Heat pump in new models?

[kltye]

I have a high-end heat pump that’s about 5 years old. I assure you it struggles below about 30 and kicks in the auxiliary heating. Below 20, it kicks in both auxiliary and emergency heating. They’re great for the southeastern US, but mid-Atlantic and north, they’re essentially heat pump assisted electric resistance heaters.

It sounds like you have an undersized model or an improper model to handle low temperatures.

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[Jimrpa]

It sounds like you have an undersized model or an improper model to handle low temperatures.

I’m not an HVAC pro. That’s my HVAC guy’s job ?

 

[Mirak]

I bought a home with a high-end AC with heat pump. Tried it one winter month, and was shocked when my electric bill went through the roof. At least where I live, and suspect much of the country, it is vastly more expensive to heat a home with electricity than with natural gas.

The obsession with heat pumps in EVs is kind of funny. It’s the impact of freezing temps on battery chemistry that drives the lion’s share of range loss in the winter months. Banking on a heat pump to fix that problem, especially when they get less and less useful the colder it gets, is just… dumb. It’s another part to break.

 

[Peugfan]

The obsession with heat pumps in EVs is kind of funny. It’s the impact of freezing temps on battery chemistry that drives the lion’s share of range loss in the winter months. Banking on a heat pump to fix that problem, especially when they get less and less useful the colder it gets, is just… dumb. It’s another part to break.

Yes, the key is to keep the battery cells at the optimum temperature as much as possible. I don't understand why I have to have this giant aluminum battery box which in the winter keeps shedding the heat I need to keep the cells up to optimum temperature or heat that I could use to warm the cabin. The battery box should be insulated on the bottom and sides. So the battery box is shedding heat and I am using kw's heat running the resistive heater in todays -7 to 0 deg F temperatures. Would insulating the battery box be a problem for summers in say Texas or Arizona? I just want a Mach E designed for colder climates.

 

[Hammered]

That's not a heat pump ... but I think the car already does that today.

A heat-pump is basically an air-conditioner with a reversing valve. For normal AC, the cool air blows inside and the warm air blows outside. The reversing valve flips that.

BUT (and this is where I think people get all over-hyped over heat-pumps) ... heat-pumps are only efficient in a limited range of temps. In freezing temps they don't work well enough to warm the cabin and you need some form of supplemental heating.

The temp range where heat pumps work well isn't particularly cold. And yes we lose range in cold temps ... but these are only mildly cold temps where you aren't losing that much range. When the temps get really cold ... and the range loss is more severe -- that's where heat pumps don't work well at all.

This is why I think people over-hype heat-pumps.

Tesla's don't _just_ have heat pumps but you'd think that's all they do when you read the hype. They use heat pumps ALONG WITH other methods of heating.

Heat pump can be used to pull heat from the motors as well. This is what tesla does. To boost the heat output it can run the motors in a less efficient power mode to boost up the heat they generate. This is where the octovalve truly shines. Without a heat pump there's no way to pull heat from the motors.

 

[Hammered]

Yes, the key is to keep the battery cells at the optimum temperature as much as possible. I don't understand why I have to have this giant aluminum battery box which in the winter keeps shedding the heat I need to keep the cells up to optimum temperature or heat that I could use to warm the cabin. The battery box should be insulated on the bottom and sides. So the battery box is shedding heat and I am using kw's heat running the resistive heater in todays -7 to 0 deg F temperatures. Would insulating the battery box be a problem for summers in say Texas or Arizona? I just want a Mach E designed for colder climates.

A more intelligent system could store heat in the battery. For instance when charging in winter w/ tesla's significantly higher temp threshold, the battery could be heated to 55c and then use some of that heat to maintain the cabin if routing determines it's feasible, else it could retain all of its heat for the journey.

 

[smoke20]

I bought a home with a high-end AC with heat pump. Tried it one winter month, and was shocked when my electric bill went through the roof. At least where I live, and suspect much of the country, it is vastly more expensive to heat a home with electricity than with natural gas.

The obsession with heat pumps in EVs is kind of funny. It’s the impact of freezing temps on battery chemistry that drives the lion’s share of range loss in the winter months. Banking on a heat pump to fix that problem, especially when they get less and less useful the colder it gets, is just… dumb. It’s another part to break.

Im right next door in MO and am having a different experience. I have a basic Carrier 5 ton HP. There are 2 ways to go with aux heat; electric strips or gas (aka dual fuel). Im on gas when the temps go under 30. Most in my neighborhood use electric strips....ouchie wawa....that will cost in this climate...even when the cost of electricity drops in winter while the cost of gas increases due to demand.

It would seem to me the MME would benefit from a basic HP.

 

[Mach1E]

That's not really accurate and hasn't been for a long time. It is a myth that's repeatedly perpetuated though. My buddy just replaced his furnace with an air-source heat pump and it only needs auxiliary heating when it drops below -13F.

The Tesla heat pump appears to work to ~0F based on independent testing. I don't think they've ever actually published any information on what the specs are.

It may “work” at those temps, but does it work efficiently?

Based on multiple cold weather tests,
the Teslas with heat pumps seem to lose just as much range in the cold as the Mach E does.

It still seems like the heat pump efficiency advantage would happen in mild temps.

 

[Schox]

Based on multiple cold weather tests,
the Teslas with heat pumps seem to lose just as much range in the cold as the Mach E does.

