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PHEV Remote Aircon... which battery is used when?


Nick72
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Probably a simple answer here but if I remote start the aircon from the App or the key fob button which Battery is used?

The tiny 12V Battery which would make no sense?

Or, the massive traction Battery which would make all the sense in the world.

 

And, what if i use the App to enable the rear window defrosting. Which Battery is that using?

27C today but already planning for winter! Don't want a flat Battery when I'm at work and I start the defrosting. At home the car will be plugged in during winter each day so I assume that any aircon and defrosting electrons come from my wall box?

Thanks again all.

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3 minutes ago, ernieb said:

Traction.

... presumably via the 12V? I'm assuming that the heating element operates at 12V rather than traction Battery voltage ... just curious! 🙂

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I’m not really sure but the whole heating/cooling system is an separate and very complex piece of kit there is no doubt some inverter or the like but for efficiency I’d assume that it would be a higher voltage. The heat pump works to about -10oC then turns on the ICE that should not worry most of us in the UK much, having said that it will probably be the coldest winter on record? There are some interesting videos on YouTube and I found the best to be “the car nut channel” part 1 is the Prius, then part 2 the RAV4. It’s located in the front right hand side of the car.

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1 hour ago, ernieb said:

...I found the best to be “the car nut channel” ...

I've found his videos very informative.  There are some interesting ones on the lubrication and cooling of the latest RAV4 2.5 litre engine.

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@PeteB, agree, he’s very much the American but I do like his videos, some of the ones that talk about customers and the things they complain about are brilliant. He appears to be very knowledgeable and well informed. 

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So I can see how the air con which requires some umpf being traction Battery powered but I have a sneaky feeling the rear defroster is 12V Battery powered. That would be interesting. 

Why not power everything off the traction Battery? Toyota already partitioning the traction Battery. Makes no odds to partition another 5 pc for other stuff and get rid of the 12V Battery?

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9 hours ago, Nick72 said:

what if i use the App to enable the rear window defrosting

Does the App actually enable rear window defrosting specifically?

As I understand - having only an 'umble HEV rather than a posh PHEV - you have an "Air conditioning system with heat pump" that you can operate remotely. I can well imaging that being run off the traction Battery, as Ernie says, to warm, cool and specifically dry the cabin. That will certainly help defog the windows. I can't see why they would necessarily run the 12V rear window de-icer while doing that.

Ernie has previously suggested that the 12V Battery is not recharged via the mains - which seems a shame but that's how it is.

And you probably could power everything directly from the traction Battery in a PHEV - if you really left the lights on for too long you could always recharge via the mains. But if you did that with a HEV you'd be totally stuck because the only way to charge the traction Battery is via the engine; and with a flat traction Battery you'd never get the engine started. So there remains 'commonality' between the HEV and PHEV in that respect.

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36 minutes ago, philip42h said:

Does the App actually enable rear window defrosting specifically?

As I understand - having only an 'umble HEV rather than a posh PHEV - you have an "Air conditioning system with heat pump" that you can operate remotely. I can well imaging that being run off the traction battery, as Ernie says, to warm, cool and specifically dry the cabin. That will certainly help defog the windows. I can't see why they would necessarily run the 12V rear window de-icer while doing that.

Ernie has previously suggested that the 12V battery is not recharged via the mains - which seems a shame but that's how it is.

And you probably could power everything directly from the traction battery in a PHEV - if you really left the lights on for too long you could always recharge via the mains. But if you did that with a HEV you'd be totally stuck because the only way to charge the traction battery is via the engine; and with a flat traction battery you'd never get the engine started. So there remains 'commonality' between the HEV and PHEV in that respect.

Can set the rear defrost, front defrost and air con seperately. 

I'll put money on the electrical heating elements being 12V and driven off the tiny Battery.

Screenshot_20210907-230715_MyT.jpg

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But remember Nick that when you initiate the preconditioning the car will fire the inverter from the traction Battery to charge the 12 volt system unless it's tethered to the charge cable when the power is taken from the connected supply. So in my case come winter I'd have mine connected to the 240 volt house supply and that would power the heating and defrost systems.  From my reading of the information available Toyota will not use the 12 volt systems unless it really has no choice.  If you use the MyT app and want to see how the charge is progressing, assuming you've requested charge now and it's in progress. the app asks if you want to wake up the car knowing that this is using the 12 volt system. I'm frankly amazed that during the tethered traction Battery charge phase that Toyota do not top up the 12 volt Battery if needed especially if say the temperature is low i.e. winter.  Anyway, that's my understanding of how it works.....

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7 hours ago, Nick72 said:

I'll put money on the electrical heating elements being 12V and driven off the tiny battery.

I won't take that bet ... I'm pretty certain that I'd lose.

As I understand, the preconditioning system will run for a maximum of 20 minutes. A heated rear screen draws around 6A (at 12V) - so in 20 minutes that amounts to 2Ah. The 'tiny' Battery isn't that tiny - reports suggest that it is between 45Ah and 52Ah depending on the AGM Battery fitted. So 2Ah is a relatively small proportion of the available charge. It is reasonable to assume that the driver will precondition the car only immediately before using it so that the 12V Battery will be recharged straight away in normal use. Clearly if the owner repeatedly preconditioned the car without using it he/she would run into problems.

