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Heat Pump and Non Heat Pump Discussion

35408 Views 32 Replies 18 Participants Last post by Jim Matthews, 7 mo ago

jongodfrey

Discussion Starter · Jul 14, 2021

Hidden in a couple of threads there has been lots of discussion about Heat Pumps. I completely get the desire or even need for a HP in cold climates but in temperate climates like South West UK it's less easy to justify the cost.

One or two comments have suggested that one key function of the HP is to heat the battery as well as reducing energy used to heat the cabin. This might well be true but this doesn't mean the Non-HP models don't have battery heaters for this purpose. I found this article which is very interesting so thought I would share.

Q. The E-GMP is equipped with an electric heating system to maintain battery performance in winter. What kind of technology is this?

Choi Yong-Hwan | In the Li-ion batteries used in BEVs, cycles of ‘charging’ and ‘discharging’ are repeated as lithium ions move back and forth between the positive and negative electrodes through liquid electrolytes. The reduction in the battery output happens in winter because electrolytes in a liquid state harden at lower temperatures. Hardened electrolytes cause the movement of lithium ions to slow down, which in turn increases the internal resistance of the battery, resulting in a decrease in the charge/discharge performance. For this reason, charging the battery in winter takes longer than charging at room temperature.

To solve the problem, a heater technology that forcibly raises the temperature of the battery has been utilized in the E-GMP. By instantly raising the temperature of the battery, electrolytes can be kept at room temperature, which enables smoother charging of the battery even at low temperatures. When you experience an E-GMP-powered EV in winter, you will discover that any inconvenience caused by delayed battery charging time has been further eliminated.

Source: Interview with Researchers The Story of EV Technology on E-GMP - Hyundai Motor Group TECH

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Bill Schaeffer

· #2 · Jul 14, 2021 (Edited)

Thanks for this post Jon. It's something that I hadn't completely appreciated - even though it is mentioned on a number of videos.

The Heat Pump isn't so much about performance of the car in the cold as it is about reducing the time you need to wait whilst your car charges up.

Most of us will charge overnight at home, where charging speed is fairly irrelevant. But where the HP really becomes a bonus is when you charge at a charging point - pre-heating the battery will allow us to achieve those quoted 0-80% times. With a colder battery you might be waiting longer.

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jongodfrey

Discussion Starter · #3 · Jul 14, 2021

Bill Schaeffer said:
Thanks for this post Jon. It's something that I hadn't completely appreciated - even though it is mentioned on a number of videos.

The Heat Pump isn't so much about performance of the car in the cold as it is about reducing the time you need to wait whilst your car charges up.

Most of us will charge overnight at home, where charging speed is fairly irrelevant. But where the HP really becomes a bonus is when you charge at a charging point - pre-heating the battery will allow us to achieve those quoted 0-80% times. With a colder battery you might be waiting longer.

Really sorry, Bill, but I don't think that is true.

It works like this. There is an optimum temperature for the battery to charge at. If it's too cold or too warm it affects internal resistance and therefore charging. The battary is managed by the battery management system. If it's too hot the coolant system will cool it using the small radiators. If it's too cold it needs heating. Heating can come from either an Inductive Heater OR a Heat Pump. Inductive Heater use more energy but if you are charging it's power from the charger anyway. You'd get increased "losses" as part of the charge.

Where the Heat Pump helps is with RANGE is where the vehicle (Cabin, Battery or anything else) needs heating from the Battery. So if you are in a cold climate you would waste energy that can be used otherwise for range by heating the car.

So I suggest, but happy to be proved wrong; Heat Pump and Non-Heap Pump cars will charge at the same rate. Heap Pump cars will convert more of the charge into usable energy when charging in very cold conditions. Heap Pump cars will use less energy to heat the cabin in cold weather and will therefore have a longer range.

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Bill Schaeffer

· #4 · Jul 14, 2021

jongodfrey said:
Really sorry, Bill, but I don't think that is true.

