R1T / R1S EPA Test Documentation Confirms Some Details: 210 kW peak DC charging, no heat pump

[BigSkies]

Reading between the lines, my understanding is that heat pumps are relatively new technology when applied to cars (albeit not generally). Essentially, there aren’t any third party manufacturers that can provide them, and they’re a decently heavy R&D lift to design in-house.

I think it’s a reasonable assumption that it just wasn’t an R&D priority for getting the first model year out. I’d be willing to bet they’ll develop one within a few years. Look forward a decade, and they’ll probably be standard on all EV’s.

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[SeaGeo]

Brice, does insomnia run in your family? Lol!!

Ha. No. And thankfully I don't have it either. Just a screwed up sleep schedule at the moment that I'm doing a poor job fixing.

 

[ajdelange]

Guess it's time to explain again what a heat pump is. It is a device that pumps heat, that is transfers it from a "reservoir" at low temperature to one at high temperature. Heat flows naturally from high temperature to low and is actually capable of doing work as it does so (this is how "heat engines" such as an ICE engine basically work). Conversely if you want to pump heat "uphill" (cool reservoir to a hot one) you must supply work. Your Rivian has a heat pump. It pumps heat from the cabin (75 °F) to the ambient (95 °F) when you have the A/C on. The Tesla vehicles obviously do the same but some of them are also able to pump heat in the opposite direction too that is from, say, 35 °F ambient air into a 70 °F cabin. In common parlance the two way arrangement is called a "heat pump" whereas the one way device is called an "air conditioner". The difference between to two is that the "heat pump" has a "reversing valve" whereby the direction of refrigerant flow can be reversed. In A/C mode hot gas from the compressor flows to a condenser in the ambient air stream where heat is removed from it causing it to condense into a liquid. This then flows to an "evaporator" inside the car where it boils removing heat from the cabin. The vapor is returned to the compressor. In heating mode the hot gas from the compressor goes to the cabin heat exchanger first where it dumps heat and condenses to a liquid. This is then piped to to the exterior heat exchanger where the outside air, even though it be at freezing or below, is hot enough to boil the refrigerant thus absorbing heat from the air. The vapor returns to the compressor. Thus a "heat pump" is able to swap condenser and evaporator roles and it does this through clever valve and plumbing arrangements (Tesla Octovalve). The reason for doing all this is that 1 kW of power can pump more than 1 kW of heat. In the 40's (F) a kW invested in running the compressor may yield 4 or more kW of heat. This is obviously, from a range POV, vastly superior to a resistive (be it PTC or otherwise) heater. The bad news is that as the temperature drops below freezing the COP drops too approaching 1 (1 kW electricity gives 1 kW heat).

Is it worth the extra design complexity? Depends on where, how and when you drive.

 

[Drterreur]

Reading between the lines, my understanding is that heat pumps are relatively new technology when applied to cars (albeit not generally). Essentially, there aren’t any third party manufacturers that can provide them, and they’re a decently heavy R&D lift to design in-house.

I think it’s a reasonable assumption that it just wasn’t an R&D priority for getting the first model year out. I’d be willing to bet they’ll develop one within a few years. Look forward a decade, and they’ll probably be standard on all EV’s.

My recollection is that in order to work perfectly in a wide range of climate, a heat pump was not an option as it ceased working efficiently at low temp.

The heat pump vs resistive heating may be a mood point. There may be more benefit to efficiently recuperate wasted heat from other system while driving such as from the battery.

 

[R1S Maineiac]

Re the peak charging - could it be the actual peak at the time of the EPA test vs what they might be able to expand achieve later? As in they had to use the "now" figures vs whatever they think might be possible "soon"?

It's possible that when they have enough real world data(or their own network is available), they push an update to unlock more speed.

210 isn't really anything to complain about, as long as it can hold it until at least 50% soc.

 

[SeaGeo]

It's possible that when they have enough real world data(or their own network is available), they push an update to unlock more speed.

210 isn't really anything to complain about, as long as it can hold it until at least 50% soc.

I interpret this as being there possible for the current hardware. Not what to expect in the current rollout. The uncertainty is exactly my frustration with Rivian.

And I agree if it holds near max well into the pack, that would be great. The current curve does not seem as aggressive as what you or I would hope for. They can definitely refine on the shape of the curve though.

 

[R1S Maineiac]

I interpret this as being there possible for the current hardware. Not what to expect in the current rollout. The uncertainty is exactly my frustration with Rivian.

And I agree if it holds near max well into the pack, that would be great. The current curve does not seem as aggressive as what you or I would hope for. They can definitely refine on the shape of the curve though.

So, we all know the responsibility of the first customer deliveries:

Charging videos!!

 

[SeaGeo]

So, we all know the responsibility of the first customer deliveries:

Charging videos!!

Yup.

BTW, I know owners are pulling 185 up to about 35%. Seems to drop off after that. I haven't heard of any owner pulling 210 yet. I do suspect they're just being conservative with the curve to get one data.

