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Heat pumps struggle to do much at the temperature range the article proposes. Edit: downvote me all you want, I was responding specifically to “It has to beat

Heat pumps struggle to do much at the temperature range the article proposes. Edit: downvote me all you want, I was responding specifically to “It has to beat a battery with a garden variety heat pump attached” of which EV heat pumps are not garden variety heat pumps, which do struggle at those temperatures. Didn’t think I had to be so pedantic.

Kirby64 2y ago
Pretty sure the ones in most EVs today work fine at -10C, but they may lose some efficiency. The thing is, there's already mechanisms in some cars to generate waste heat specifically for this purpose. Tesla's already have the ability to run their motors 'inefficiently' generating waste heat, which can be pumped into the battery coolant and heat that. It's no better than electric strip heating, but it doesn't add any cost to the system. The real benefit, in my view, to being able to charge at cold temps is to improve overall efficiency. If you have to waste some amount of power to heat the battery then that is power that could have been used to charge the car instead...
- superkuh 2y ago
  You bring up a great point. The battery spec is only given at -10C. That's a mild normal day's low temperature in winter in Minneapolis, USA. But it's often much colder than that for long periods of time. I wonder if this glassy layer they apply can handle -30C; a temp where above ground heat pumps are no better than electrical resistive heating.
ajross 2y ago
The 5x delta is stated to be at 14F. That absolutely is within the reasonable operating range of a Model Y heat pump, not sure what you're citing? It's true that there are very cold environments (Fairbanks winters, say) where in-car thermal management won't be sufficient to keep charging rates high. But those are the same environments where you can't even start a gasoline car without an engine block heater, and I don't see many "no cars in Alaska" arguments on the internet. Everything has limits, but I don't see this battery trickery having much of a home.
- idiotsecant 2y ago
  You can start gasoline cars just fine down to 20 or 30 below, so long as you keep a good battery in it. Sometimes big diesel trucks use block heaters but gasoline cars don't need them.
  - lstodd 2y ago
    I can definitely say that old/USSR 2.7L gasoline engines for the military came with block heaters. But they were expected to start in -50C / -60F. Good luck getting anything out of an EV at those temperatures.
    - gambiting 2y ago
      There's plenty of Norwegians on YouTube testing EVs down to those kinds of temperatures and they work absolutely fine, with the caveat that they won't charge until the battery warms up. Discharging Lithium batteries at really low temperatures isn't an issue, charging them is(because it actively damages them) - but even then the threshold is -32C or around that, easily overcome even with a simple resistive heater.
      - lstodd 2y ago
        Norway is not "those kind of temperatures". They get a lot of snow, and maybe -5C and that is all because Gulfstream (the reason Murmansk does not freeze, and it's much farther into Arctic). Otherwise they get it easy. Now when you move just a bit off the sea, the continental climate kicks in, and you have weeks of -15 -- -20C. On discharging lithium chemistries at those temperatures or "easily overcame with resistive" let me say that: you just don't know what you are talking about.
    - mschuster91 2y ago
      The question is, how many people are legitimately living in areas where this is an actual concern in their lives? Outside of Alaska, Canada and Russia barely any place on Earth that relevant amounts of people live in, such low temperatures are a once-in-a-lifetime event.
Rygian 2y ago
https://ashp.neep.org/ https://ashp.neep.org/ for a list of heat pumps that perform well in cold weather.
deleted 2y ago
[deleted]

Kirby64 2y ago

Pretty sure the ones in most EVs today work fine at -10C, but they may lose some efficiency. The thing is, there's already mechanisms in some cars to generate waste heat specifically for this purpose. Tesla's already have the ability to run their motors 'inefficiently' generating waste heat, which can be pumped into the battery coolant and heat that. It's no better than electric strip heating, but it doesn't add any cost to the system. The real benefit, in my view, to being able to charge at cold temps is to improve overall efficiency. If you have to waste some amount of power to heat the battery then that is power that could have been used to charge the car instead...

superkuh 2y ago
You bring up a great point. The battery spec is only given at -10C. That's a mild normal day's low temperature in winter in Minneapolis, USA. But it's often much colder than that for long periods of time. I wonder if this glassy layer they apply can handle -30C; a temp where above ground heat pumps are no better than electrical resistive heating.

ajross 2y ago

The 5x delta is stated to be at 14F. That absolutely is within the reasonable operating range of a Model Y heat pump, not sure what you're citing? It's true that there are very cold environments (Fairbanks winters, say) where in-car thermal management won't be sufficient to keep charging rates high. But those are the same environments where you can't even start a gasoline car without an engine block heater, and I don't see many "no cars in Alaska" arguments on the internet. Everything has limits, but I don't see this battery trickery having much of a home.

idiotsecant 2y ago
You can start gasoline cars just fine down to 20 or 30 below, so long as you keep a good battery in it. Sometimes big diesel trucks use block heaters but gasoline cars don't need them.
- lstodd 2y ago
  I can definitely say that old/USSR 2.7L gasoline engines for the military came with block heaters. But they were expected to start in -50C / -60F. Good luck getting anything out of an EV at those temperatures.
  - gambiting 2y ago
    There's plenty of Norwegians on YouTube testing EVs down to those kinds of temperatures and they work absolutely fine, with the caveat that they won't charge until the battery warms up. Discharging Lithium batteries at really low temperatures isn't an issue, charging them is(because it actively damages them) - but even then the threshold is -32C or around that, easily overcome even with a simple resistive heater.
    - lstodd 2y ago
      Norway is not "those kind of temperatures". They get a lot of snow, and maybe -5C and that is all because Gulfstream (the reason Murmansk does not freeze, and it's much farther into Arctic). Otherwise they get it easy. Now when you move just a bit off the sea, the continental climate kicks in, and you have weeks of -15 -- -20C. On discharging lithium chemistries at those temperatures or "easily overcame with resistive" let me say that: you just don't know what you are talking about.
  - mschuster91 2y ago
    The question is, how many people are legitimately living in areas where this is an actual concern in their lives? Outside of Alaska, Canada and Russia barely any place on Earth that relevant amounts of people live in, such low temperatures are a once-in-a-lifetime event.

Rygian 2y ago

https://ashp.neep.org/ https://ashp.neep.org/ for a list of heat pumps that perform well in cold weather.

deleted 2y ago

[deleted]