Tesla Model Y LR Dual motor: WLTP 507 km/16,9 kWh - Tested winter range 451 km (-11,05 %)
Ford Mustang Mach-E 4WD: WLTP 540 km - Tested winter range 430 km (−20,37 %)
(MME RWD had a winter loss of −17,70 %)
BMW iX3: WLTP 450 km - Tested winter range 432 km (−4,0 %)

Does not seem like just as much... (But models without heat pump generally have a higer loss than the MME - heat pump is not a magic bullet, but the right pump implemented the right way helps in winter range, also here above the arctic circle.)

It doesn't have to have a efficiency of 7x in -30°C - it helps with efficiency of 2x (anything above 1x).
But I believe the lacking heat pump is the reason we have a relatively spacious frunk, despite Fords excessive plumbing upfront...

 

[SFC]

It may “work” at those temps, but does it work efficiently?

Based on multiple cold weather tests,
the Teslas with heat pumps seem to lose just as much range in the cold as the Mach E does.

It still seems like the heat pump efficiency advantage would happen in mild temps.

Yes, 0 degrees in the Tesla is where it starts losing efficiency, same with my buddy's furnace at -14. At that point an auxiliary resistance heater kicks in as the efficiency drops and can no longer keep up.

Trying to compare two completely different MFGs is a fool's errand. Ideally you would test power draw of the circuit of the heating element, assuming it was isolated. Short of that option, the best-case test you can do is a car pre and post heatpump (mach-e to mach-e or tesla to tesla). In the case of Tesla it was a fairly massive difference:

https://www.autoevolution.com/news/...er-heat-pump-vs-resistive-heating-208978.html

If Ford did the same, I'm hoping someone in the UK will measure a pre and post heatpump car.

 

[Mach1E]

Tesla Model Y LR Dual motor: WLTP 507 km/16,9 kWh - Tested winter range 451 km (-11,05 %)
Ford Mustang Mach-E 4WD: WLTP 540 km - Tested winter range 430 km (−20,37 %)
(MME RWD had a winter loss of −17,70 %)
BMW iX3: WLTP 450 km - Tested winter range 432 km (−4,0 %)

Does not seem like just as much... (But models without heat pump generally have a higer loss than the MME - heat pump is not a magic bullet, but the right pump implemented the right way helps in winter range, also here above the arctic circle.)

It doesn't have to have a efficiency of 7x in -30°C - it helps with efficiency of 2x (anything above 1x).
But I believe the lacking heat pump is the reason we have a relatively spacious frunk, despite Fords excessive plumbing upfront...

Can’t compare the WLTP or EPA as a baseline.

Gotta look at the real world warm tests (same driving loop) to real world cold tests.

 

[Mach1E]

Yes, 0 degrees in the Tesla is where it starts losing efficiency, same with my buddy's furnace at -14. At that point an auxiliary resistance heater kicks in as the efficiency drops and can no longer keep up.

Trying to compare two completely different MFGs is a fool's errand. Ideally you would test power draw of the circuit of the heating element, assuming it was isolated. Short of that option, the best-case test you can do is a car pre and post heatpump (mach-e to mach-e or tesla to tesla). In the case of Tesla it was a fairly massive difference:

https://www.autoevolution.com/news/...er-heat-pump-vs-resistive-heating-208978.html

If Ford did the same, I'm hoping someone in the UK will measure a pre and post heatpump car.

Didn’t Tesla offer the Model 3 at some point with and without a heat pump? That should be a super easy comparison.

I’ve seen tests where Tesla supposedly loses less range in the winter, but in the same test the Mach e has more overall range than the model Y in the cold.

It’s hard to tell what to believe because there are too many variables. Preconditioning and just a little wind change can make a huge difference.

 

[TheVirtualTim]

Heat pump can be used to pull heat from the motors as well. This is what tesla does. To boost the heat output it can run the motors in a less efficient power mode to boost up the heat they generate. This is where the octovalve truly shines. Without a heat pump there's no way to pull heat from the motors.

Tesla has multiple strategies which include the heat pump, scavenging heat from motors, and also using resistive heat.

 

[Hammered]

Tesla has multiple strategies which include the heat pump, scavenging heat from motors, and also using resistive heat.

Some models have a 1kW 12v powered 'hair dryer' type device unlike MME which must first heat a gallon or so of coolant before the cabin sees any heat. Ford should just pay telsa for the use of their patented system as it's light years ahead of what they've got, or can do for that matter cuz patents.

 

[awp0]

Tesla Model Y LR Dual motor: WLTP 507 km/16,9 kWh - Tested winter range 451 km (-11,05 %)
Ford Mustang Mach-E 4WD: WLTP 540 km - Tested winter range 430 km (−20,37 %)
(MME RWD had a winter loss of −17,70 %)
BMW iX3: WLTP 450 km - Tested winter range 432 km (−4,0 %)

Does not seem like just as much... (But models without heat pump generally have a higer loss than the MME - heat pump is not a magic bullet, but the right pump implemented the right way helps in winter range, also here above the arctic circle.)

It doesn't have to have a efficiency of 7x in -30°C - it helps with efficiency of 2x (anything above 1x).
But I believe the lacking heat pump is the reason we have a relatively spacious frunk, despite Fords excessive plumbing upfront...

I mean, we can pick and choose whatever tests we want to make a point. This one is a little less favorable toward the MY in cold weather:
https://www.macheforum.com/site/threads/cr-report-on-ev-range-tests.20961/post-494312

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