Heated External Mirrors

[LexusIS300h]

Sorry if this sounds like a “derr” question, but I haven’t had a car with heated wing mirrors before and the IS300h has them. How exactly do they start heating as I can’t see anything about that in the operating manual? I don’t see an obvious button to press either.

I thought I would get this question in before they are likely to be needed, now that summer has deserted us 

[NemesisUK]

Press the rear demist button on the climate control panel. The door mirror heaters come and go off, with the rear screen heater.

Took me a while to figure out as the door mirror heaters were automatic on my Mercedes.

[ianhu]

Button looks like this

Sent from my SM-G965F using Tapatalk

[LexusIS300h]

Thank you for the replies, I feel better knowing it’s there now 👍

Pretty obvious now when I zoomed up the image and it’s a wing mirror 😂, just thought it was the rear heater pic again. 

[NemesisUK]

And very effective they are too! Great knowing that one can't discharge the 12v Battery with these functions as they are all powered from the hybrid (traction) Battery. 😁

[Britprius]

1 hour ago, NemesisUK said:

And very effective they are too! Great knowing that one can't discharge the 12v battery with these functions as they are all powered from the hybrid (traction) battery. 😁

The heated mirrors, and screen run directly off the 12 volt Battery as does the heater fan, and engine coolant circulation pump to the heater. Further they will work in accessory mode "2 pushes of the start button with no brake pedal". In this mode the HV Battery is completely disconnected from the car, and cannot charge the 12 volt Battery. Anything that works in accessory mode runs from the 12 volt Battery.

The only things that work directly off the HV Battery are the transmission, the AC, 12 volt charging system, and the power steering. These will only work in ready mode. It would be dangerous for the HV supply to go out to ancillaries such as the mirrors. 

John

[NemesisUK]

3 minutes ago, Britprius said:

The heated mirrors, and screen run directly off the 12 volt battery as does the heater fan, and engine coolant circulation pump to the heater. Further they will work in accessory mode "2 pushes of the start button with no brake pedal". In this mode the HV battery is completely disconnected from the car, and cannot charge the 12 volt battery. Anything that works in accessory mode runs from the 12 volt battery.

The only things that work directly off the HV battery are the transmission, the AC, 12 volt charging system, and the power steering. These will only work in ready mode. It would be dangerous for the HV supply to go out to ancillaries such as the mirrors. 

John

Correct but unless you're in accessory mode (not recommended for any length of time) the 12v Battery is constantly recharged via the traction Battery, unlike in non-hybrid cars, where one relies on the alternator to recharge the Battery, which it only does after supplying any running demand.

So running accessories on non-hybrid car can result in depleting the Battery charge quite quickly. Something hybrid cars wont suffer from.

[Britprius]

26 minutes ago, NemesisUK said:

Correct but unless you're in accessory mode (not recommended for any length of time) the 12v battery is constantly recharged via the traction battery, unlike in non-hybrid cars, where one relies on the alternator to recharge the battery, which it only does after supplying any running demand.

So running accessories on non-hybrid car can result in depleting the battery charge quite quickly. Something hybrid cars wont suffer from.

Even in ready mode if the car is in neutral the system is not capable of looking after it's self since in neutral the engine cannot start, and therefore cannot charge the HV Battery. This once depleted stops charging the 12 volt Battery. It must be remembered that the HV Battery has very limited working amp hour capacity of approximately 2.6 AH, and may be running the AC from this supply. 

The DC to DC converter charges the Battery, and is controlled in much the same way as an alternator by monitoring the voltage at the Battery, and adjusting it's output to compensate for any load applied. A fall in voltage will increase the output of both systems. The difference is that the alternator must be turning "engine running" to work. In a hybrid the HV Battery must have enough charge to run the converter, and be in ready mode in any gear position other than neutral "the hybrid equivalent" of the engine running.

In both scenarios all electrics are powered from the engine via an alternator.

John.

[NemesisUK]

I've found the hybrid Battery can sustain the audio and climate (a/c running) for quite a considerable time, in excess of 1/2hr. before the engine cuts in. 

In winter it's only 10min or less, depending on ambient temperatures but this is simply heat demand from the engine cooling system 

All things considered I find the hybrid system is far more tolerant to electrical demands than any non-hybrid I've owned.  Damned fine cars