.
Fundamental rule is: capacity ~ range ~ power ~ charging speed ~ 1/discharge rate.
In reducing the capacity Tesla would:
- increase the swings in range depending on conditions which means that Tesla
- - needs to build more Supercharger capacity
- lower maximum charging kW which means that Tesla
- - loses the gain in charging mph you could have had from improved highway efficiency
- - adds charging time needed to deal with HVAC and other time-based losses
- - needs to build more Supercharger capacity
- lower average range which means that Tesla
- - needs to build more Supercharger capacity
Not only would the cost savings on batteries be less than $2k per 10kWh, diminishing to $1k (Tesla hopes) per 10kWh, but some of those savings would be lost to higher Supercharger infrastructure costs and the cost of offering the additional pack size.
I sincerely hope that Tesla doesn't have to reduce the pack size to 40kWh to hit $35k. That would be a really bad sign.
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No, the Model S uses heat captured from the motor, which reduces the need for resistive heat.
Mad Hungarian
Member
RobStark
Well-Known Member
Rear and/or Front fender skirts can be detachable and optional.
Repaired or replaced after accident.
Repaired or replaced after accident.
If your efficiency is above 100%, then it is of use. Maybe you don't get the 300% as usual, but fine. Most winter conditions, it saves a lot of energy.
I think the leaf is of little use, so no valid comparison there.
You're making the assumption they use the same chemistry and cell internals optimized for the same charge/discharge rates. This is not a good assumption. 40kWh also has a huge advantage, which is charge time/circuit size needed at home. All of a sudden 110v charging becomes almost bearable, and 240V charging becomes very fast. That also means 3rd party charging stations also become more useful.
stopcrazypp
Well-Known Member
The Leaf system is actually fairly relevant, esp. given the Model 3 will be the same price range. See the discussion here:
http://www.mynissanleaf.com/viewtopic.php?t=12212
Not sure how true it is but that thread says the heat pump equipped Leaf is less efficient when using AC in warm weather.
