So I have to take a road trip in an EV, and it’s winter. So I’m going to have to use the AC. I know in my old ICE car I could have the AC off and the fan would blow hot air just from the engine. With my EV it seems to be the same, even with the AC button off the vents are blowing hot air. Is that hot air just heat vented from the battery? Or is it still using battery power for the compressor to heat the air.
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So when you are heating or defrosting a car, you have two choices. Outside air, or Recirculate.
Recirculate means you are keeping the air in the cabin instead of taking in new air and pushing the old air outside. Don’t worry, you still get some air exchange. On an EV, recirc is important so you aren’t throwing overboard air you spent battery to heat. On a gas car, recirc is less important since heat is free.
However, recirc has a problem: your breath and perspiration and wet clothing are adding water to the air, and when you recirc, the humidity gets higher and higher. Hot air can hold more water than cold air, so when it hits the cold windows, they fog or frost.
The cure for that is to run the air conditioner (i.e. normal A/C mode). The cooling element is before the heating element in the heating ducts, so this acts as a dehumidifier, chilling the air, removing humidity, then re-heating the air. Obviously, running the A/C when it’s below freezing outside is “pumping downhill”, so it’s rather efficient. It also provides a source for the heating you do next. That’s why some cars have separate A/C evaporators and heat pump condensers in the ducting.
When water evaporates, it cools you. That’s what sweating and wind chill are all about. When water condenses, you get heat. You gain about 300 watt-hours for every pound of water you condense. And this water evaporating in your lungs, skin and clothes was chilling you, making you want cabin heat, so the dehumidification of the cabin earns that heat back. That’s why it’s nice to recirc and dehumidify instead of tossing that moist air overboard as you might do in an ICE.
Why would you make a post like this and not mention what kind of EV you have?
I love my instant on heat pump.
Many now have a heat pump, similar to the AC but it can reverse the refrigerant flow and either cool the air coming in the car, expelling hot air by the radiator or heat the air coming into the car and blow cold air outside.
Older EV mostly had electric heaters, cheap and simply just like a plug in heater at home. But the can take 3-5 times more power.
Our Ioniq 5 mainly uses the heat pump, except for when running defrost then it uses both. Once the car has warmed up it can take just 0.8 - 1 kw to maintain the temperature. So with a 100% charge and 74kwh of battery capacity you can assume it would run over 70 hours.
Can you heat up the car with the phone app? That is a feature I really like with Tesla and was curious if Hyundai does it.
If your ioniq is anything like my old Niro, you actually have 2 condensers, and it can pull both heat and a from the heat pump at the same time.
That also means if you have a leak in one, you lose both. That’s how I found out about the setup.
I haven’t looked to see how the ev6 or ioniq 5 are configured though, but I’d expect it was the same as the niro
Set the temp leave it in full auto. The car knows when to run and not run the compressor or anything else based on temps. Just because then AC mode is on doesn’t mean the car is running it full bore when it’s below freezing. No you’re not hurting anything.
Some scavenge heat from the motors and batteries, probably not happening that much in winter. All have at least a resistive heating element as far as I can tell. The newer ones usually have/can be optioned to have a heat pump.
It really depends on your model. The BMW i3 for instance has a heat pump and a resistance heater, but the range extender version only gets the resistance heater.
EVs are very efficient. This means they don’t have all this waste heat sloshing around as in an ICE.
On the down side this means an EV has to get some energy from teh battery to supply heating (but compared to the amount of energy you use for driving the energy for AC/Heating is tiny)
On the up side this means you get heat/cold instantly and don’t have to wait for a motor to heat up. It also means you can precool/preheat your car from the app and you neve have to fiddle around with AC/heater controls while driving.
There are 3 ways to heat an EV. In order of simplest & most energy consuming to most complex t & least energy consuming:
( • resistance seat heater ) • resistance heater • heat pump external only • heat pump external & internal
Resistance heater = simple stick, run a current through it = heat. Efficiency = 100%. You need ~4kW of heat to heat up the interior, battery, etc. This costs ~4kW
Heat pump external = AC pump in reverse, pumps outside heat to the interior. Efficiency =100-400%. 4kW of heat now costs 1kW at best and 4kW when it’s colder than -15C.
Heat pump internal & external = same as the external, but more complex. This also scavenges heat from motors, electronics, pumps, battery pack and so on. Works more efficiently & more efficient in cold weather.
How would I be able to check which my car has? It’s a 2023 fiat 500e 3+1
Amazing that you asked a technical question but yet you didn’t tell us the name and the model of your EV. I suspect something is wrong here. Perhaps even a BS question…
Why assume it’s a “BS” question?
Unless you’re an EV nerd like most of us here, it’s pretty natural to assume all EVs would have a similar system, just as (virtually) all gas cars have a similar heating system; they all have a heater core that engine coolant gets diverted to, and a fan to blow the heated air into in the cabin. The heater in a 2023 Toyota Corolla isn’t really that different than one in a 1957 Chevy.
The fact that EVs use a few different systems (or a combination of them) really shows how early in the transition we are- manufacturers haven’t really settled on one “best practice” yet.
Yes, they have a patent on that, they describe it as intentionally using the motor inefficiently.
I wonder if they can use that and the heat pump for dynamic brakes. (Regen but without the ability to put it in the battery, because it’s full).
I just saw a video from Tesla on their heat pump for cabin heating. As always, they found a way to reduce the number of parts while making the device more efficient. They have some good engineers on staff!
I have been considering a Ford E transit, and wonder how the heating is in that vehicle? Did they just cheap out and use a resistive heater ? If so, that would sure cut the range in the winter. I would have to consider bringing along a portable power pack in the back of the van and run a resistance room heater instead.
Energy from the battery is used to heat the air, be it with a heat pump or resistive heating. EVs are very efficient and don’t produce a lot of waste heat (comparatively) as a byproduct of driving.
Teslas use a combination of energy transfer via heat pump from motor heating, and PTC heater (the defrost heat). Up to 15kW can be consumed for rapid heating of cabin, rear window and windshield. It’s awesome.
In any case, whether you’re driving an ICE car or EV, you should be leaving the AC on auto. The air conditioning compressor will dehumidify the air, reducing fogging up in the winter. Even when it’s -40 degrees out.