Tesla S vs. The Volt

Pretty impressive info on the Tesla Model S. Interesting stat on the Volt losing 40% during the winter in range loss.

DBCassidy

 

That's not surprising and I don't know, how the review missed that one.

In winter, with heater on full, the Ampera/Volt, draws 6kW for heating. In half hour drive, that's 3kWh, that's 30% of the (10kWh usable) battery capacity of the Ampera/Volt.
If we assume, that Model S draws the same amount of energy for heating, that's 6kW and it consumes 3kWh in half hour, at 60kWh battery pack (let's say 40kWh usable), the reviewer has, that's only 7.5% of the usable battery capacity against the 30% of usable capacity of the Ampera/Volt.
It all depends on the battery pack capacity, not so much efficiency.

If I use Hold mode in the beginning of my 2012 Ampera winter journey, to heat the passenger cabin with ICE heat, I can make the same distance in the winter as I do in the summer.

 

That was a surprisingly positive comparison for the Volt vs. a $75k + Model S.

This past winter I used very little electric heating in commute weather that dropped as far as 35-37F for a few days in the San Francisco Bay Area. My EV range reduction in winter was within 10% and I kept my average efficiency better than 270 Wh per mile from the wall. I made my morning 45 mile drive without using the gas engine on all but 2-3 days where I had to use gas for the last couple of miles.

If I had the slightly longer range of the 2013 model Volt I would have made it even then. I've driven 49,000 miles (32,000 EV) in 2.5 years and haven't perceived any EV range loss from the battery pack yet (although there might be some that is hidden to me as a driver).

 

Tesla is way more sexy looking than the Volt. Musk is on the right track. Heck, Tesla sales numbers leave the Volts' sales numbers in the shadows.

DBCassidy

 

Only if you defy the laws of physics.
Yes, heating takes up a lot of power and therefore range. However, every car is affected by the increased air density in colder weather as well as increased rolling resistance in snow and from winter tires (if you use them).

 

Are you saying the heater uses 6kW all the time it is on? A 2.4kW bar heater will warm a small room, the inside of these cars must get hot! Do any of these high tech marvels use reverse cycle heat pumps for heating? It would make sense as the compressor etc. is there already for cooling.

 

I live in a climate considerably cooler than San Fran, and over the last 6 months (winter + spring) my Prius vagon has averaged 240 Wh/mile of petrol energy calculated after the powerplant (ICE).

 

Yep, drive on the petrol engine at the start of the journey instead of at the end, that is just sensible in winter to get that heat you will end up dumping at the end of a journey anyway if you can't make the journey on electric alone.

I'm not sure where the extra energy comes from to crush snow and move rain but. Of course if you live where it doesn't snow, like sensible people ...
Added air density? I don't think it would have a measurable impact unless at high speeds. Do we have any experts in that field?

 

Not an expert, but I imagine the change in density is the inverse of the ratio of temperatures on the Kelvin scale. Since overcoming air friction is about 50% of total energy use at 70 mph (110 kph), this suggests that a drop from say 30C to 0C would increase fuel consumption about 5%, all else staying the same.

Of course the colder temp also increases oil viscosity, so the effect of cold goes beyond rougher roads and heavier air to push around.

 

We've had snowy roads just about maybe 10 days in the whole winter. The rest was clear roads.
At least Ampera (I don't know about the Volt) has the official option to put different winter tire size, which is 205/60/16, summer tire size is 215/55/17. I bought one of the best, by ratings, and most low rolling resistance tire, which is Continental WinterContact TS830P XL, which are even much quieter than the factory summer low rolling resistance tires Michelin Energy Saver, so I didn't notice any measurable difference in range between the summer and the winter tire.

In eco mode, it's 2kW, in full mode it's up to 6kW and on cold days that can mean 6kW for quite a long time. Consider you have to warm up the air and the objects in the cabin, which can be as cold as -10°C to 23°C.
And you're not heating only the cabin air, because you have to bring in some fresh air constantly and you have to warm fresh air from up to -10°C to 23°C.

That can certainly be the case, but it's the same for any car. However, I don't notice it that much, because I have my Ampera parked in a -2nd floor of underground garage, where it never dropped below 10°C and never goes above 20°C in the summer.

 

Google agrees:

 

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Some do, and I'd be surprised if the Tesla didn't. The Leaf skipped it because of price, but that may have changed with the 2013 model. It's just that for places that have a winter, these onboard heat pumps won't cut it, and a secondary heater is needed for when it gets actually cold.

Also keep in mind there is less insulation than a building, 6 surfaces vs 5 to lose heat through, and a constant stream of cold air moving over said surfaces.

 

Thought this was interesting:

Officially Official: Tesla Is Top Selling EV Maker In The US, Increases Sales Estimate For 2013

DBCassidy

 

That sounds impressive. It would be interesting to see your math.

I'm getting roughly 220 Wh per mile measured after the battery (not including charging inefficiencies).

 

Hi Jeff,

I used these numbers:
50 MPG (currently at 50.4 after 21k miles.)
33,400 Wh/gallon source fuel
36% thermo efficiency estimated

So ...
33,400 * 0.36 = 12024 Wh to the driveshaft
12024 Wh / 50 miles = 240 Wh / mile