Speculation Alert - possible Harvester Engine Choices

[Logan]

We did the math in another thread here.

Basing it on efficiency alone. If the Rivian R1S gets ~2.1miles per KW (although I've seen other reports where it was 2.4miles/kw), and the Hummer EV gets 1.6 miles per KW, I feel like a safe ballpark assumption for the Scouts is somewhere between 1.8 - 2 miles per KW.

If that consumption is at a speed of 70mph, that means in an hour, we've used ~39 kw (70 miles/1.8 miles per kw). And 39kw is ~53hp. This seems like an achievable target, even by the little 3 cylinder engine that people have been theorizing about.

For perspective the Ramcharger is using a likely much larger 3.6l V6, tuned for 130kw per hour of output (but can output as much as 190kw).

 

[Peter Hamilton]

I doubt 10kw is enough to trickle a 20% or less battery, unless you want the engine run all the time which defy the purpose of EV: a clean and quiet ride.

I think the Harvester will absolutely have to run all the time(when you put it in RE mode). I agree it defeats the purpose of an EV but it also unlocks some off grid options. Definitely not for everyone and I can't imagine using it daily.

 

[Chaparral]

I think the Harvester will absolutely have to run all the time(when you put it in RE mode). I agree it defeats the purpose of an EV but it also unlocks some off grid options. Definitely not for everyone and I can't imagine using it daily.

I think this is correct.

We are told it will get 150 miles pure Ev at that point the extender will normally kick in but we don’t know what the battery percentage will be. To get the full 500 miles we’ll almost certainly need the Harvester running right away.

I don’t conclude the RE “defeats the purpose of EV” for the following reasons.

1) The Harvester will run a small fraction of the time because almost all use will be EV only.
2) If the Harvester moves more people over to using EV and away from full gas it is an overall environmental win.
3) Unless charging from a home battery, anyone charging an EV here in California, especially after sundown, is getting power from fossil fuel power stations (natural gas), and that power is transported across a grid that loses energy to heating the conductor wires. So burning a little gas on a rare occasion in the Harvester might not actually be any worse for the environment, especially if we normally charge the battery during the day when the grid is mostly powered by solar.
4) The Harvester version has a smaller battery. That reduces the environmental impact of producing/recycling/disposal of lithium battery cells!

There are obviously many other factors. The factors are very hard to weigh against each other, and this is an issue where you can run into information that is heavily biased. I’ll hold off from forming a firm opinion but it seems to me that the Harvester could actually be a big environmental win.

 

[dearbulls]

We did the math in another thread here.

Basing it on efficiency alone. If the Rivian R1S gets ~2.1miles per KW (although I've seen other reports where it was 2.4miles/kw), and the Hummer EV gets 1.6 miles per KW, I feel like a safe ballpark assumption for the Scouts is somewhere between 1.8 - 2 miles per KW.

If that consumption is at a speed of 70mph, that means in an hour, we've used ~39 kw (70 miles/1.8 miles per kw). And 39kw is ~53hp. This seems like an achievable target, even by the little 3 cylinder engine that people have been theorizing about.

For perspective the Ramcharger is using a likely much larger 3.6l V6, tuned for 130kw per hour of output (but can output as much as 190kw).

You are mixing kw and kwh. What you said most like mi/kw, should be mi/kwh. Kw and kwh are 2 totally different things.

Kw is power output at a certain point of time, and kwh is how much energy it stored, or used over certain time.

 

[ID_ENG]

Not yet.

We will discuss the range extender more extensively as development continues, and we are ready to give more definitive answers. I have lots of my own questions as well.

Our goal is to share as much as we can with all of you on this road to production. I personally think the range extender and the engineering and tech behind it will be really interesting, especially in all the use cases.

Meanwhile some healthy debate is good. Keep the feedback coming and let's avoid slinging too many arrows if we can.

Jamie

A non answer, answer. Like an arrow to my knee.

I figured these details aren't available yet. Appreciate the reaponse.

 

[Logan]

You are mixing kw and kwh. What you said most like mi/kw, should be mi/kwh. Kw and kwh are 2 totally different things

Its totally possible that I am. I know (or thought I knew) the difference between KW (a volume of energy), and KW/H (a rate). Could you please explain what I'm missing?

But I'm fairly certain the data I have is correct in terms of consumption for the Rivian and Hummer. You can see here the reviews for the Rivian HERE, and here.

Large Pack, Dual Motor:
308.3 Miles (driven)
128.2 KWH Used
2.41 Mi/KWH

So in this case, the Rivian goes 2.41miles per KW of energy in the batteries, at 70mph. If they drove for an hour at 70mph, they'd then go 70 miles, and have used ~29KW (not KW/H) of energy (70miles/2.41 kw per mile = 29KW).

For a generator to be able to keep up with the discharge rate there, then the rate would have to be at least 29KW/H. This is the same as an engine generating ~39hp over the course of an hour.

