[HN Gopher] Charging electric vehicles 5x faster in subfreezing ...
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Charging electric vehicles 5x faster in subfreezing temps
Author : gnabgib
Score : 37 points
Date : 2025-04-05 00:38 UTC (1 days ago)
(HTM) web link (news.umich.edu)
(TXT) w3m dump (news.umich.edu)
| ajross wrote:
| While the technology may be advantageous, it seems weird to write
| a whole article about it without mentioning the obvious solution:
| Just Heat The Battery. It's true that many early EVs (and most
| non-Teslas even today) don't ship with battery thermal
| management. But they won't be getting new battery chemistry
| either.
|
| This is one of those Great New Technology items that smells like
| a failure simply because it's not competing with the thing the
| designers think it is. It's not enough for this to beat a cold
| battery with a performance delta ("5x", per the article) that
| would justify its additional cost. It has to beat a battery with
| a garden variety heat pump attached, which is a much (much) lower
| cost barrier.
| givinguflac wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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 wrote:
| 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.
| homebrewer wrote:
| I live in a region where -40degC is not unheard of (it
| happens every winter and stays for up to several weeks).
| I've also been to another region (not far off) where
| -50degC is pretty typical.
|
| Gasoline powered engines work just fine in these
| temperatures, although many cars come with auto ignition
| systems that start up the engine periodically throughout
| the night to keep it warm. Otherwise you might have to
| warm it yourself in the morning using a gasoline powered
| "torch" (or whatever it's called), which sometimes ends
| up with the car going up in flames.
|
| So it's honestly pretty funny to read that EV work "down
| to -10degC". Although probably relatively few of us are
| desperate enough to be living in such conditions.
| Rygian wrote:
| https://ashp.neep.org/ for a list of heat pumps that perform
| well in cold weather.
| cyberax wrote:
| You don't even need a heat pump. You can just slightly overvolt
| the charger, so that some electrical energy is lost as heat
| rather get than transformed into chemical bonds.
|
| > This is one of those Great New Technology items that smells
| like a failure simply because it's not competing with the thing
| the designers think it is.
|
| This technology makes no sense for fast DC charging because
| there's enough waste heat to keep up the battery temperature,
| and you can just use some of the power to heat up the battery.
|
| But it can help for slow overnight charging. Keeping battery
| heated all night is wasteful, but you still want to be able to
| charge.
| jjtheblunt wrote:
| > It's true that many early EVs (and most non-Teslas even
| today) don't ship with battery thermal management.
|
| That's false since at latest 2013 in the US.
|
| The past 12 years of BMW as a counterexample all have thermal
| management. Tesla too.
|
| You may be remembering the original Nissan Leaf?
| ajross wrote:
| Almost all non-Tesla EVs offer a heat pump option. Most non-
| Tesla EVs sold do not have one. Just go to your local VW
| dealer or whatever and see what the specs are on the ID.4's
| on the lot is.
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