Electric car heat! Liquid?

[jamesqf]

I think you've run into one of the basic problems with electric cars in cold weather. With an IC engine, you have a LOT of waste heat: even the Insight burns something like a gallon of gas per hour, the Geo maybe double that, and about 1/3 of that heat goes into the cooling system. All that waste heat makes it practical to keep the passenger compartment at a comfortable temperature, even though it's separated from the outside only by a thin skin of metal & glass.

The only solution I can think of is to use one of the kerosene/propane catalytic heaters, of course checking first for things like carbon monoxide, and whether they're safe in a small enclosure.

[bennelson]

Let's be clear here.

I am NOT trying to get the entire car to 70℉ or more. Mostly what I am trying to do is figure a way to bring some heat with me from my wall outlet through a means other than a 12V battery, which is itself suffering from reduced voltage due to the cold.

I would like to design a system which can warm up the car ahead of time, and then bring some additional heat which can be run out the defroster onto the windshield to keep it from fogging up.

I would imagine that pre-heating some amount of liquid - water, anti-freeze, mineral oil, etc, and then running it through the heater core would give me some heat for a while. I am guessing it wouldn't be a ton of heat and not for too long. I would depend on the type and amount of transfer liquid.

I could then also have a secondary heating element (or possibly the same one, just wired different) which would take power from either my main 72V battery pack, or a secondary 12V battery, which could continue to heat the liquid medium while I am on the road.

Of course all the specifics here have to be worked out. That's why I am tinkering with this, seeing what works, and what doesn't.

I already am wearing warm clothing. I am really not too cold from driving. Mostly defogging is the issue, as a safety concern about being able to see the road.

[IndyIan]

Originally Posted by MazdaMatt

He isn't just bringing a 2gal jug of hot water with him... he'll be running 2gal of hot water through the heat exchanger while keeping it hot, thereby warming the entire car... which WILL hold its heat for a while.

Well, I'm pretty sure that you would use about the same amount of energy to move the car, as you would need to heat it to a similar level as a gasoline car... Now maybe you don't need to heat the car like a normal one, maybe 1/5 is enough to keep the window clear.

Try it out, on a really windy day, -10 C, bring a 1500W hair dryer into your car and turn it on with the interior fan on. If the temp ever gets above 0C inside the car I would be surprised. From a 72V battery, its a constant 20 amp drain. Now put the hair dryer on low and stick it down the front of your jacket, you will be sweating in 30 seconds.

I'm not trying to be negative but heating the whole interior is inefficient and expensive in a battery powered car, there are heated vests for motorbike riders that will keep your core warm and therefore your limbs for small fraction of the energy.

Ian

Doh, I'm a slow poster, as for the windshield, look into the anti fog stuff hockey players use for clear visors. And dehumidifying the car overnight might help, if the temps are near 0C. Also an old credit card works good for scraping the inside of the windows if your technology fails.

[TestDrive]

Originally Posted by bennelson

Mostly defogging is the issue, as a safety concern about being able to see the road.

When I was a youngster, the school buses often had a double pane add-on pasted (a bead of black - rubber looking material) to the inside of the windshield, driver's side window, and the window in the front entry door. Those add-ons aways stayed clear, even when the school bus defroster wasn't able to keep the rest of the windshield defogged.

I have no idea what to suggest for stick-um, but you might try experimenting with a piece of plexiglass.

[Big Dave]

I've been working with a local university on an electric service vehicle.

One would think this is an ideal application for an electric.

Truck is used ten hours per day. Truck never drives over 25 MPH.
Truck never drives more than seven miles a day. Truck spends most of work day parked. Perfect.

We got an old Grumman aluminum van. The electrical engineer speced out the electrical system so don't ask me about it. My only input was to insist on a TEFC propulsion motor.

The lack of heater is a killer. You have to have 120 degree supply air to defrost the windshield or the truck is a no-go. We tried various schemes for an electric heater and all of them killed the main batteries. What did work was a 12v propane heater. Now we arec working to tone down this miniature blast furnace.

Electric cars gotta have heaters or they are doomed to being niche vehicles.

[bennelson]

I talked to a guy a while back who drove a Citicar back when they were new. He put 200 miles a week on it for years.

He told me that he had some sort of internal combustion heater for it. It worked great, other than one of his legs was frozen, and the other was baked! The other problem is that combustion creates water vapor which is exactly what I DON'T WANT in the car.

I wouldn't want to use petroleum-based fuels for my car. Seems to defeat the point to drive an electric car if you just add gasoline to it to heat the thing!!! A bio-diesel heater could be a possibility...

Electric creates heat without adding moisture. The car's existing heater core and vents are designed to deliver heat where ever I want to direct it - mostly the windshield.

It just seems to me that it's logical to heat a liquid so that I can bring some electric heat with me, without having to create all that heat directly from my battery pack.

Of course the other way EVers usually add heat is to insert an electric resistive heating element (toaster guts!) in place of the original heater core. But that's far too traditional for me! Where's the fun in it!!?!?

[jamesqf]

You'd want to have the combustion separate from the interior air, with a heat exchanger (like the VW or aircraft heaters), so as to avoid carbon monoxide poisioning. (Which is a real risk: there was an article in the news about today about 3 women who died because they slept in their car at a local ski area, with the engine running.) So you arrange for a burner or catalytic heater, using vegetable oil if you want to be a purist, and direct the heat into the existing system. You might also consider adding insulation to the passenger compartment...

[captainslug]

If you want an absurdly more efficient option for producing heat in a closed loop, look into RV water heaters.
They start at 2.5 gallons and are available in propane or electric.

[Christ]

Is there anything on the car that already produces any kind of heat? It seems not...

I'm keeping an eye on this thread, as I feel something very interesting may come of it.

[NiHaoMike]

For defrost, what about cover the inside surface of the windshield with a thin layer of transparent conductive material and use that as a heating element? Maybe even use double layer glass to reduce power requirements? Probably not practical for DIY but should work nicely for production. For personal heating, what about heated seats and heated steering wheel?