12v or high voltage battery

[Barney7]

Once the car is in ready mode do the items like heated seat heated steering wheel tailgate and main heater draw there power from the HV Battery or the 12 V.

We do quite a few short journeys and in this colder weather was a bit concerned about draining the 12v 

many thanks 

[philip42h]

In place of a traditional alternator, the car has a DC/DC converter to provide a 12v supply from the 355v traction Battery. This is activated once the car is in Ready mode.

Like any car, the RAV4 has a 12v loom powering many of the ancillary systems. These are powered by a combination of the DC/DC converter and the 12v auxiliary Battery. In addition, the 12v auxiliary Battery is topped-up by the DC/DC converter while the car is in Ready mode.

So, no, you won't drain the 12v battery by doing short journeys in summer or winter. 🙂

If you really want to drain the 12v auxiliary battery you could put the car into Accessory mode and use as many of the 12v systems as you can, or leave the car switch off and unused for a couple of months. But you don't want to do that ... 😉

[ernieb]

My four pennies worth, I think if your trips very, very short e.g., runs to the school 1/2 mile away and no longer trips you could be in trouble especially in very cold weather.

However, Philip has extensive knowledge of the HEV models.

[Barney7]

Thanks Philip 

great explanation.

i know that our short distances could cause a 12v issue and I’m prepared as I have a booster pack under the passenger seat and try to leave it in ready mode for as long as possible.

many thanks 

[philip42h]

33 minutes ago, ernieb said:

My four pennies worth, I think if your trips very, very short e.g., runs to the school 1/2 mile away and no longer trips you could be in trouble especially in very cold weather.

However, Philip has extensive knowledge of the HEV models.

That's just dinosaur thinking Ernie ... 😉

With a traditional ICE, probably the most significant drain on the 12v system is the starter motor which draws 10s if not 100s amps for several seconds while turning the engine over to start it. And then the alternator needs to be run for several miles just to replace the power used - 10s of miles if all the 12v systems are active on a cold day. So there is ingrained thinking that short runs on cold days are 'bad'.

In this respect the HEV and the PHEV are pretty much that same. Getting the car into Ready mode will draw no more than an amp or so and for rather fewer seconds than it would take to turn a starter motor. So the actual draw on the 12v auxiliary Battery is small. And as soon as the car is in Ready mode, the DC/DC converter sets about topping-up the auxiliary Battery from the traction Battery. All the 12v systems are then run from the DC/DC converter and the traction battery so there is a greater draw on the traction battery in cold weather but the 12v auxiliary battery won't be significantly impacted.

Where the PHEV and the HEV differ is in traction battery capacity. You are likely to have a fully charge 'fat' battery that can trivially accommodate the demand to top-up the auxiliary battery. With my HEV, which is parked in the garage, on a warm day when I have been using the car regularly I can reverse all the way out of the garage, put the car into drive and set off before the ICE fires up. On a cold winter's day the ICE will fire before I've taken my foot off the brake pedal to reverse out of the garage ... noting here that reverse motion is accomplished using electric motors only - the ICE has no reverse gear.

[ernieb]

Well Philip, I’m probably old enough to be a dinosaur 🦕 😇.

My next door neighbour regularly discharges her 12v Battery by running to the school up the road, stops, starts then runs back four times a day (two schools different times) They are getting a Tesla Y model tomorrow hopefully  they will remember to keep it plugged in?

[philip42h]

34 minutes ago, ernieb said:

Well Philip, I’m probably old enough to be a dinosaur 🦕 😇.

My next door neighbour regularly discharges her 12v battery by running to the school up the road, stops, starts then runs back four times a day (two schools different times) They are getting a Tesla Y model tomorrow hopefully  they will remember to keep it plugged in?

You and me both Ernie ... 🙂

As to your neighbour, I can't possibly know, but perhaps she sits waiting for the kids to come out in Accessory mode to avoid having that irritating ICE running with all the electrics on? Who knows ... 

