Heat pump, and remote AC, but no preheating???

Glad you agree with me...

 

The definition of "preconditioning" is already all over the place. First, it was referred to as a battery warming method from using cabin air. Then it was direct for providing full operational temperature. Next, it was to just keep above freezing to allow recharging.

That raises a bunch of red-flags. Misconceptions emerge from the lack of clarity. Greenwashing emerges from no one making an effort to stop the exploitation of assumptions caused by so many vague mentions.

The first that jumps out is that the battery cannot be charged when its temperature is below freezing. That is implied and certainly could be interpreted that way. It's false, of course. The warming is to make the process more efficient. Colder means higher resistance, which means more electricity will be consumed as part of the transfer process (in both directions, charging & drawing).

The next problem would likely be the belief that EV simply isn't available if the temperature of the battery drops below freezing. That most definitely isn't true either. It's not as efficient, but drawing electricity for driving certainly is available. If you push demand, by firing up the heater or pushing speed & power, the lack of warming would require the gas engine to join in at some point. But we know for certain even the Prius PHV from 2012 can deliver EV at 50 mph without any trouble at 20°F just fine. I would do that routinely with mine, and it didn't have any warming feature.

Then there's the confusion of cabin warming. The system will use the heat-pump for that. Even the better informed will pause to consider whether the battery is used for that or if electricity is drawn directly from the plug. Then they'll question what happens with timing and the charge-rate at different capacities and with faster chargers.

Needless to say, topics like this open up a new cans of worms for us to deal with.

 

but a fun can.

 

That's not entirely accurate. Since the electrolyte is basically a solid below 34C (93F) anyways, the temperature of the electrolyte is not really at issue here. I've recharged my PiP after it sat outside in not quite sub zero (F) temperature and have data that shows the battery temp in the 20s. @bisco is correct, its not as efficient but nowhere's near inoperable.


Unsupervised!

 

We are here for fun! Isn't it?

 

you betcha!

 

So we will now be able to preheat the cabin out of doors without the long arm of the law getting an attitude about leaving the car idling unattended and indoors without the carbon-monoxide exhaust risk.

Somewhat concerned about reliability and repair expense with the more complex system from years of restaurant refrigeration and hvac experience.

Wonder how many watt-hours the battery resistance heater will consume? Need to take that into account when calculating distance per kilowatt. Will we be able to read this value as a separate can code? Can it be disabled to save electrical costs?

These Lithium-ion cells are to efficient at level 1 or 2 charging rates to heat themselves hence the need for built-in battery heaters under cooler temperatures. Tesla has always had and needed this. They just don't like to count the kilowatts it uses. Acceleration and regen current flows into and out of the cells are the big producers of heat. If you reduce the current drain from cold cells so that the voltage follows its discharge curve given at the higher spec. temperature you get the full rated power out of them but you will be going really slow. Deliberate regen induced heating of the cells is a technique I haven't seen explored yet for cold weather performance. Pulse and regen for pack heat and range?

 

i have to assume that heating the batteries takes less electrons than would be lost by charging or driving cold.

 

Or it allows charging to proceed at a reasonable pace.

 

I am a bit disappointed that it seems now that heating the battery is only used to get it just above the freezing point. That is still rather cold. I would prefer that the heating could get the battery temperature at a level, for example, of 20 degrees C or 70 F. These are the temperatures in summer for which you have the higher EV ranges. Charging around the freezing point will still come with a reduced EV range.

 

Not sure if Toyota has it on a spec sheet yet, but it does. It has been mentioned in a few reviews. Here is one:

2017 Toyota Prius Prime Second Drive Roadtest Review | Automobile Magazine

Through the app you can program your car to charge during off-peak hours to save money on fuel, or even set the climate control or battery warmer to get going before you head off to work so as to not waste energy on your commute.​

 

I live in Minnesota and have driven through 4 harsh withers with my Prius PHV. My experience reveals there's a big payoff below freezing and very little in comparison above. That's not cold by our measure either.

 

In my case I get around 23 km EV range in summer and around 17 km in winter when temperatures are just above the freezing point, that is a reduction by 25 to 30%. I would prefer a lower reduction percentage.

 

On the battery heater subject:
This is a great improvement for those who suffer from very cold winters.
The fact that the heater is on as long as the plug is connected to the car (during and after charging) indicates that it draws its power from the grid (as should be).
I can imagine that the possibility of raising (and keeping) battery temp to around 20C did not elude from the designers, there were probably other aspects that were against this. One that comes to my mind may be battery health an life expectancy: what if the plug is disconnected after charging (or electricity shut off) but the car is not driven for hours (or even days) in sub freezing environment? The fully charged (at 20C) battery could become considerably overcharged for the ambient temp which is not healthy if done as a habit.

 

I get a roughly 20% reduction in my conventional gas car. This can mostly be traced to an increase in tire rolling resistance at cold temperatures.

 

if tesla hasn't figured out how to overcome this, why would we expect toyota to?

 

Probably one of the reasons why Toyota prefers smaller batteries. They know you are going to discharge them at least a little bit if you go somewhere. But you are correct, a Lithium based battery is best left not fully charged at any temperature. As long as everybody follows Toyota's Owner's Manual you should be set. For instance on Page 117 it says: "Do not charge if the outside temperature is -30 °C (-22 °F) or below, as it is likely that charging will take longer, and equipment related to charging will be damaged.".


Unsupervised!

 

agreed. i'm sure prime will come with even more warnings and disclaimers than pip. lawyers will be the last to have a crack at it.

 

What would they be? You've got a system with increased system flexibility now. That would equate to less.

The bigger "issue" is how people interpret the results.

 

I think most people asking for preconditioning are asking for something that warms up the battery while they have the cabin precondition. This system is for keeping the battery out of temperatures where the charge rate real be slow to avoid battery damage, and staying out of sub-zero temperatures could extend the battery life.

There is no technical reason that both would not be possible. There is already a top buffer to the battery's SOC so there wouldn't be an actual overcharge, and the system could use battery power for heating to bleed excess energy off if need be.

People that use block heaters report that the loss is reduced. Gen2 Prius owners would use them year round to reduce the fuel burning warm up cycle.

Because Tesla has overcome this. The liquid thermal control system that they and GM use keeps the battery warmer for more efficient charging, and heat up the battery faster than warm air would.