PHEV/Prime Low Temperature concerns

Have you got the cold region setting enabled? It should be keeping the battery from getting too low to operate while plugged in. If you've got a charging schedule set, and the cold region setting is on, it should show a message about the schedule being overridden at those temperatures. Not sure if it flags it up otherwise.

This is a setting that has to be set via a scantool - dealer can do it and probably are supposed to have done.

 

The manual for my HEV says the same thing:

 

It's a drawback of Li-ion. Operating at those temps could damage the battery even if it could provide energy. Then the gen5 PHV has the battery outside the cabin space where it can lose heat faster.

The cold climate setting will run the battery heater for longer while parked than the default. But it isn't high power; temps that low might be too much for it.

 

Right, and that's the point of the PHEV Greenland/Canada cold weather setting - to give you a way to stop the battery going below -30°C by plugging the car in. Especially needed with the battery exposed on the outside.

The normal "battery heater" selectable via the options screen operates from something like -10°C to 0°C, trying to keep the battery above freezing so it operates efficiently, with the aim being to avoid needing to start the engine. At temperatures below somewhere between -10°C and -15°C it gives up, presumably knowing the engine's just going to have to start. That operates for up to 3 days.

The cold weather setting starts heating operation somewhere below -20°C to make sure the battery doesn't get cold enough to not work, and that operates for up to a month.

I managed to profile the battery heater's behaviour in this thread. It hasn't got cold enough here to analyse the Greenland/Canada setting in detail.

But it's clear here in Finland why it's a setting - the chances of the weather hitting and staying around -25°C here for a period are relatively high, but the chances of getting as low as -30°C are minimal. So having it on and consuming electricity at -25°C to tend the battery would be pointless - there's been no sign of the car being reluctant to start.

I assume the limited power is part of why it's an option - to stop the battery getting below -30°C it wants to start while there's still plenty of margin. It's not being tasked with literally heating the battery - it's being tasked with sustaining its temperature.

It just has to keep up with whatever heat loss there is with a 10-to-15 degree difference. If it can get the battery to 0°C when it's -10°C outside, it should be able to hold it at -28°C when it's -38°C outside.