spatterso911
P100DL - Raven
My question is... For the Fisker Karma drivers... What does the Karma do in very cold weather? Does it use battery power to warm the cabin, or does it get heat from the ICE?
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Propane has about the same energy per kg as gasoline, so you'd need a pretty big propane tank to match even a 5 gallon gas tank which would provide something like 20 hours of cabin and battery heat at around 15F. Propane tanks are also big and heavy and difficult to fill on a highway.
Chiming in from the Land Of Perpetual Cold (-27ºF/-33ºC on the first day of spring here, for example..... 
), my suggestion is to, indeed, consider propane rather than gasoline. It is far less messy, AND I would ixnay anything like a 5-gallon gas or its equivalently-sized propane tank. Instead, make use of a campstove-sized, refillable propane tank. The reason? From my read of posts in this forum, almost all of you drive very small numbers of miles on each hop (for me, for example, it's a 200-mile one-way trip into town....and that's over the Alaska Range, too). A propane tank of even 1-liter would be more than enough to get you to/from almost any reasonable drive, and you also can throw a few extra small bottles into your frunk.
), my suggestion is to, indeed, consider propane rather than gasoline. It is far less messy, AND I would ixnay anything like a 5-gallon gas or its equivalently-sized propane tank. Instead, make use of a campstove-sized, refillable propane tank. The reason? From my read of posts in this forum, almost all of you drive very small numbers of miles on each hop (for me, for example, it's a 200-mile one-way trip into town....and that's over the Alaska Range, too). A propane tank of even 1-liter would be more than enough to get you to/from almost any reasonable drive, and you also can throw a few extra small bottles into your frunk.Tesla should offer a propane or ethanole powered stirling engine with a generator for drivers in very cold climates ... that way you could get electricity AND heat. A cold soaked MS battery with its liquid cooling/heating system would make a great heat sink for a Stirling engine to improve efficiency even further.
A liter would last a bit over an hour, but there's no issue with such short drives as there's plenty of battery power for both traction and heating. The problem comes when the drive is long enough that the battery limits are being approached.Chiming in from the Land Of Perpetual Cold (-27ºF/-33ºC on the first day of spring here, for example.....
While handling gasoline can be messier than propane, there actually is a well established technology and infrastructure for using gasoline in vehicles. I'm very doubtful that carrying several loose bottles of propane would be as safe as gasoline in a built in tank. I've seen small propane tanks leak which would be pretty scary in an enclosed area like the frunk, so I'm not sure how Tesla's lawyers or government safety regulators would feel about such a design. Stopping every hour to replace the propane bottle doesn't sound very convenient and at $3-4 a pop, it wouldn't be all that inexpensive either.
JRP3
Hyperactive Member
At $400/kWh, the price per kWh difference between the 60 and 85kWh packs, the extra 3.5kWh would add $1,400 and at the 150Wh/kg pack level density that's an extra 23kgs. Neither would seem like a deal breaker, especially since an alternative heating fuel system would not be free.
Sure, but that's only for 30 minutes of heat. If you want to do a 30 minute drive, just use the battery in the car, there's plenty for that short a drive.
However, what if you want to drive over 200 miles in cold weather between charges? That's going to be more like 3 1/2 hours. Based on people reporting a 20% or more reduction in range for temps in the low teens F, that's going to be over 16 kWh for cabin and battery heating.
JRP3
Hyperactive Member
Maybe the better answer is for Tesla to switch to a heat pump system. They are supposed to be much more efficient, the Zoe uses one.
stopcrazypp
Well-Known Member
I thought the Model S already uses a heat pump system (which is why it has so many heat ex-changers).
JRP3
Hyperactive Member
If that's true then wouldn't it take less than 3.5 kWh of pack energy to deliver 3.5 kWh of heat?
Well I believe the data for how much power it takes to heat the car and battery comes from actual owners' experience. Given that, whatever the method is of delivering the heat, the amount needed seem to be in the range of 6-7 kW. My understanding is that they use a heat pump, but that only works if they've got heat to pump. I believe they use the drive train waste heat as the source, but I've not heard that they try to use sub-freezing ambient air and am a bit doubtful that would work very well.
stopcrazypp
Well-Known Member
Heat pump efficiency approaches 1 at 0 degrees F (-18 degrees C). I also remember reading that they do use coolant from the drive-train as a heat source (similar to how an ICE does it).
I think we have to keep in mind the Model S is heating both the cabin and the battery pack, whereas EVs like the 2012 Leaf is heating only the cabin.
