RonDawg
Posts: 2656
Joined: Sat Jan 12, 2013 3:46 am
Delivery Date: 11 Jan 2013
Leaf Number: 027089
Location: SoCal

Re: Heat pumps in EVs

Sun Feb 05, 2017 5:37 pm

TomT wrote:The larger the battery, the less difference a heat pump makes...


Until you actually need the range that is no longer there, thanks to a power-hungry heater.

I guess GM hasn't learned all the lessons from the Leaf.
Blue Ocean 2012 Leaf SV, lost that 1st bar on 11/21/2015 at 26,435 miles.
Lease returned on 12/23/2015. Final LeafStat figures: 225 Gids, 17.44 kWH, SOC 91.89%, SOH 82.36%, 69.49% HX, 54.57 Ahr, battery temp 61.8 F
Now driving a 2015 VW eGolf SEL

LeftieBiker
Posts: 6810
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Heat pumps in EVs

Sun Feb 05, 2017 5:40 pm

I too will be test driving a Bolt next month, but assuming I haven't already picked up a 2016 Leaf at that point it still isn't extremely likely I'll lease one. Putting aftermarket cushions and seat covers on a $450 a month car (plus an aftermarket surround view system if the LT) just seems wrong. GM claims a motor heat recovery system that improves the resistance heater in the Bolt, but how much heat will the motor generate in 0F weather? I'm sure it will provide lots of waste heat when it's 90F outside... ;-(
2013 "Brilliant Silver" SV with Premium Package and no QC, and 2009 Vectrix VX-1 with 18 Leaf cells.

The most offensive, tasteless phrase in use here is "Pulled the trigger." I no longer respond to posts that use it.

SageBrush
Posts: 1114
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

Re: Heat pumps in EVs

Sun Feb 05, 2017 6:11 pm

webeleafowners wrote:I was surprised to find them not available in the Teslas. Curious as to why.
IIRC Tesla uses waste heat from the battery to heat the cabin. They have hinted at a novel system for the Model 3.
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California with 63.9 Ahr after 22k miles
Car is now enjoying an easy life in Colorado

RonDawg
Posts: 2656
Joined: Sat Jan 12, 2013 3:46 am
Delivery Date: 11 Jan 2013
Leaf Number: 027089
Location: SoCal

Re: Heat pumps in EVs

Sun Feb 05, 2017 6:19 pm

LeftieBiker wrote:I'm sure it will provide lots of waste heat when it's 90F outside... ;-(


I call it the "motorcycle heating system." Lots of heat when you don't want any, none when you're freezing your butt off.
Blue Ocean 2012 Leaf SV, lost that 1st bar on 11/21/2015 at 26,435 miles.
Lease returned on 12/23/2015. Final LeafStat figures: 225 Gids, 17.44 kWH, SOC 91.89%, SOH 82.36%, 69.49% HX, 54.57 Ahr, battery temp 61.8 F
Now driving a 2015 VW eGolf SEL

LeftieBiker
Posts: 6810
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Heat pumps in EVs

Sun Feb 05, 2017 7:28 pm

RonDawg wrote:
LeftieBiker wrote:I'm sure it will provide lots of waste heat when it's 90F outside... ;-(


I call it the "motorcycle heating system." Lots of heat when you don't want any, none when you're freezing your butt off.


That system is better, because even though your limbs and head freeze, it does actually provide heat in frigid weather, at least to your thighs. And, of course, you can always - carefully, avoiding the spark plugs! - warm your gloved hands while stopped.
2013 "Brilliant Silver" SV with Premium Package and no QC, and 2009 Vectrix VX-1 with 18 Leaf cells.

The most offensive, tasteless phrase in use here is "Pulled the trigger." I no longer respond to posts that use it.

GerryAZ
Gold Member
Posts: 1369
Joined: Mon Nov 22, 2010 6:47 pm
Delivery Date: 12 Jun 2011
Location: Phoenix, AZ

Re: Heat pumps in EVs

Sun Feb 05, 2017 7:47 pm

My experience leads me to conclude the real world difference in efficiency between the 2015 heat pump and 2011 A/C for cooling in Phoenix summer temperatures is minimal. Either unit cools the LEAF well with minimal impact on range, but the black interior of the 2015 does absorb more solar energy.

Gerry
Gerry
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015

arnis
Posts: 716
Joined: Sat Jan 23, 2016 3:21 pm
Delivery Date: 23 Jul 2014
Leaf Number: 015896
Location: Estonia, Europe

Re: Heat pumps in EVs

Mon Feb 06, 2017 5:37 am

GerryAZ wrote:Actually, the LEAF heat pump system (at least on 2015 model) has two heat exchangers in the duct work in the dash and can run one to heat the air while the other dehumidifies the air. Since I have had both 2011 with resistance heater and 2015 with heat pump, I can say that the heat pump is a great improvement in my climate.