It works like this. There is an optimum temperature for the battery to charge at. If it's too cold or too warm it affects internal resistance and therefore charging. The battary is managed by the battery management system. If it's too hot the coolant system will cool it using the small radiators. If it's too cold it needs heating. Heating can come from either an Inductive Heater OR a Heat Pump. Inductive Heater use more energy but if you are charging it's power from the charger anyway. You'd get increased "losses" as part of the charge.

Where the Heat Pump helps is with RANGE is where the vehicle (Cabin, Battery or anything else) needs heating from the Battery. So if you are in a cold climate you would waste energy that can be used otherwise for range by heating the car.

So I suggest, but happy to be proved wrong; Heat Pump and Non-Heap Pump cars will charge at the same rate. Heap Pump cars will convert more of the charge into usable energy when charging in very cold conditions. Heap Pump cars will use less energy to heat the cabin in cold weather and will therefore have a longer range.

I am very happy to state that you absolutely know far more about this than I do - so thanks for setting me right. The EV6 will be my first EV so my knowledge of all this stuff is very rudimentary! Thanks for the info!

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Bill Schaeffer

· #5 · Jul 14, 2021

Just another question to highlight my current ignorance of all-things EV - do all EVs have inductive battery heaters? Does the EV6?

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jongodfrey

Discussion Starter · #6 · Jul 14, 2021

Bill Schaeffer said:
Just another question to highlight my current ignorance of all-things EV - do all EVs have inductive battery heaters? Does the EV6?

We are pretty sure the EV6 does - see here Interview with Researchers The Story of EV Technology on E-GMP - Hyundai Motor Group TECH
Many do not. For example; the Nissan leaf uses only air cooling, so I think it will be a mix. Tesla do... but only recent models have a heat pump. It's a model by model thing.

By the way, Bill... it's really complicated and very new so we are not alone trying to get an understanding!!

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jongodfrey

Discussion Starter · #7 · Jul 14, 2021

This might make it easier to read and find.

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swaq

· #8 · Jul 15, 2021

jongodfrey said:
I completely get the desire or even need for a HP in cold climates but in temperate climates like South West UK it's less easy to justify the cost.

Is a heat pump really more expensive than adding resistive heating? Cars already have an air conditioner, all you have to do to implement heat pump heating is run that in reverse (requires a switching valve or something).

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jongodfrey

Discussion Starter · #9 · Jul 15, 2021 (Edited)

swaq said:
Is a heat pump really more expensive than adding resistive heating? Cars already have an air conditioner, all you have to do to implement heat pump heating is run that in reverse (requires a switching valve or something).

Really good point, but unfortunately it is. The parts are not cheap. The compression needed for a heat pump is far greater although Tesla have what I think is a combined unit. They call it a three way pump so I am assuming the third way is HAVC. I understand they are harvesting waste heat for the cabin, harvesting heat from the atmosphere and expelling heat to the atmosphere when surplus.

I read that a good Heat Pump will reduce losses by 19% but be careful here as this is NOT 19% increase in winter range as some have suggested. It means if through heating the batteries and heating the cabin you lose 100 miles of range a heat pump will reduce that by (up to) 19 miles, so you still lose 81 miles of range. So optiminstacly this would save 6Kw/h which at a Rapid charge rate of 0.32 would be in the UK £1.92. If you are charing at home that would be £1.14 roughly at current standard tariffs.

Take the rapid number, you'd need to do that for 469 VERY cold days. Heat Pumps efficiency drops off below -5 C (23 deg Fahrenheit) so you still need some inductive heating I believe. In the South West of the UK we get about 15 say 20 such days a year, many years less than 10. You can do your own local math(s) of course.

I should just add, I'm not against the Heat Pump. I tried to add it after I ordered but couldn't unless I lost my place in the queue. I wanted to add it for residual value and also because I like the idea of having it!! 😬 More emotion than logic ...

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Mackemsteve

· #10 · Aug 13, 2021

It's ludicrous that given the price of a GT Line S model that a heat pump is an extra-cost option.

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SheffEV

· #11 · Aug 13, 2021

The wife and I attended the show and tell event at the local dealership and we are mostly convinced by the EV6. I did ask the KIA rep Heat pump to be or not to be, his response a big fat no. As Jon points out the return on the investment of £900 doesn’t really pay off in the efficiency gains, especially for us in the UK.

