ICE mode on HEV

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Tue 28 Jun 2022 18:32
ICE mode on HEV - movilogo

The HEVs typically have EV mode [uses motor if battery has enough charge] or auto mode [where car decides combination of ICE and EV modes].

But HEVs usually don't have dedicated ICE only mode where user decides whether to use EV mode or not.

Why is that?

Having said that, I watched a video of new Kia Niro where it is said that sports mode switches to ICE always on mode and digital display shows a true rev counter instead of typical EV power dial in this mode.

Technically it should be designed so that ICE mode can perform entirely independent of HEV modes. Most HEVs malfunction if traction battery discharges completely.

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Tue 28 Jun 2022 18:59
ICE mode on HEV - Adampr

I think the battery's too small for it to be of any use.

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Tue 28 Jun 2022 19:54
ICE mode on HEV - badbusdriver

But HEVs usually don't have dedicated ICE only mode where user decides whether to use EV mode or not.

Why is that?

Wouldn't that defeat the point?.

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Tue 28 Jun 2022 20:03
ICE mode on HEV - Adampr

I completely misunderstood the question in my previous post. Yes, why would you want to switch off the bit that saves you fuel?

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Tue 28 Jun 2022 20:45
ICE mode on HEV - RichT54

The transmission in my Hybrid Jazz would have to be totally redesigned as the gear ratios for the three different modes of operation (pure electric, ICE+electric, pure ICE) are all fixed. The result being that pure ICE mode is only available over a certain speed (47 mph?). There is no way you would be able to pull away from a standstill on the ICE alone, even if it would let you try.

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Tue 28 Jun 2022 21:12
ICE mode on HEV - Brit_in_Germany

I think that must be wrong or you would be stuck at the traffic lights if the battery was empty.

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Tue 28 Jun 2022 21:15
ICE mode on HEV - dan86

I think that must be wrong or you would be stuck at the traffic lights if the battery was empty.

I don't think the battery ever allows itself to get that empty

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Tue 28 Jun 2022 21:27
ICE mode on HEV - RichT54

I think that must be wrong or you would be stuck at the traffic lights if the battery was empty.

There is a very thorough video which explains how the Honda hybrid system works:

https://www.youtube.com/watch?v=QLUIExAnNcE

The one that he describes is for the CR-V, but it is essentially the same as that used by all current Honda hybrids. The video shows how in ICE-only mode, a clutch automatically connects the engine crankshaft through some fixed gearing to the differential. Because it is a fixed ratio, you are limited to what road speeds it can be used for.

In normal operation, the clutch would not be engaged and the ICE would only recharge the battery as required. However, if the ICE stopped running, eventually there would not be enough power in the battery to propel the car and you would indeed be stuck.

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Tue 28 Jun 2022 21:14
ICE mode on HEV - Sofa Spud

Suppose one's driving to London, for example. One might want to save the battery for the city part of the trip so that one can drive in EV mode once there, and use the engine for the drive up to the edge of London.

That's the only reason I could think of for needing an 'engine only' mode - except perhaps as a get-you home in an emergency. If the engine and electric motor can both be used separately, if one system fails you can still drive.

Edited by Sofa Spud on 28/06/2022 at 21:18

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Tue 28 Jun 2022 21:25
ICE mode on HEV - movilogo

Yes, having the choice, the driver can maximise EV when necessary. For example making sure always using ICE on motorways to ensure inside city EV mode is always available.

Also, if hybrid system malfunctions then one can simply use the car as ICE only mode.

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Tue 28 Jun 2022 21:41
ICE mode on HEV - mcb100
‘Suppose one's driving to London, for example. One might want to save the battery for the city part of the trip so that one can drive in EV mode once there, and use the engine for the drive up to the edge of London.’
A plug-in hybrid will give you that option - at least the recent Stellantis ones I’ve driven do. It takes about an hour to charge the traction battery from fully discharged to fully charged, during which time the fuel consumption is fairly catastrophic…

Edited by mcb100 on 28/06/2022 at 21:42

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Tue 28 Jun 2022 21:56
ICE mode on HEV - RichT54

Suppose one's driving to London, for example. One might want to save the battery for the city part of the trip so that one can drive in EV mode once there, and use the engine for the drive up to the edge of London.

The range of a hybrid in EV mode is much less than for a pure electric vehicle. If I start with a full battery in my Jazz, I would only travel about 1 - 3 miles before the ICE has to start. The economy from a hybrid comes from multiple cycles of charging/discharging and of course regenerative braking. You would need a much bigger battery to get a useful range on pure electric mode.