[Barney7]

1 hour ago, philip42h said:

That's just dinosaur thinking Ernie ... 😉

With a traditional ICE, probably the most significant drain on the 12v system is the starter motor which draws 10s if not 100s amps for several seconds while turning the engine over to start it. And then the alternator needs to be run for several miles just to replace the power used - 10s of miles if all the 12v systems are active on a cold day. So there is ingrained thinking that short runs on cold days are 'bad'.

In this respect the HEV and the PHEV are pretty much that same. Getting the car into Ready mode will draw no more than an amp or so and for rather fewer seconds than it would take to turn a starter motor. So the actual draw on the 12v auxiliary battery is small. And as soon as the car is in Ready mode, the DC/DC converter sets about topping-up the auxiliary battery from the traction battery. All the 12v systems are then run from the DC/DC converter and the traction battery so there is a greater draw on the traction battery in cold weather but the 12v auxiliary battery won't be significantly impacted.

Where the PHEV and the HEV differ is in traction battery capacity. You are likely to have a fully charge 'fat' battery that can trivially accommodate the demand to top-up the auxiliary battery. With my HEV, which is parked in the garage, on a warm day when I have been using the car regularly I can reverse all the way out of the garage, put the car into drive and set off before the ICE fires up. On a cold winter's day the ICE will fire before I've taken my foot off the brake pedal to reverse out of the garage ... noting here that reverse motion is accomplished using electric motors only - the ICE has no reverse gear.

Brilliant explanation 

[mobi]

Is there any way driver can force ICE to run rather than car deciding when to turn it on?

 

[ernieb]

Charge mode button will do it with the PHEV.

[philip42h]

1 hour ago, mobi said:

Is there any way driver can force ICE to run rather than car deciding when to turn it on?

1 hour ago, ernieb said:

Charge mode button will do it with the PHEV.

... and such a button would be wholly redundant on the HEV ... 😉

[Terry10]

Slightly off topic I have a question. So with my HEV I regularly get home and select EV mode and reverse up my 1 in 4 drive with no problem at all. If there isn't enough power to do this the car just plain refuses and ice fires up.

Is there any problem or long term risk of damage with what I am doing??
regards Terry.

[philip42h]

4 minutes ago, Terry10 said:

Slightly off topic I have a question. So with my HEV I regularly get home and select EV mode and reverse up my 1 in 4 drive with no problem at all. If there isn't enough power to do this the car just plain refuses and ice fires up.

Is there any problem or long term risk of damage with what I am doing??
regards Terry.

No, I shouldn't' have thought so ... if you have sufficient charge in the traction Battery it will get you up; if you haven't the car has the run the ICE to generate the necessary electricity.

[Cyker]

Agreed; This is part of what it was designed to do so I don't know why you'd think it would cause any damage...??

As long as you don't try to reverse faster than MG1 can counter-spin against the ICE you'll be okay.

 

7 hours ago, philip42h said:

... and such a button would be wholly redundant on the HEV ... 😉

I very much disagree! If there was an option to change the EV Mode button for, like, a Charge button on my Yaris I'd take it in a heartbeat!!

It would be so useful for occasions when I know I'm going to be stuck in traffic for ages - Could just force the car to charge the traction Battery in advance, and then let it sit with the engine off while I'm crawling through traffic at 3mph.

At the moment, the car has extremely bad timing, and will run on MG2 in free flowing traffic, and deplete the Battery just in time for the traffic jam, so I end up losing mpgs while it sits there acting like a very inefficient generator, and it will finish charging the Battery up to 4 bars just as the traffic starts moving, and switch back to MG2 just long enough for it to deplete back to 3 bars as I hit stationary traffic again. It drives me mad!!

If I could force it to charge up to 5 or 6 bars in advance in the free-flowing traffic instead it would be much more efficient and far less obnoxious!

