HV Battery temperature control

Some interesting photos of cutaway models of the Prius Prime battery on the hybridlife website under the title "Toyota Prius 4 rechargeable: les derniers details devoiles au".

It appears from these photos that cell cooling/heating is achieved by drawing air from the cabin, up between the cells and out through two centrifugal fans exhausting to the outside through the rear floor pan. Moreover it seems that the battery case has built-in channels (making it almost double-walled) through which some of this air can also be directed. This is presumably to help heat-up or cool-down and perhaps also to avoid condensation inside the battery case when warm humid cabin air is drawn through a cold case.

Below each of 5 banks of cells there are two resistive strip heaters, one of which Toyota has labelled "battery heater" and the other "battery warming system".

From the owners manual, battery cooling is apparently achieved by cooling the air using the cabin air conditioning system. The owners manual also indicates that a "battery heater" will keep the battery at around 32F while plugged in (presumably to avoid charging at lower temperatures, which is not good for lithium ion cells). After 3 days in this mode however, the manual says the car will exit this mode and stop heating the cells (presumably to save energy, since I believe the battery heater draws around 1.4kW).

If, however you have a Canadian or Alaskan car, another system will kick-in (as per owners manual) following the 3-day trip. That system applies for 31 days and will until then start the charging process as soon as the car is plugged in (over-riding any call for delayed charging). It will also apply "battery warming" (as opposed to "battery heating").

So it seems that for Canadian & Alaskan cars there is a special heating mode for cars that are not used regularly (i.e., left more than 3 days on the charger without unplugging). Prior to the mode switchover the design philosophy is to keep the battery above 32F until the pre-programmed charge time. But after switchover the car will start charging as soon as it is plugged in (when presumably it is still warm from use), and then keep it "warm" (which may mean at a lower temperature than 32F) until it is driven. This would be entirely reasonable since using a lithium ion battery at temperatures much lower than 32F is not a problem, but charging one at low temperatures can result in permanent damage.

There is one other thing that the owners manual says happens when the car does this mode switch-over... the battery somehow "insulates" itself. Here is how it is worded:
Hybrid battery (traction battery) warming control (Alaska and
Canada only) This control operates after the charging cable remains connected to
the vehicle for 3 days and “Traction Battery Heater” automatically
stops. It automatically insulates the hybrid battery (traction battery)
in extremely low temperatures.

Could they mean "isolates" instead of "insulates"?...Perhaps the inlet and outlet air ducts close to try to conserve heat?

I would appreciate any comment or thought that others have on any of this, as I live in a pretty cold part of Canada and want to understand the inner workings of the Prime's system so I can best adapt my charging routines to it.

On a related note:
For those of us living where winter temperatures are often below the 14F threshold for effective heat pump warming of the cabin, it would sure be nice if the Prime would allow us to remotely start the engine without having to go outside to unplug the vehicle. The Volt allows this, but for some reason the Prime disables both the gearshift and the ICE start-up when the charge cable is plugged in.

 

Thanks Elektroingenieur for the further insights.
The battery is pretty easy to get at, so when I get my Prime (dealer here in Ontario, Canada tells me early March) I will figure out how the battery heating system works on a Canadian car and report back.
I haven't been able to access any info through Toyota's techinfo site (paid $15 for a 2 day subscription but couldn't find a way to open it with my Mac), other than to look at the list of manuals/literature available there for the Prime.
It would seem that full service documentation (like the 5 or 6 manuals I have for my 2005 Prius) is not yet available. Is that true?
In your opinion does the TIS system currently have enough worthwhile tech info on the Prime to warrant me buying a cheap ebay PC as well as paying for a month TIS subscription?