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jongodfrey

Discussion Starter · #12 · Aug 17, 2021

I agree it really should be included and I would prefer to have one but I can see why for example it would be included in a car for Norway but in the UK it's not easy to justify.

stEVe

· #13 · Sep 16, 2021

jongodfrey said:
I agree it really should be included and I would prefer to have one but I can see why for example it would be included in a car for Norway but in the UK it's not easy to justify.

I'm grateful for this thread because it's made me realise I don't know how to configure the heat pump in. A heat pump scavenges heat from the environment into the car using just a small amount of electricty for the pumping so it's going to be much more efficient than a resistive heater, probaby 2x . I'm going to add it in, the cost is reasonable for the equivalent of aircon, it will probably add 5% to range and prevent range loss on cold days. Although it is hard to justify probably a £20 per year saving for the average 8000 miles a year driver, you get extra range in poor conditions when you most need it and it will probably boost the resale value.

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jongodfrey

Discussion Starter · #14 · Sep 17, 2021

stEVe said:
I'm grateful for this thread because it's made me realise I don't know how to configure the heat pump in. A heat pump scavenges heat from the environment into the car using just a small amount of electricty for the pumping so it's going to be much more efficient than a resistive heater, probaby 2x . I'm going to add it in, the cost is reasonable for the equivalent of aircon, it will probably add 5% to range and prevent range loss on cold days. Although it is hard to justify probably a £20 per year saving for the average 8000 miles a year driver, you get extra range in poor conditions when you most need it and it will probably boost the resale value.

I agree. I opted out for the heat pump and then changed my mind the main reason being residual value.

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Desmo

· #15 · Sep 17, 2021

I added the heat pump to my order. Anything to grab a bit more range and comfort if I can, wasn't worried about any return on investment. The whole car is a depreciating value asset, another £900 is neither here nor there really considering the cost of the car.

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phusebox

· #16 · Oct 11, 2021

Is the heat pump really a must have? I live in mild climate, at worst -10 C during nights (but that is already extreme and only for a handful of days a year).
The thing is, the heat pump would raise the price on the 58 kWh standard version above the limit to be eligible for a government grand. That means the heatpump would cost me 4200 euros effectively as it would cause me to lose the grand.

stEVe

· #17 · Oct 12, 2021

A resistive heater takes energy out the battery and heats the car, a heat pump uses a smaller amount of energy to transfer heat from the environment (yes even on a cold day) so it's more efficient and you get better range when using the heater. If you can find even rough figures e.g. 50% for how much more efficient it is you can multiply the saving from the energy gained by the life of the car and see if it comes to more than EU4200, my guess is it won't.

phusebox

· #18 · Oct 12, 2021

stEVe said:
A resistive heater takes energy out the battery and heats the car, a heat pump uses a smaller amount of energy to transfer heat from the environment (yes even on a cold day) so it's more efficient and you get better range when using the heater. If you can find even rough figures e.g. 50% for how much more efficient it is you can multiply the saving from the energy gained by the life of the car and see if it comes to more than EU4200, my guess is it won't.

So I am guessing the range they are communicating is based on a version with heat pump?
Wondering how much range I would lose. Like 10% or more?

stEVe

· #19 · Oct 12, 2021

So many variables especially the climate where you live. This may give you some idea. https://electrek.co/2020/12/03/tesla-model-3-heat-pump-comparison-results/

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stEVe

· #20 · Oct 14, 2021

phusebox said:
So I am guessing the range they are communicating is based on a version with heat pump?
Wondering how much range I would lose. Like 10% or more?

Here's a really good article on the ins and outs

chargedevs.com

A closer look at why heat pumps are dominating EV HVAC systems - Charged EVs

Heating or cooling the interior cabin of an EV substantially affects the vehicle’s on-road efficiency, and the HVAC system often gets the proverbial “rented mule” treatment. In an ICE vehicle—particularly an underpowered one—there is a visceral reminder that running the AC, at least, costs...

chargedevs.com

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