I think we have to keep in mind the Model S is heating both the cabin and the battery pack, whereas EVs like the 2012 Leaf is heating only the cabin.
glhs272
Unnamed plug faced villian
At my work we are installing Espar Airtronic diesel fueled cabin heaters for our Canadian customers. I am considering installing one of these in my model S. I think this would be a valuable feature for extreme cold conditions like we have been having this winter. I wouldn't need 99% of the time, except for when I need to push every bit of range from my car on road trips. Sure, having more superchargers would solve the issue, but at this point they are still not on my way up north. These heaters are very efficient, and can run almost 24 hours on 1 gallon of diesel. So for me, in the winter I have the choice of burning 20 gallons of diesel to use my truck, burning half a gallon or less of diesel with this device in my Tesla, or burning nothing but freezing my a$$ off and foggy windows without it. I recently read an article in InsideEV of someone doing this in their Mitsubishi EV. I think for a select few like my self, this is a worthy feature. To experiment I am trying to make this a modular/removable system (the footwell in the back trunk) so I don't void my tesla warranty. Just need to find a way to run the exhaust out of the car. Anyone else try this on their Tesla Model S yet?
mknox
Well-Known Member
My sense is that the big hit comes from heating the battery, not the cabin. The battery is a big, broad sheet under the car that is constantly radiating any internal heat to the atmosphere.
I'm writing this with a bit of remorse, as I do not advocate the direction of this thread. That aside:
one feature of trucks - both semis and pickups - that run to/from the Arctic Ocean midwinter is to have insulation on every bit of exposed undercarriage items they can, and most especially their fuel tanks. Even though they are, of course, running diesel #1, and even though a constantly running diesel returns excess, engine-warmed diesel back to the tank, thus heating the remaining fuel, it is cheap protection to insulate that tank.
The analogous protection would be to insulate the Tesla's exposed battery bank. Someone wishing to go this route might consider affixing velcro "A" as perimeter strips on the battery case, plus a few in the middle, and "B" along an appropriately-sized patch of the kind of aluminized bubble-wrap insulation you can buy for garage doors, etc. I have a superinsulation that is laminate foil-foam-foil that has better insulative qualities than that material, but it's back in AK and I don't recall its name.
one feature of trucks - both semis and pickups - that run to/from the Arctic Ocean midwinter is to have insulation on every bit of exposed undercarriage items they can, and most especially their fuel tanks. Even though they are, of course, running diesel #1, and even though a constantly running diesel returns excess, engine-warmed diesel back to the tank, thus heating the remaining fuel, it is cheap protection to insulate that tank.
The analogous protection would be to insulate the Tesla's exposed battery bank. Someone wishing to go this route might consider affixing velcro "A" as perimeter strips on the battery case, plus a few in the middle, and "B" along an appropriately-sized patch of the kind of aluminized bubble-wrap insulation you can buy for garage doors, etc. I have a superinsulation that is laminate foil-foam-foil that has better insulative qualities than that material, but it's back in AK and I don't recall its name.
glhs272
Unnamed plug faced villian
No doubt the battery takes a big chunk of energy. Not much you can do about that, short of installing a second hydronic heater in the battery coolant loop. However, I have found the cabin heat takes a large chunk of energy too. Obviously on these long road trips I have been preheating as much as possible. When I get going I switch to range mode (hoping this reduces battery heating after preheat). The battery heating message usually goes away anyway. Then the heat generated from driving maintains the heat in the battery (or so the theory goes). I have found that when I turn the cabin heat off the power meter zeros out (not sure if the power meter captures battery heater load), so it definitely captures cabin heating. The regen limit doesn't come on so either the drivetrain heat is adequate or the battery heater still comes on without any way of telling.
I guess to boil it down, to get from the Mauston, WI supercharger to my destination in Rhinelander, WI (177 miles) turning off the cabin heat makes the difference of making there vs. not making it. It gets really hairy past Stevens Point as there are no public charging options available (it's a charging desert in northern Wisconsin). When I make this run with heat turned off, I usually make it with about 6 to 8 miles of rated range remaining (0 to 12*F). I dress like I am going snowmobiling so I don't get too cold, but keeping the windows from fogging is usually the most difficult part.
On Tesla's supercharger map they are planning on a Wausau supercharger this year. So once that is running this would really make this whole system moot in that particular case. But there are situations where it still might help.
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You americans have never heard of sth thats called insulation? We in Germany do this with our houses. It is forbidden to not insulate if you are building a new house.
A new house here only needs 4MWh of heat in Winter. There are even some that dont need any heat at all in winter.
Insulating a Tesla would be very easy and energy saving. You dont need to cool in summer or heat in winter.
A new house here only needs 4MWh of heat in Winter.
There are even some that dont need any heat at all in winter.Insulating a Tesla would be very easy and energy saving. You dont need to cool in summer or heat in winter.
JRP3
Hyperactive Member
You can't really put 6 inches or more of insulation in a car, though I'm sure the insulation could be improved. You would still need heating and cooling, remember your house doesn't travel down the road at 75+ mph on a regular basis. Think massive wind chill.
@ JRP3 thank you......... thats right. 1cm of insulation would be already great.
http://www.u-wert.net/berechnung/u-wert-rechner/ Here you can put in your material parameters to calculate thermal transmittance but independent of distance travelled.
So you would also have to calculate how much air surface is flowing around your car within a second.
The glass is certainly the biggest problem. Does the Model S use waste heat for heating? Would be convenient.
http://www.u-wert.net/berechnung/u-wert-rechner/ Here you can put in your material parameters to calculate thermal transmittance but independent of distance travelled.
So you would also have to calculate how much air surface is flowing around your car within a second.
The glass is certainly the biggest problem. Does the Model S use waste heat for heating? Would be convenient.
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