The EV-mode button on the other hand is a waste of a perfectly good button; It's literally useless in the Mk4 as it only has a 700watt battery, which isn't enough for it to drive any useful distance in EV mode only, and since it also never seems to let you use it immediately when the cars just been turned on (Unlike e.g. the Auris, where it actually is useful), it's not even useful for shuffling around parking spaces or some short distance thing like that!

That is one of two options I wish the car had; A Charge button and the ability to stop the car from turning on the ICE when the heating is set too high. I just want it to use whatever engine heat there is, not waste fuel as a very inefficient heater trying to reach a temperature it can't actually reach! It's something that annoys me as none of my previous cars would do this! To be fair those had normal heater controls and not fancy climate control, but I liked those better...

[TonyFR]

I had a drained 12v Battery problem in the summer (described among the lengthy series of posts elsewhere in the 12v Battery maintenance topic). I now realise that it happened because I was using Accessory mode for long sessions doing route planning etc. I was in the ingrained habit of "turning off the engine" - years of traditional ICE driving - to do anything if I wasn't actually moving. I now realise that it's always best to be in Ready mode, when the 12v Battery is always being taken care of by Big Brother traction battery and in extremis by the ICE.

[ernieb]

9 hours ago, TonyFR said:

I had a drained 12v battery problem in the summer (described among the lengthy series of posts elsewhere in the 12v battery maintenance topic). I now realise that it happened because I was using Accessory mode for long sessions doing route planning etc. I was in the ingrained habit of "turning off the engine" - years of traditional ICE driving - to do anything if I wasn't actually moving. I now realise that it's always best to be in Ready mode, when the 12v battery is always being taken care of by Big Brother traction battery and in extremis by the ICE.

It's always difficult to break the habits of a lifetime, the need to be in READY mode for many would be counter intuitive. 

[mobi]

11 hours ago, TonyFR said:

 I was in the ingrained habit of "turning off the engine" - years of traditional ICE driving - to do anything if I wasn't actually moving

In my ICE car if I do this (and I do this often) after sometime a warning message appears asking me to turn on engine to prevent Battery going flat. 

Surely Toyota can program such message? All it takes to insert a line of code to check Battery condition and if accessory mode is on for a preset time. 

 

[Roy124]

On both Corolla and Yaris Cross, and my E220 before that, Accessory mode shuts after 15 minutes or so. 

[Trewithy]

When I wash my car I always leave it in ready mode to get the 12v Battery topped up.  When the HV Battery starts to get low the engine will start in order to put some charge back into the HV Battery.  In an hour the ICE will start 2 or 3 times running for about 3 minutes each time.

[mobi]

On 12/12/2022 at 2:18 PM, philip42h said:

... and such a button would be wholly redundant on the HEV ... 😉

The USA version of RAV4 does have that button. 

You can see that at 5:16 in this video

It also has paddle shifters. 

[Strangely Brown]

The prime is PHEV, not HEV.
There is a handy Badge on the fender (wing).

[philip42h]

25 minutes ago, mobi said:

It also has paddle shifters. 

The GR Sport HEV (2023 replacement for the Dynamic) features paddle shifts ... 😉

[Strangely Brown]

1 minute ago, philip42h said:

The GR Sport HEV (2023 replacement for the Dynamic) features paddle shifts ... 😉

I'd say that is a triumph of marketing over any actual benefit. It's still a CVT. ¯\_(ツ)_/¯

[philip42h]

8 minutes ago, Strangely Brown said:

I'd say that is a triumph of marketing over any actual benefit. It's still a CVT. ¯\_(ツ)_/¯

... and I'd wholeheartedly agree - but some folk think paddle shifts important ... 😁

[mobi]

12 hours ago, Strangely Brown said:

The prime is PHEV, not HEV.
There is a handy badge on the fender (wing).

How does it matter? PHEV = HEV with bigger Battery

There is technically no reason why same features can't be added in HEVs. 

BTW, UK/European PHEVs don't get those features.