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54 minutes ago, ernieb said:

But remember Nick that when you initiate the preconditioning the car will fire the inverter from the traction battery to charge the 12 volt system unless it's tethered to the charge cable when the power is taken from the connected supply. So in my case come winter I'd have mine connected to the 240 volt house supply and that would power the heating and defrost systems.  From my reading of the information available Toyota will not use the 12 volt systems unless it really has no choice.  If you use the MyT app and want to see how the charge is progressing, assuming you've requested charge now and it's in progress. the app asks if you want to wake up the car knowing that this is using the 12 volt system. I'm frankly amazed that during the tethered traction battery charge phase that Toyota do not top up the 12 volt battery if needed especially if say the temperature is low i.e. winter.  Anyway, that's my understanding of how it works.....

That doesn't feel quite right ... why do you say "when you initiate the preconditioning the car will fire the inverter from the traction Battery to charge the 12 volt system"?

I know absolutely nothing, but I could hypothesise that the heat pump operates at 240V AC. When you are plugged into the mains, it runs off the mains. When you are not tethered it uses the inverter to 'generate' a 240V supply from the traction Battery, and uses this to run the heat pump?

This would also be 'consistent' with the understanding the the car charges the 12V auxiliary Battery only when in Ready mode (and not when tethered).

But I'm only trying to construct a theory that seems consistent with the understood facts ... 😉

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2 hours ago, ernieb said:

But remember Nick that when you initiate the preconditioning the car will fire the inverter from the traction battery to charge the 12 volt system unless it's tethered to the charge cable when the power is taken from the connected supply. So in my case come winter I'd have mine connected to the 240 volt house supply and that would power the heating and defrost systems.  From my reading of the information available Toyota will not use the 12 volt systems unless it really has no choice.  If you use the MyT app and want to see how the charge is progressing, assuming you've requested charge now and it's in progress. the app asks if you want to wake up the car knowing that this is using the 12 volt system. I'm frankly amazed that during the tethered traction battery charge phase that Toyota do not top up the 12 volt battery if needed especially if say the temperature is low i.e. winter.  Anyway, that's my understanding of how it works.....

That would make a lot of sense but what I'm reading on some of the American forums is that the 12V Battery is maintained on a smart basis. Smart seemingly meaning not recharging the 12V every time your plug your car into the wall box or every time you start the key. Implications are that it monitors voltage and decides to charge. If this is true then I assume it would still be fine if I had the rear defroster running off the 12V for 20 minutes because the smart charger ought to kick in via inverter and traction Battery?

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1 hour ago, philip42h said:

I won't take that bet ... I'm pretty certain that I'd lose.

As I understand, the preconditioning system will run for a maximum of 20 minutes. A heated rear screen draws around 6A (at 12V) - so in 20 minutes that amounts to 2Ah. The 'tiny' battery isn't that tiny - reports suggest that it is between 45Ah and 52Ah depending on the AGM battery fitted. So 2Ah is a relatively small proportion of the available charge. It is reasonable to assume that the driver will precondition the car only immediately before using it so that the 12V battery will be recharged straight away in normal use. Clearly if the owner repeatedly preconditioned the car without using it he/she would run into problems.

Ah right. In which case that would mean Toyota will surely have rear defrost connected to 12V because it doesn't dent the Battery in the 20min.

 

But is the math right? Can't see where 2Ah came from. That's just me being dopey probably. Was it a third of the 6A because it is on for a third of an hour (20min)?

45Ah. That's a big Battery then. But it looks so tiny.

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27 minutes ago, Nick72 said:

Ah right. In which case that would mean Toyota will surely have rear defrost connected to 12V because it doesn't dent the battery in the 20min.

 

But is the math right? Can't see where 2Ah came from. That's just me being dopey probably. Was it a third of the 6A because it is on for a third of an hour (20min)?

45Ah. That's a big battery then. But it looks so tiny.

Yes ... the 6A for the rear screen defrost comes from Google / the Internet. I can't vouch for its accuracy but it sounds about right. 6A for 20 minutes (aka one third of an hour) amounts to a draw of 2Ah. Again, it's probably a tad more complicated than that but it's certainly of the right order. So it's hardly a killer draw over that time period.

Normal cars run the rear screen heater off the car's 12V supply - I can't see why Toyota would want to deviate from that design, nor why they'd want to introduce a secondary heating source as well.

And again yes, some folk say it's a 45Ah Battery, others 52Ah. I've seen replacements on offer between 40Ah and 55Ah, so it's something in that region. Compared with a standard 70Ah Battery in a petrol or 90Ah in a diesel it's not exactly small. Which makes me wonder that the 'issue' we have with the 'tiny' Battery maybe has less to do with it's size and more to do with the draw when the RAV 4.5 is otherwise 'off'. Who knows?