If we assume the Scouts have less efficiency than the Rivian, but better than the Hummer, then it seems like for the same scenario it would be somewhere in the ballpark of 70 miles/1.8 miles per kw = ~39kw of energy used in an hour. And therefore a generator would need to be able to generate at least 39KW/H to keep up with the discharge rate. And that works out to ~53HP worth of output, for an hour?

That math tracks right? Or what am I doing wrong here?

 

[Peter Hamilton]

Its totally possible that I am. I know (or thought I knew) the difference between KW (a volume of energy), and KW/H (a rate). Could you please explain what I'm missing?

But I'm fairly certain the data I have is correct in terms of consumption for the Rivian and Hummer. You can see here the reviews for the Rivian HERE, and here.

Large Pack, Dual Motor:
308.3 Miles (driven)
128.2 KWH Used
2.41 Mi/KWH

So in this case, the Rivian goes 2.41miles per KW of energy in the batteries, at 70mph. If they drove for an hour at 70mph, they'd then go 70 miles, and have used ~29KW (not KW/H) of energy (70miles/2.41 kw per mile = 29KW).

For a generator to be able to keep up with the discharge rate there, then the rate would have to be at least 29KW/H. This is the same as an engine generating ~39hp over the course of an hour.

If we assume the Scouts have less efficiency than the Rivian, but better than the Hummer, then it seems like for the same scenario it would be somewhere in the ballpark of 70 miles/1.8 miles per kw = ~39kw of energy used in an hour. And therefore a generator would need to be able to generate at least 39KW/H to keep up with the discharge rate. And that works out to ~53HP worth of output, for an hour?

That math tracks right? Or what am I doing wrong here?

Added: watt or kw is the about of power a load(motor) requires. kwh is capacity to power a load of a given size for an hour. So kwh is the unit of storage for a battery meaning it could power 120kw load for an hour. The discharge rate is variable so if the load only needs 30kw then the battery can last a lot longer than an hour(4hours!).

They go 2.4 miles per kwh at 70 mph. That would take them about 2 minutes to spend one kwh. If they drive 70 miles they have used about 29 kwh and if they have a 120kwh battery they used about 25% of their battery. The kw pulled by the motor will vary based on hills, drag etc but it averages out to 29kw over an hour.

Mostly your math checks out, couple places the units are mislabeled. I am not sure about the conversion from watts to hp. There is a good deal of energy loss charging a battery due to heat so you would have to step-up the generator to maybe 50+kw. Harvester is not going to be a 50kw generator. If it was it would be the most inefficient ICE vehicle on the road...

 

[CarTechGeek]

My vote:

Compact, efficient, high power density, and demonstrated to work.

Our Technology – INNengine

innengine.com

Zero chance they are going to use some weird experimental engine.

Also high power density is usually NOT a target for Generators. High power density = higher stress.

They will want something proven reliable, and running way below peak power, so it isn't stressed when run constantly at specified full load.

 

[CarTechGeek]

I don’t believe the engine will provide any power to the drivetrain. It is a generator, running on gas, that outputs electricity to charge the battery pack.

It's commonly stated that way, but the LAST thing you want to do with your generator, is charge the batteries.

The Generator output (KW) will feed directly to the traction motors.

Charging the battery first, would just be more losses. You loses efficiency charging/discharging, when it could just be directly fed to the motors, and skip those conversion losses.

 

[CarTechGeek]

Yes! It needs to at least be able to safely accelerate you to merge into a highway. I'm not talking about full battery performance, but it needs to be more than 130kw for this potentially 8k+ lbs vehicle on 35s

No. They will always maintain enough buffer to cover short bursts of acceleration. It's EXTREMELY unlikely they will have a 130KW RE Engine.

 

[Logan]

They go 2.4 miles per kwh at 70 mph. That would take them about 2 minutes to spend one kwh. If they drive 70 miles they have used about 29 kwh and if they have a 120kwh battery they used about 25% of their battery. The kw pulled by the motor will vary based on hills, drag etc but it averages out to 29kw over an hour.

Mostly your math checks out, couple places the units are mislabeled. I am not sure about the conversion from watts to hp. There is a good deal of energy loss charging a battery due to heat so you would have to step-up the generator to maybe 50+kw. Harvester is not going to be a 50kw generator. If it was it would be the most inefficient ICE vehicle on the road...

Yes, I had some mislabled units in the first post, but glad that the math generally checks out.

For the KW to HP conversion, I just used converters online like this one.

But you're right, there is some additional inefficiencies in charging a quick search says 12-15% energy lost in charging. So you'd have to scale the power output of the generator to account for the NET needs of the vehicle, not the gross needs.

Meaning the Rivian would be 29kw of NET energy in an hour. So 29KW/H x 1.15 to account for the 15% energy loss in charging would need a generator of producing a net ~33KW/H of energy.

