AAA confirms what Tesla, BMW, Nissan electric car owners suspected — cold weather saps EV range

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LeftieBiker said:
Most of the new EVs sold today would do just fine in bitter cold with average commutes and letting the driver do whatever (s)he wants to do with heating settings.

Except for the ones who acquired their EV with range needs that approach the EPA range rating of the car. They, never having been told by the sales "people" about Winter range drop, are essentially screwed.

He said "with average commutes". The average commute is about 30 miles round-trip. There are no modern BEVs with an EPA range anywhere near that low.
 
Private vehicle is ~25 miles mean average round trip according to 2017 NHTS. Would guess the not reported median is closer to 20 miles round trip.
 
Can anyone here comment on the heating efficiency of EV heat pumps? Are they rated as residential heat pumps are, eg. HSPF?

Ok, found this thread but not updated recently:
http://www.mynissanleaf.com/viewtopic.php?t=15108

Looking for manufacturer specs on EV heat pumps or someone who has appropriately tested this on one's own.
 
iPlug said:
Looking for manufacturer specs on EV heat pumps or someone who has appropriately tested this on one's own.
I've looked without much success but you can pull up efficiency curves of different heat pumps that then give you a pretty good idea. The air to air pumps come in a couple of flavors:
1. By refrigerant
2. Vapor recirc (the Prius Prime e.g)
3. Variable Power. IIRC so-called inverter controlled are the best since they have what I call infinite gearing by analogy.
 
SageBrush said:
iPlug said:
Looking for manufacturer specs on EV heat pumps or someone who has appropriately tested this on one's own.
I've looked without much success but you can pull up efficiency curves of different heat pumps that then give you a pretty good idea. The air to air pumps come in a couple of flavors:
1. By refrigerant
2. Vapor recirc (the Prius Prime e.g)
3. Variable Power. IIRC so-called inverter controlled are the best since they have what I call infinite gearing by analogy.
I’m having a hard time finding the efficiency curves of plug-in vehicle heat pumps. Able to find residential ones.

IIRC, Prime has one of the most efficient heat pumps in the plug-in vehicle market. Toyota says the heat pump in the Prime uses 63% less energy than conventional resistive heating and claims extend driving range up to 21%.

https://www.sae.org/news/2017/04/inner-secrets-of-the-toyota-denso-heat-pump-revealed

I would presume the 63% is best yield achieved on an efficiency curve. By comparison our residential heat pump is HSPF 13.0 = 3.81 COP.

Someone can check my math, but that is a best case scenario 74% less energy than conventional resistive heating. So the Prime heat pump still has room for improvement compared to some of its stationary peers.

Of course, without ambient temperature efficiency curves to compare, we don’t know how well a plug-in vehicle heat pump is doing at say 0-20°F when heating demand would be highest and effiency the poorest.
 
Perhaps I was not clear -- you do not have to find a heat pump in a car, just match the engineering categories I mentioned earlier.
 
I may not be completely understanding your position, and you may know substantially more about heat pumps. I was looking for hard specification numbers.

I would also suspect that by knowing the refrigerant type, if it has vapor recirculation tech like the Prime, and if it is single stage/dual stage/infinitely variable speed powered, etc. that this will give you some ballpark comparative ideas of efficiency, at least relative rankings.

Definitely an amateur on my end regarding heat pump systems, but can we say that if a fixed/residential heat pump system and plug-in vehicle heat pump system have the same refrigerant, recirculation tech, variable speed features, etc. and we know the HSPF/COP/efficiency curves of that residential unit, that the plug-in vehicle heat pump system therefore has identical efficiency specs?

My guess would be probably not off tremendously, but to get a heat pump system into a vehicle requires miniaturization/component engineering compromises and placement of components in perhaps suboptimal locations thus reducing efficiency, no?
 
The reason that most heatpump-equipped EVs have lower efficiency than a residential unit is that EVs,unlike houses, have to be heated quite a lot in a matter of minutes - or even a single minute - while units heating houses can take a little longer without complaints. So EVs use their resistance heating units (which are a backup only with residential units, IIRC) to speed up heating the cabin. The resistance heaters then shut down after the cabin has gotten warm enough for the heat pump to maintain the set temp. That's why we call the system in the Leaf a "hybrid" heating system: both heating units work together, speeding heating but lowering efficiency. The Prime appears to use a heatpump only, putting a definite lower temp limit on its usefulness, albeit with much lower energy consumption.
 
iPlug said:
but can we say that if a fixed/residential heat pump system and plug-in vehicle heat pump system have the same refrigerant, recirculation tech, variable speed features, etc. and we know the HSPF/COP/efficiency curves of that residential unit, that the plug-in vehicle heat pump system therefore has identical efficiency specs?

