[jongodfrey]

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

 

[Bill Schaeffer]

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.

 

[jongodfrey]

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.

 

[Bill Schaeffer]

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!

 

[Bill Schaeffer]

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

 

[jongodfrey]

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!!

 

[jongodfrey]

This might make it easier to read and find.

 

[swaq]

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).

 

[jongodfrey]

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 ...