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Tue 28 Jun 2022 21:38
ICE mode on HEV - mcb100
The Atkinson cycle IC engines are designed to work alongside the electrical systems, not to run as standalone power units. And so torque curves are not optimised for petrol only use.
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Wed 29 Jun 2022 09:58
ICE mode on HEV - Terry W

Electric motors provide maximum torque at any speed so do not need a gearbox.

ICE needs a gearbox to enable the engine to function at slow speeds.

The could be two ways of combining an electric and ICE motor:

  • ICE drives a generator, electric motor drives the car at slow speeds. Without a gearbox (cheaper) the ICE can only kick in when road speed is sufficient for the ICE to run at acceptable RPM
  • ICE and electric motor work together and when batteries depleted the ICE will work independently. This needs an expensive auto gearbox

Ultimately it is a matter of economics, design and resilience wich solution is chosen.

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Wed 29 Jun 2022 12:24
ICE mode on HEV - movilogo

Since HEVs can travel very short distance (under 2 miles) as pure EV, for someone who mostly travel on motorways at high speeds, what is the advantage?

I can see some advantage where someone crawling in heavy traffic as ICE can be switched off and car can crawl as pure EV.

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Wed 29 Jun 2022 12:54
ICE mode on HEV - RT

Since HEVs can travel very short distance (under 2 miles) as pure EV, for someone who mostly travel on motorways at high speeds, what is the advantage?

I can see some advantage where someone crawling in heavy traffic as ICE can be switched off and car can crawl as pure EV.

Even on motorways, you'll still need to accelerate to start with and brake at the end - brake regeneration on any hybrid will recover some of that wasted energy and supplement acceleration, thus saving fuel.

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Wed 29 Jun 2022 13:13
ICE mode on HEV - Terry W

Urban driving may provide some regeneration.

On a motorway it will be completely trivial - possibly brake once in 100miles or more. The increased weight and complexity may completely negate any benefit.

What I find more interesting as a proposition is fitting a smaller, lighter ICE tuned for economy with the battery used to supplement acceleration.

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Wed 29 Jun 2022 13:14
ICE mode on HEV - Adampr

They call that a 'mild hybrid'. They don't seem to be hugely popular.

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Wed 29 Jun 2022 13:47
ICE mode on HEV - mcb100
A mild hybrid won’t run solely on electric - the battery and motor are there to provide assistance to the petrol engine when setting off, accelerating.
A full hybrid - Toyota Prius, etc, Honda CR-V - will cover possibly a couple of miles in EV mode.
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Wed 29 Jun 2022 15:17
ICE mode on HEV - Adampr
A mild hybrid won’t run solely on electric - the battery and motor are there to provide assistance to the petrol engine when setting off, accelerating. A full hybrid - Toyota Prius, etc, Honda CR-V - will cover possibly a couple of miles in EV mode.

I was replying to Terry W's comment on having economical ICEs boosted by an electric engineer. Confusing thread, this one

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Wed 29 Jun 2022 13:54
ICE mode on HEV - craig-pd130

Last time I checked, all BMW PHEVs had a 'save battery' mode in which the ICE runs all the time and the electric traction motor is not used, to conserve battery power for ULEZs and / or to top up the battery.

My 225xe certainly had that mode.

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Wed 29 Jun 2022 15:16
ICE mode on HEV - Adampr

Last time I checked, all BMW PHEVs had a 'save battery' mode in which the ICE runs all the time and the electric traction motor is not used, to conserve battery power for ULEZs and / or to top up the battery.

My 225xe certainly had that mode.

Yeah, but that's a PHEV, I think we're talking about 'self-charging' hybrids here.

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Wed 29 Jun 2022 15:37
ICE mode on HEV - movilogo

Do the mild hybrids help consumer any way? I thought manufacturers were forced to introduce them else government would penalize them via punitive taxes for not complying with environmental regulations.

The advantage of mild hybrid is miniscule but one more thing to go wrong outside of warranty period. Typically mild hybrid battery is kept at boot, taking away the space for spare wheel.

Atkinson cycle could be an issue to drive cars directly. Based on my internet reading, the Otto cycle ICE typically produces more torque and power - albeit using bit more fuel.

Whether ICE can be offered as standalone mode in HEVs depend on how the transmission is designed. Toyota uses ICE + MG1 + MG2 combination rotating at different speeds to provide gear ratios - hence it is known as eCVT which is not traditional CVT.

Kia uses DCT (though latest Sportage HEV uses Torque Converter) where input from ICE and motor are merged. Technically this transmission may be able to run in ICE mode only. This may explain why Kia can offer (at least in latest Niro) forced ICE on mode.

