Cold weather warning

The use of accessory-only is a warning for all generations of all Toyota hybrids... Don't!

The reason why is simple, it drains the 12-Volt battery within any way to prevent draining it entirely.

Turning the vehicle on to READY is the recommended choice.

 

I don't understand why Toyota even kept ACC mode on Prime (or any of Prius). Is there any good reason that ACC mode is needed over just keeping the car on READY mode?

 

So, of course, one needs to be aware of the limits of ACC mode, but there definitely are situations where you'd want to use ACC instead of READY. For example, whenever the ICE would switch on, such as in cold weather or with climate control on, you'd rather use ACC for simple tasks because when the ICE starts, you'd want to let it finish the warm-up cycle rather than shut it down while still running. I'm speaking of the Prius Hybrid, maybe the Prime doesn't start the ICE in all the situations where the Hybrid does.

 

Yeah, for Prime if there is enough charge in the traction battery unless the temp is below 14F and the heater is on or the front defroster switch is turned on, the engine will not come on. But I guess I can see a situation ACC is useful, like when I may just want to push the START button without sitting on the seat to depress the brake pedal so that say I can close the windows I forgot to close. But still... I can do without ACC and more so without IG-ON mode.

 

Probably mandatory to have it? With a traditional car with starter, the 12 volts were a lot more robust, for sure.

 

Nothin wrong with experimentin with the car, as long as you've first checked out what possible issues may show up while experimenting.
I did a smilar experiment to the OP in the first year, but in ready mode while sittin g in the car and monitoring the use of the Traction Pack at the HVAC setting and ambient temps. It took less than 5 minutes to collect the data.

 

Regarding the OP's situation, if the car is plugged in, then the car does not go into READY mode. My understanding is that in non-READY mode, either in ACC mode or in IG-ON mode, the hybrid system and the traction battery is totally disengaged. Is that mean there is no way to heat (or cool) the cabin using HVAC since the traction battery can not supply the power for the heat pump? All the fans and resistive seat heater would be running off of the 12v alone and no charge going into the 12v battery. If this is correct, then how does the remote A/C from the fob or the Climate Prep by charge schedule work off of the traction battery while the car is OFF and plugged in?