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Old 06-05-2009, 03:19 PM   #1
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Hybrid and Electric Cars... Heat and AC?

My first car was a 1974 4-door Chevy Nova and the heater vents would melt a bic pen. Neither here nor there, but a friend asked me about hybrid heat and AC, and I know you're all a bunch of vehicle nuts with more than a few owners too:

Lets start with a pure electric car... how does the AC work? If it's a compressor, how much does it impact operational hours?

Now... how does the heater work? 100% battery operated would seem like the heater would be a giant toaster, which is hugely inefficient. I suppose you could use the heat that the batteries generate as they discharge, but that seems inefficient or ineffectual... or at the very least I would think you wouldn't want to have batteries that got hot enough to heat the cabin.

Which brings us to the consideration of the hybrid vehicle. My guess would be that the gasoline engine also runs the AC, which doesn't impact the range/mileage nearly as much because the engine duty is not directly related to the operation of the vehicle... e.g. when running the AC compressor you're not charging as much, but does it really work that way, and how does that affect the mileage? What is the effect on a 50mpg Prius when the air is on? Do you lose the same single digit mpg you might from a gasser, or is it more like 20mpg?

To round it out, how is heat handled in the hybrids? Does the motor put off as much extra heat as traditional engine?

Lastly I know there are a handful of Prius owners and at least one fully electric on the board, what is the real world experience with how the heat and air conditioning work and affect mileage?
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Old 06-05-2009, 11:00 PM   #2
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Re: Hybrid and Electric Cars... Heat and AC?

OK....where do I start....

First, for both Hybrid (most) and Electric vehicles the AC is electric. This eleminates the need to have a belt driven compressor.

Yes, the electric AC does potentially impact the SOC of the batteries.
Example: today a couple of times I was in our Prius and my wife needed to run in some place for an errand.... she left me and my healing knee in the Prius. WITH that AC On. The ICE is NOT running..... until the Battery SOC reaches a point where the ICE will start up and charge the battery and then shut off again.

For Electric vehicles the AC is often an electric heat-pump.

For heat Hybrids still use engine coolant. THis means that in colder weather you may get less fuel economy as the ICE runs more to be able to continue to provide heat. The Prius is supposed to have some resistance heating coles for when LOTS of heat is needed in a really short period of time... BUT we have yet to have an occasion where we could tell that it was engaged.

For electric vehicles' heat, the heat pump is still in play. BUT some (like my S10-EV) also have other types of furnaces similar to the fuel furnaces available for SMBs.

I cannot say that I have seen an EV that has purely resistance heating. I have seen EVs with NO heater. The SOC of the batteries is just too important for the speed and drive distance for the EV folks to let a heater have too much impact.
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Old 06-06-2009, 05:07 PM   #3
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Re: Hybrid and Electric Cars... Heat and AC?

We have had our Prius for over 5 years now and are considering a new one. To be honest I don't really pay that much attention to the milage to document any difference the A/C or heater makes. Living in Northern California the A/C is on 95% of the time as driving with the windows down makes these vehicles very un-aerodynamic. We have long since stopped driving like a Prius owner should (conserving every last ounce of gasoline) and drive it like any other vehicle. I.e. 70 mph where we can, etc. Our milage is 52 on the Freeway (that is if you can call them freeways anymore in California) and 46 around town. By far the biggest reason I bought it was the low emissions. That little PZEV sticker that allows me single occupant access to the HOV lanes is priceless.
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Old 06-06-2009, 09:44 PM   #4
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Re: Hybrid and Electric Cars... Heat and AC?

Quote:
Originally Posted by charlie56
We have had our Prius for over 5 years now and are considering a new one. To be honest I don't really pay that much attention to the milage to document any difference the A/C or heater makes. Living in Northern California the A/C is on 95% of the time as driving with the windows down makes these vehicles very un-aerodynamic. We have long since stopped driving like a Prius owner should (conserving every last ounce of gasoline) and drive it like any other vehicle. I.e. 70 mph where we can, etc. Our milage is 52 on the Freeway (that is if you can call them freeways anymore in California) and 46 around town. By far the biggest reason I bought it was the low emissions. That little PZEV sticker that allows me single occupant access to the HOV lanes is priceless.


Charlie, that is the best part of the Prius..... you can drive it for major fuel economy if you want, or you can drivet it just like any other car and still get fuel economy better than any other car. What other 4 door car that can carry 4 adults comfortably will get 46mpg around town and 52 on the highway?
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2013 Jeep Wrangler Unlimited Rubicon (15 to 18 mpg) [Johnnie]
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