IIRC Honda's latest HEVs works like railway locomotives, where ICE works as generator, which in turn runs the motor - thus eliminating need for any gearbox.

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Wed 29 Jun 2022 15:48
ICE mode on HEV - Adampr

Still not clear on why you would want to turn off the electric bit. It's already in the car and it gets its energy from braking so costs you nothing to use.

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Wed 29 Jun 2022 16:25
ICE mode on HEV - movilogo

1. Deciding when to use the EV mode - rather than car deciding of its own.

2. Have some fun with ICE by redlining it.

3. Having a functional car even if hybrid system malfunctions.

Mind you, HEV is often not a choice but compulsion. Some cars you can no longer buy in ICE only version.

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Wed 29 Jun 2022 17:37
ICE mode on HEV - badbusdriver

They call that a 'mild hybrid'. They don't seem to be hugely popular.

Not sure what your evidence is for this statement?.

Going by the general comments on the forum, most seem to be very sceptical of the benefits afforded by a mild hybrid and so maybe don't actually want them. But the simple fact is that the majority of new cars currently on sale in the UK which are have a petrol engine but are neither HEV or PHEV will be using a mild hybrid (MHEV) setup.

Do the mild hybrids help consumer any way? I thought manufacturers were forced to introduce them else government would penalize them via punitive taxes for not complying with environmental regulations.

The advantage of mild hybrid is miniscule but one more thing to go wrong outside of warranty period. Typically mild hybrid battery is kept at boot, taking away the space for spare wheel.

As with any hybrid, the amount of fuel saved by a MHEV will be determined by how you drive. But as an example of what is possible, What Car recorded an average economy figure around 15% higher for the MHEV Suzuki Ignis over the solely ICE version in an identical real world MPG test. Not a massive advantage granted, but hardly miniscule.

As for the battery placement being the reason a spare wheel can't be carried, if that is the case(*), then it is due to lazy design rather than necessity. The battery on a typical (for a small car) MHEV is not very big, so doesn't need much space. Nor is it very heavy, though obviously there is more to a mild hybrid system than just the battery. But as an example, the entire mild hybrid system on a Suzuki Swift (* the battery on the Swift is under the floor) adds 25kg to the total weight of the car.

Edited by badbusdriver on 29/06/2022 at 17:38

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Wed 29 Jun 2022 19:21
ICE mode on HEV - Adampr

I mean not very popular with buyers, rather than with manufacturers. A few of them are marketed as 'hybrid' and I think people are disappointed when they discover it never switches to EV.

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Wed 29 Jun 2022 19:39
ICE mode on HEV - badbusdriver

I mean not very popular with buyers, rather than with manufacturers. A few of them are marketed as 'hybrid' and I think people are disappointed when they discover it never switches to EV.

While I would agree that there will inevitably be some folk who see the word hybrid in the title and leap to incorrect assumptions based on that, I'd guess those to be very much in the minority.

I'm not convinced the majority of buyers care would care enough to form an opinion on MHEV's one way or the other. They see a car they want, and if it only comes as a MHEV, so be it. Doesn't make any difference to them unless it has to be plugged in.

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Wed 29 Jun 2022 19:28
ICE mode on HEV - Adampr

1. Deciding when to use the EV mode - rather than car deciding of its own.

2. Have some fun with ICE by redlining it.

3. Having a functional car even if hybrid system malfunctions.

Mind you, HEV is often not a choice but compulsion. Some cars you can no longer buy in ICE only version.

1. You would get next to no range. EV operates whenever it can and doing so is of no detriment. 2. The ICE isn't really set up for fun. It would be very sluggish at low revs and you'd struggle to redline it as it will be on an auto, probably CVT, gearbox. 3. Most, if not all, hybrids will run if the electric motor fails. They will just be slow and rough
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Wed 29 Jun 2022 20:32
ICE mode on HEV - sammy1

Battery range on EVs improving all the time. I can see any combination of ICE and a battery becoming obsolete with big bills for these as they get older. I will hang on to our ICE for a few years yet. There will be areas of the world where an EV will never be practical

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Wed 29 Jun 2022 20:53
ICE mode on HEV - badbusdriver

I can see any combination of ICE and a battery becoming obsolete with big bills for these as they get older.

Hybrids have been around since the turn of the millennium and in the case of Toyota, Lexus and Honda, are amongst the most reliable cars on the road irrespective of what powers the wheels. Plenty of examples have clocked absolutely huge mileages with nothing more than routine servicing. And because the battery on a self charge hybrid isn't that big, it doesn't actually cost that much to replace them.

There will be areas of the world where an EV will never be practical

Yes, but unless you plan to move to one of them, I'm not sure why that fact would be relevant?.

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