[RobinB]

On my Maxx if plugged in with the charge completed ( for example I tend to charge between 00.30 and 04.30), if remote heating is activated it starts to charge pulling around 7kwh from my wall charger.

Yep - Cocijo is right. The pre-heat is designed to work from external power. The AC power has to be available from the cable. It was a design to maximise people's battery range by heating the car from the mains before you get in, you begin your journey on 100% SOC and the car is already warm, so it is only having to use relatively little energy keeping the temperature topped-up.

I don't have a Soul EV yet but would guess that if the charger is off then it would use the main battery.
Can you check the charger status, separate from the car, to see if it's operating during the preheat process?

Nope, sorry. Scheduled pre-heating requires to be plugged in. It says so in the manual. Plugged-in with no volts doesn't work as a cheat!

If you want the car warmed at the expense of the battery you can do it, but it has to be by using the Connect app to manually start remote climate. I guess they don't mind this because the use-case is for a human making a decision that climate is required "now" (whether that is cooling the car in a hot summer car park or warming it or warming it outside your home).

Imagine if you had an "all week" schedule and forget to plug in one night you might lose a bit of SOC, but go away for a week or more and you have the makings of a problem!

Unfortunately the "scheduled climate" is more of a problem with people who have smart chargers which of necessity follow agile tariffs. For simple off-peak times you might as well use the settings in the car and ignore timers in the smart wall-box.
If you only want to use the kWh from the cheap time then you have to use the Connect app to manually start during your breakfast - You can't schedule heating from battery.

 

[RobinB]

That’s useful info. I didn’t realise that for scheduled heating to work it needed to be plugged in.
I tend to use the app and activate mine and not use scheduled heating.
So, I guess the remote heating activation just engages the 12v battery unless the car is plugged in, in which case the HV engages and charges the 12v, and for scheduled climate it needs to be plugged in.
I’ve noticed that when i activate remote climate, if the car is plugged in it starts to draw from the charger, which makes sense. I suppose if the 12v was low remote climate either wouldn’t work or would drain the 12v if not plugged in?

Actually the remote heating via the Connect app does enable the high-voltage battery. I think if it just took that sort of heating current out of the 12V battery it would be flat pretty quick. If you weren't plugged-in the car would heat (or cool) and would have turned on the high-voltage systems so as to provide plenty of 12V power (via the LDC).
What you are seeing at the wall box is the way that the car is taking in 240V from the available mains to feed to the charger to keep topping up the high voltage system. You are drawing from a battery whilst it still has a charger.
I suppose that would mean that we might find that if you were on a 7kW supply the (main) battery SOC would stay at 100%, but if you were only on a granny charger the SOC would drop because the heating would be > the charge going in, but not drop as much as if the car was not on charge.
I think I recall saying in some conversation about heat pumps that I'd seen several kW being used in the first minutes of getting into a freezing car, but after driving for a while and the car warming the watts consumed by "climate" in the "EV" display were only around 500W, so either the fact the car had warmed or the heat pump was salvaging spare heat from the motor, electronics and surroundings. If a car was pre-heating with several kW (let's guess at 2kW in the absence af a fact coming to hand) at 12V that would require 167 Amps, sustained for 10-20 minutes!

...I tend to use the app and activate mine and not use scheduled heating.

Yep - That's the only way I can heat mine because I don't have home charging. I was used to using the phone app to cool the car in hot places last summer and I find the idea of doing it from an app just fine, exactly when I want it and not at other times, often when walking to the car.
I have used it a few times to heat when I'm collecting from a charging lamppost. I feel a bit wasteful, but it's "a test" in my mind ;-) The novelty of climate when still connected to external power.