So a Scout with a hypothetical 1.8 KW per mile consumption at 70mph would need a ~61HP generator (39KW x 1.15 = ~45kw. 45KW = ~61hp).

I do disagree with the last statement you said though. A 50kw generator would not make it the least efficient vehicle on the road, at all, or even by a long shot. I mean, the Ramcharger is going to use a 130kw generator (a 3.6L V6 running very detuned). So that would be ~almost 3x less efficient if that was the case. And then most combustion vehicles on the road are using ~150-300hp engines. I know they aren't running at maximum output on the highway for most of them, but then again ~61hp to move a 4-8k lb SUV/Truck through the air at 70mph, isn't inefficient in my mind.

 

[Peter Hamilton]

Yes, I had some mislabled units in the first post, but glad that the math generally checks out.

For the KW to HP conversion, I just used converters online like this one.

View attachment 3514

But you're right, there is some additional inefficiencies in charging a quick search says 12-15% energy lost in charging. So you'd have to scale the power output of the generator to account for the NET needs of the vehicle, not the gross needs.

Meaning the Rivian would be 29kw of NET energy in an hour. So 29KW/H x 1.15 to account for the 15% energy loss in charging would need a generator of producing a net ~33KW/H of energy.

So a Scout with a hypothetical 1.8 KW per mile consumption at 70mph would need a ~61HP generator (39KW x 1.15 = ~45kw. 45KW = ~61hp).

I do disagree with the last statement you said though. A 50kw generator would not make it the least efficient vehicle on the road, at all, or even by a long shot. I mean, the Ramcharger is going to use a 130kw generator (a 3.6L V6 running very detuned). So that would be ~almost 3x less efficient if that was the case. And then most combustion vehicles on the road are using ~150-300hp engines. I know they aren't running at maximum output on the highway for most of them, but then again ~61hp to move a 4-8k lb SUV/Truck through the air at 70mph, isn't inefficient in my mind.

It is very inefficient. An ICE engine cruising at 70mph is not making 61hp. Probably spinning at 1800rpm and sipping fuel, I am sure you can find the powerbands for those engines and do the math. But for some cars its single digits on flat highway. Granted these trucks are rolling bricks so it will be higher but definitely much less than 60.

 

[ID_ENG]

OK I think I got it.
The Harvester turns the dial to 11. Thus more power.

 

[Peter Hamilton]

OK I think I got it.
The Harvester turns the dial to 11. Thus more power.

All the knobs in the Scout should go to 11 because 11 is more than 10.

 

[CarTechGeek]

Here are the characteristics you want:

1. Small as possible, to fit behind the rear axles
2. Low Stress design. It needs to be able to 10+ hours at full rated load all day if required.
3. Dead simple and reliable.
4. Enough Power generation to run at 70MPH, or at minimum 70% of that if you start running the Generator at the beginning of a Road trip. So 30KW-40KW minimum. i3 Rex had a 25KW genset, Volt Gen2 had 55 KW genset.
5. Efficient as possible.

I don't think VW has great parts bin choices, as they depend too heavily on Turbos. Turbo's aren't a great choice for a generator. It's higher stress and higher complexity.

If Scout is truly independent, then maybe the could get an engine from anywhere. My choice would be a Toyota Atkinson Cycle Hybrid engine.

Natural Aspirated Atkinson Cycle engines are simple, reliable, efficient, and limited in power, will be low stress.

The Toyota Dynamic Force 3 Cylinder, 1.5L Atkinson cycle engine would be my choice for an RE engine.

In some forms it delivers up to 92 KW, so limited to 55KW like the Volt 1.5, it should meet all the requirments.

The only thing is you may want to tilt it to some degree for less vertical space usage. It should accommodate some degree of tilt, and it should be fairly easy to make a new oil pan, and oil pickup to accommodate greater tilt.

 

[Peter Hamilton]

Here are the characteristics you want:

1. Small as possible, to fit behind the rear axles
2. Low Stress design. It needs to be able to 10+ hours at full rated load all day if required.
3. Dead simple and reliable.
4. Enough Power generation to run at 70MPH, or at minimum 70% of that if you start running the Generator at the beginning of a Road trip. So 30KW-40KW minimum. i3 Rex had a 25KW genset, Volt Gen2 had 55 KW genset.
5. Efficient as possible.

I don't think VW has great parts bin choices, as they depend too heavily on Turbos. Turbo's aren't a great choice for a generator. It's higher stress and higher complexity.

If Scout is truly independent, then maybe the could get an engine from anywhere. My choice would be a Toyota Atkinson Cycle Hybrid engine.

Natural Aspirated Atkinson Cycle engines are simple, reliable, efficient, and limited in power, will be low stress.