No one would confuse me with a heat pump expert but the above is my understanding. Ballpark anyway
 
iPlug said:
but can we say that if a fixed/residential heat pump system and plug-in vehicle heat pump system have the same refrigerant, recirculation tech, variable speed features, etc. and we know the HSPF/COP/efficiency curves of that residential unit, that the plug-in vehicle heat pump system therefore has identical efficiency specs?

No one would confuse me with a heat pump expert but the above is my understanding. Ballpark anyway
 
LeftieBiker said:
The reason that even the Prime has lower efficiency than a residential unit is that EVs,unlike houses, have to be heated quite a lot in a matter of minutes - or even a single minute - while units heating houses can take a little longer without complaints. So EVs use their resistance heating units (which are a backup only with residential units, IIRC) to speed up heating the cabin. The resistance heaters then shut down after the cabin has gotten warm enough for the heat pump to maintain the set temp. That's why we call the system in the Leaf a "hybrid" heating system: both heating units work together, speeding heating but lowering efficiency.
A heat pump can work "faster," (meaning transfer more heat/time) but at reduced efficiency
 
I just came here to correct what I wrote earlier: as far as I can tell the Prime doesn't have a resistance heater - it gets cabin heat from the heat pump at more moderate temps, and they assume you'll be running the ICE at temps below the mid teens F. That makes for a very efficient heater, but one with a definite lower temp limit on its usefulness.
 
LeftieBiker said:
...... as far as I can tell the Prime doesn't have a resistance heater - it gets cabin heat from the heat pump at more moderate temps, and they assume you'll be running the ICE at temps below the mid teens F. That makes for a very efficient heater, but one with a definite lower temp limit on its usefulness.
Interesting, not sure I like that :(
In my climate we can goes days below zero, weeks + in the low teens and single digits, so it sounds like the Prime wouldn't give us any heat in those cases, unless the ICE ran? If this is the case the Prime loses some of its charm for us as I'd prefer a vehicle we could run EV in all temps(and get heat) albeit at a much-reduced range. Reminds me of a Volt and plug-in Ford C-max we tried in a cold winter day 5 years ago, neither ever shut off the ICE due to cold temps, at that point we tried the Leaf and it had nice heat, even in the single digits(we later bought the Leaf). Personally if it's true the Prime doesn't have a resistive type of heater I think it's a mistake, some EV range is better than none :)
 
I asn't able to get a definitive answer from my reading on this - just a lack of any mention of a resistance heater. There doesn't seem to be one integrated into the heatpump, either, as I looked at the schematic for that, too. Others should look into it as well, and ask at dealerships. (caveat emptor there!) And yes, it does suck terribly if there is no resistive heater. Our PIP has no electric heat of any kind, and no heated steering wheel, so I drive it only rarely in Winter, and often have to wear my electric heated gloves when I do. I don't know why they just didn't add a little resistance heater to the heat pump on the heat side. Maybe it's because it's actually made by Denso, IIRC, and they didn't want to do it.
 
NO resistance heater. I downloaded and searched the owner's manual. Here is the relevant section:

...

Crap. I can't get $#@!@ windows to copy and paste this as plain text, even after pasting the PDF copy into Open Office and saving it as plain text. I'll work on this later. It's section 4946-1 in the manual. Here is a SHORT, manually typed quote:

"When the outside temperature is low or it is snowing, (!!!?) compared to conventional vehicles, heating may be less effective and warm air may not come out." Yikes. I added the parenthetical part.
 
Appreciate the input of all.

We have a PiP as well. It is neither cold enough here nor does the PiP have long enough EV range for us to need resistive or heat pump heat. Seat heaters are fine during the short EV interval getting me to and from my 7 mile round trip work commute. If in the car long enough and it's cold enough, EV range is already depleted and on the ICE comes and behold ICE heat.

Feeling bad for the rest of youse guys up in the northeastern parts. Technology has a way to go up in those parts.

Even home heat pump works great here and never need resistive backup except for a few minutes a year to keep the heat on while the defrost/de-ice coil cycle momentarily runs on the coldest pre-dawn mornings.
 
LeftieBiker said:
"When the outside temperature is low or it is snowing, (!!!?) compared to conventional vehicles, heating may be less effective and warm air may not come out." Yikes. I added the parenthetical part.
I owned the Prius Prime for about a year in Colorado. Heating was fine.
 
SageBrush said:
LeftieBiker said:
"When the outside temperature is low or it is snowing, (!!!?) compared to conventional vehicles, heating may be less effective and warm air may not come out." Yikes. I added the parenthetical part.
I owned the Prius Prime for about a year in Colorado. Heating was fine.

Were you able to run it in EV mode without engine starts, in sub-20F weather? I'm guessing that the hills forced regular ICE starts...?
 
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