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All I can say to the above is “isn’t it all confusing”? I, like us all, got my information from various web forums, YouTube’s etc., and mashed it together in what I thought was the situation.  I guess the reality is that Toyota what ever system, voltage is being used are happy to run these electrical accessories for the 20mins defrost/ heating time.

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To add to the mix note that this diagram shows the HV Battery, bottom RH.

Also we must add into HVAC system on the PHEV the capability to heat and cool the Battery, to my mind the fitted 12v Battery would fold under the demand pressure.  When I look at the MyT app it gives a mileage for use with and without the HVAC system so type power one way or another must come from the traction Battery?

 

638F50A7-972E-45F0-AF7F-D79D62039538.jpeg

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Whilst I was looking at the Battery I took the lid off the fuse box just as a matter of interest. Wow, there some pretty hefty fuses in there, 150A with massive cables, 30 and 40A plus a host of relays. That’s something that accompanies you every time you open the door, stop etc., a wide range of clicks and clunks.

I can not find a fuse diagram for the 2021 PHEV as that will give a better idea of what is powering the front and rear defrosters. Anyone got access to the diagrams?

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I found this diagram which shows that the traction Battery 355v is connected to the HVAC system. I also found out that the main inverter/converter powers the motors at approx 650v 3 phase.

 

5454D386-3326-4851-8824-3026DF630BBC.jpeg

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... and that there is a DC/DC Converter powered by the traction Battery that supplies ~14V to the auxiliary Battery when in Ready mode. It seems reasonable to assume that the 12V circuits are then powered by the auxiliary Battery (as per a more conventional car).

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4 hours ago, philip42h said:

Yes ... the 6A for the rear screen defrost comes from Google / the Internet. I can't vouch for its accuracy but it sounds about right. 6A for 20 minutes (aka one third of an hour) amounts to a draw of 2Ah. Again, it's probably a tad more complicated than that but it's certainly of the right order. So it's hardly a killer draw over that time period.

Normal cars run the rear screen heater off the car's 12V supply - I can't see why Toyota would want to deviate from that design, nor why they'd want to introduce a secondary heating source as well.

And again yes, some folk say it's a 45Ah battery, others 52Ah. I've seen replacements on offer between 40Ah and 55Ah, so it's something in that region. Compared with a standard 70Ah battery in a petrol or 90Ah in a diesel it's not exactly small. Which makes me wonder that the 'issue' we have with the 'tiny' battery maybe has less to do with it's size and more to do with the draw when the RAV 4.5 is otherwise 'off'. Who knows?

Thanks. Makes sense. I wonder though given covid and our new ways of working if I've not used the car for over a week (and there's zero way I'm going to sit in it for an hour when in ready mode to charge the 12V battery) then apply the defrost whether I'm now taking 2 or 6Ah off something already low in charge? I'd love to see the discharge vs time curve when the car is sitting in winter noting there will be a few things drawing current when it is nominally off plus usual current leakage?

Just trying to see if I need to head something off at the pass by changing the way I use the car including my assumptions about what system is using which Battery etc.

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3 hours ago, ernieb said:

To add to the mix note that this diagram shows the HV battery, bottom RH.

Also we must add into HVAC system on the PHEV the capability to heat and cool the battery, to my mind the fitted 12v battery would fold under the demand pressure.  When I look at the MyT app it gives a mileage for use with and without the HVAC system so type power one way or another must come from the traction battery?

 

638F50A7-972E-45F0-AF7F-D79D62039538.jpeg

Agreed. Think it would fold so HVAC must be traction Battery. Like you say the EV mileage is a function of it so it has to be.

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23 minutes ago, Nick72 said:

Just trying to see if I need to head something off at the pass by changing the way I use the car including my assumptions about what system is using which battery etc.

I can't see that you would need to worry about the traction Battery - just plug it in on charge.

There's a sticky on 12V Battery maintenance:

As a rough rule of thumb, you can leave it unused for a week no problem; if you abandon it for over a month you may be chancing your arm. Best bet, if you haven't used it for two or three weeks would be to put the 12V Battery on charge - using a modern, standard smart / trickle charger (assuming that you can, of course)

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3 hours ago, philip42h said:

I can't see that you would need to worry about the traction battery - just plug it in on charge.

There's a sticky on 12V battery maintenance:

As a rough rule of thumb, you can leave it unused for a week no problem; if you abandon it for over a month you may be chancing your arm. Best bet, if you haven't used it for two or three weeks would be to put the 12V battery on charge - using a modern, standard smart / trickle charger (assuming that you can, of course)

Thanks. I'll just need to make sure I take it for a drive once a week or I'll need to be charging the 12V Battery which is a faff as that means taking it out to put it in the shed to charge it. Really feels like a backward step when my 17 or so old Corsa would start first time even after 6 weeks. 

Got me thinking. So, if the 12V Battery is dead why exactly won't the car start? I mean it goes to EV mode first in any case and when it says ready the traction Battery via inverter is charging the 12V Battery? Or is it the case (oh god please don't agree) that the car electronics are all powered off the 12V Battery and in which case a dead Battery probably means a world of pain?

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