Gerry


No. There are two heat exchangers but they never work simultaneously.
If HEAT and AC are both enabled (air drying in moist weather) compressor runs the AC (cooling, dehumidification) and PTC
heats the air after it has been dried. Aka it takes as much electricity as it takes on cars without heatpump.
Dehumidification is unnecessary and not possible in freezing weather. I've tried, doesn't work well enough.
Actually it is almost never needed. It is easier/more efficient to crank up the heat with heat-pump enabled vehicles.
Leaf with heat pump can generate 8-10kW of heat. That is more than enough to dry the windshield :D

Heat pump is not necessary if temperatures often drop down to 10C/50F and rarely drop below 4C/40F. Due to the fact that PTC
doesn't need a lot to heat the cabin moderately. Maybe this is why Bolt doesn't have it.
But near freezing the difference becomes bigger and bigger. Up to -10C/14F. 2-3x less consumption on heating.
Below -15C/ 5F heat pump is pointless. So it clearly depends on climate.
Estimations for warm Leaf cabin after warming up (w pump): 0C/32F - 300W, -5C/23F - 600W, -10C/14F - 1100W, -15C/5F - 2000W (PTC only).

Tesla doesn't have heat pump. Most likely the AC system is designed to be as powerful as possible in AC cycle. Because Tesla
does MAX out AC requirements in hot weather while SuperCharging. More is needed but that is not possible (no room for radiators).

I expect European version of Bolt and maybe even Model3 will be offered with reversible AC-system. It does make sense even more
if vehicle heats the battery to optimal temperature. Doing that at 200-400% efficiency saves on consumption while heating the pack.

Chevy tried very hard to keep the cost down. And, like I said, in warm climate, pump is not reasonable. Especially with 60kWh pack.
They will learn their mistake as soon as Canada or Europe starts to acknowledge Bolt as not 200mile EV on highway but rather 150 mile
EV for all year round use.

Driving for 3 hours in Bolt will draw 3x3kW=9kWh of heat in cold weather (14F). Aka 1/6th of the pack. At those temperatures heat pump makes sense.
Short range EVs <30kWh -- Medium range: 30-60kWh -- Long range: >60kWh
Charging: Trickle <3kW -- Normal 3-22kW -- Fast 50-100kW -- Supercharging >100kW

LeftieBiker
Posts: 6810
Joined: Wed May 22, 2013 3:17 am
Delivery Date: 31 May 2013
Location: Upstate New York, US

Re: Heat pumps in EVs

Mon Feb 06, 2017 6:18 am

Below -15C/ 5F heat pump is pointless. So it clearly depends on climate.


Many of us in the US have noticed that the heatpump stops helping range significantly below 15F. I don't dispute that it's still doing something below that, but it isn't helping range much at that point. I believe that 5F is where it stops working entirely.
2013 "Brilliant Silver" SV with Premium Package and no QC, and 2009 Vectrix VX-1 with 18 Leaf cells.

The most offensive, tasteless phrase in use here is "Pulled the trigger." I no longer respond to posts that use it.

SageBrush
Posts: 1114
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

Re: Heat pumps in EVs

Mon Feb 06, 2017 7:37 am

Heat pumps are fascinating devices.

In terms of efficiency, COP is the unit to use, meaning how many units of heat can be moved from one space to another using one unit of energy. A resistance heater has a COP of 1.0; a heat pump has a range from 1 - 5ish, depending mostly on the temperature of the source. Standard heat pumps working as heaters shine when the source temperature is about 45F or greater and are down to a COP of 1.0 when temperatures hit about 20F. The temperature range can be improved using different gases. E.g, the Japanese use CO2 in their residential pumps which IIRC returns a COP of 2.0 at 5F.

Toyota put a heat pump into the Prime for this newest model that includes gas re circulation. I think that temperature performance rivals that of a CO2 pump.

Personally -- I don't really care much if my car has a heat pump or not because the heated seats work so well in conjunction with gloves and warm shoes and are low power devices.
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California with 63.9 Ahr after 22k miles
Car is now enjoying an easy life in Colorado

SageBrush
Posts: 1114
Joined: Sun Mar 06, 2011 2:28 am
Delivery Date: 13 Feb 2017
Location: Colorado

Re: Heat pumps in EVs

Mon Feb 06, 2017 7:49 am

LeftieBiker wrote:GM claims a motor heat recovery system that improves the resistance heater in the Bolt,(

IIRC motors are about 97% efficient, so at 10 - 20 kW operation about 300 - 600 watts of waste heat are available for recovery.

That sounds like it might work nicely for a long road trip if the car is pre-heated, but I have no idea how well GM implemented the idea.
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California with 63.9 Ahr after 22k miles
Car is now enjoying an easy life in Colorado

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