The Toyota Dynamic Force 3 Cylinder, 1.5L Atkinson cycle engine would be my choice for an RE engine.

In some forms it delivers up to 92 KW, so limited to 55KW like the Volt 1.5, it should meet all the requirments.

The only thing is you may want to tilt it to some degree for less vertical space usage. It should accomodate some degree of tilt, and it should be fairly easy to make sure new oil pan and oil pickup for greater tilt.

My preference would be something much smaller and keep battery packs large. All it needs to do is contribute maybe 30% of the cruising load to extend the range to 500.

 

[Logan]

Here are the characteristics you want:

1. Small as possible, to fit behind the rear axles
2. Low Stress design. It needs to be able to 10+ hours at full rated load all day if required.
3. Dead simple and reliable.
4. Enough Power generation to run at 70MPH, or at minimum 70% of that if you start running the Generator at the beginning of a Road trip. So 30KW-40KW minimum. i3 Rex had a 25KW genset, Volt Gen2 had 55 KW genset.
5. Efficient as possible.

I don't think VW has great parts bin choices, as they depend too heavily on Turbos. Turbo's aren't a great choice for a generator. It's higher stress and higher complexity.

If Scout is truly independent, then maybe the could get an engine from anywhere. My choice would be a Toyota Atkinson Cycle Hybrid engine.

Natural Aspirated Atkinson Cycle engines are simple, reliable, efficient, and limited in power, will be low stress.

The Toyota Dynamic Force 3 Cylinder, 1.5L Atkinson cycle engine would be my choice for an RE engine.

In some forms it delivers up to 92 KW, so limited to 55KW like the Volt 1.5, it should meet all the requirments.

The only thing is you may want to tilt it to some degree for less vertical space usage. It should accommodate some degree of tilt, and it should be fairly easy to make a new oil pan, and oil pickup to accommodate greater tilt.

This more closely aligns with what I have been envisioning.

I would personally be surprised if we see a generator as small as the i3 REX had, as even that small vehicle was underpowered when it was reduced to using just the output from the generator, and the Scouts are much larger vehicles.

My preference would be something much smaller and keep battery packs large. All it needs to do is contribute maybe 30% of the cruising load to extend the range to 500.

We already know that the EV only range is ~150 miles for the Harvester, which gives us a rough estimation of the battery pack size.

If we assume a ~2 miles per KW efficiency on the highway, that means it will have to have a ~75kw of effective battery pack size (which, interestingly is almost identical to what the Ram Ramcharger has spec'd. Its 92KW gross, but ~76kw effective).

This also means that the total energy expenditure to reach 500 miles would be 250kw (if we are assuming 2 miles per kw still, to make the math easy). So that means that the generator will have to be able to supply the other 175kw of energy (250kw total energy required - 75kw of useable battery == 175kw of energy from the generator).

The question really becomes is the design target to get 500 miles of range when the battery drops to zero (because the generator cannot keep up with demand) OR if the design intends the generator to keep up with energy demands, and therefore reaches its 500mile range when the gas tank of the generator runs out.

The BMW i3 REX was using strategy #1. And the Ram has already said that they will will use strategy #2 on the Ramcharger, which is why they're using a 130-190kw engine.

Again, personally I'm thinking (wishing?) the most likely scenario is closer to strategy #2. But we don't know, and likely won't for a while which strategy they are going to use. There really aren't many data points for what a "normal" EREV functions like afaik.

 

[CarTechGeek]

My preference would be something much smaller and keep battery packs large. All it needs to do is contribute maybe 30% of the cruising load to extend the range to 500.

They already indicated the target battery range for the Harvester is 150 miles.

Everyone wants something different, so they will want to please the majority, and I think the majority would be a lot happier if they could drive at highway speeds when the battery reaches it's designated exhaustion point. They could cover even more people, if they could do that while towing, but I don't think they can get a powerful enough genset within that space for Towing while only under genset power.

 

[Peter Hamilton]

They already indicated the target battery range for the Harvester is 150 miles.

Everyone wants something different, so they will want to please the majority, and I think the majority would be a lot happier if they could drive at highway speeds when the battery reaches it's designated exhaustion point. They could cover even more people, if they could do that while towing, but I don't think they can get a powerful enough genset within that space for Towing while only under genset power.

I hadn't seen that. I've only seen that Harvester will increase the range 150 miles. I get there is a big tradeoff in weight/cost/cargo so it will be interesting to see how those tradeoffs are managed. Do you have a link to where they talk about the harvester battery range?

 

[CarTechGeek]

Do you have a link to where they talk about the harvester battery range?

https://scoutmotors.community.forum/threads/scout-traveler-faq.1080/#post-11275

I don't have a link, but IIRC, in some previous discussion of this, they mentioned that the smaller battery defrays the cost of the Range Extender.

Harvester model will have a smaller battery and Cost less than the 350 Mile range BEV only version.