 

[the long way downunder]

Heat Pumps sound good on paper, but if it gets cold or hot, they stop working well.

In my experience as it gets warmer around here they tend to work less, and in the winter they feel like they're blowing cold air vs something hot like with a regular design.

May be different in cars, but after owning several for 18 years on our home, i'm not convinced they're great in our climate.

I think Tesla says the opposite – heat pumps excel in extremes (in automotive applications, not necessary household systems.) Also, heat exchangers have come a long way (Tesla invented their own "octovalve" to simplify the system (literally hundreds of fewer pipes and connectors) and increase efficiency over their earlier conventional compressor circuit.
The only downside to a heat pump is its size and noise levels – compared to the sum of all systems in the compressor system with battery thermal management, it's a win, but the noise was an issue (Tesla soon designed an enclosure to suppress the pump noise and retrofitted it to early production vehicles.)

 

[the long way downunder]

I think this is the section for climate control. Not sure what a PTC heater is. Can anyone explain?

Also, this may be new to me, but I've never heard of "Auto humidity control" inside a vehicle. That would be awesome in the South!

Positive Temperature Coefficient (PTC) heaters are the conventional old pair to the compressor A/C for cold air. Of course ICEs generate so much heat a PTC heater doesn't do a lot of work, but in an EV, the PTC heater is a major load.
There's no defying the laws of physics, captain, so if the battery is cold, it has to use its own energy to heat itself in order to be efficient in providing energy to the traction motors. But a heat pump makes that a more efficient total system (at least in the example of Tesla.)
That Rivian has gone ahead without a heat means that somewhere down the line, say the '23 or '24 model year, to gain efficiency and range, Rivian will convert to a heat pump.
I'm guessing this shortcoming was a hard decision to get the product to market and remove R&D items from the critical path.

 

[SeaGeo]

I think Tesla says the opposite – heat pumps excel in extremes (in automotive applications, not necessary household systems.) Also, heat exchangers have come a long way (Tesla invented their own "octovalve" to simplify the system (literally hundreds of fewer pipes and connectors) and increase efficiency over their earlier conventional compressor circuit.
The only downside to a heat pump is its size and noise levels – compared to the sum of all systems in the compressor system with battery thermal management, it's a win, but the noise was an issue (Tesla soon designed an enclosure to suppress the pump noise and retrofitted it to early production vehicles.)

No. That's why they've been criticized and had some issues with heat pump performance cold climates.

Edited to add a source:
https://www.moncriefair.com/blog/at-what-temperature-does-a-heat-pump-stop-being-effective/

 

[the long way downunder]

No. That's why they've been criticized and had some issues with heat pump performance cold climates.

Edited to add a source:
https://www.moncriefair.com/blog/at-what-temperature-does-a-heat-pump-stop-being-effective/

I think there are definitely people who've had real problems with the heat pump, especially early on in the Y. I don't know that Tesla has solved the limits of extreme cold (far below zero) but anywhere between blizzards and deserts, it's fine, just not the colder parts of Canada or maybe Death Valley.
Maybe Rivian decided in a big ship, the gains don't outweigh the compromises when the truck is sitting on a rock in Moab and the cabin temp is 80 on a 110 degree day.

 

[dleepnw]

210kw is fine with me as long as it stays high most of the charging session. My Tesla model 3, even if it has the capacity to charge for 2-3 min at 245kw, settles down a 145kw ish until 60%...

It'll be good to know what the charging curve is but my guess is they haven't nailed it down yet. I'm sure they've had some ideas going into deliveries to customers but now that they are out there with employees they are probably tweaking it some more. They probably had ideal charge curves based on the idea that the RAN network would be in place but in the real world we have charge point, EA and home charging so might need adjustment.

 

[Monkey]

210kw is fine with me as long as it stays high most of the charging session. My Tesla model 3, even if it has the capacity to charge for 2-3 min at 245kw, settles down a 145kw ish until 60%...

This right here.... I don't car if it tops out at 180kW, it's all about the charging curve and what it can maintain for a certain length of time or average over the entire charge. Our Model Y starts off great and then slows quickly. I don't stop at Superchargers often, really just when on road trips. I never charge beyond 65% or so unless I have to because then I'm just waiting forever for very little gain. I make sure I have enough to make the next stop plus maybe 20% more just in case.

 

[SeaGeo]

It'll be good to know what the charging curve is but my guess is they haven't nailed it down yet. I'm sure they've had some ideas going into deliveries to customers but now that they are out there with employees they are probably tweaking it some more. They probably had ideal charge curves based on the idea that the RAN network would be in place but in the real world we have charge point, EA and home charging so might need adjustment.

Shouldn't matter. Electrons are electrons. As DuckTruck mentioned from June, it sounds like they may reward "good behavior" through the bms and open up more aggressive curves to manage longevity, and then keep it disabled back for those who are harder on the battery. But they're also probably just playing it safe for now too. If you remember, Emme said they pulled 180+ for basically all the way to 80% st the RR, but that's not what the current curves are doing. So it at least sounds like the hardware is there to manage the temps.

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