Speculation Alert - possible Harvester Engine Choices

[Gurble]

Why you ask? Great question... It's simple.

Because the Harvester motor will be quite small relative to the size of the battery pack and small relative to the size of the truck and its curb weight. And, if you go by CarTEchGeek and the i3 example, then you are essentially using a scooter battery (34 HP) to send power to a motor directly. Yes, 34 HP!

This is also why Scout has a stake in the sand and has stated a 500 mi estimated RANGE for these vehicles (which is absolutely phenomenal BTW). All the naysayers wants to be able to drive for 15 hours straight without stopping for gas or energy. Why they want to do this type of torturous driving, I dunno. That's not for me, and I am perfectly happy to stop, charge, pee and eat while road tripping. Right now there is not a nuclear-optioned Scout to drive for ever.

Now, if you want to take away the EV benefits (including HP, instantaneous TORQUE and all of the additional storage space Scout has planned for everyone), then you could put a giant V6 in the frunk and build a RAM and pretend its an EV. Or you could put a Scooter motor in and skip the whole battery thing.

Even if you went full MAD MAX and filled the bed with all the gas from GAS TOWN, you would be pulling MORE WEIGHT and you would not recoup enough energy to drive for 15 hours at HWY speeds. The truck would simply consume more than it receives from the Harvester. Again there is a stated range of 500 for a reason.
View attachment 3577

The Harvestor being a tiny motor makes it more important that it send electricity directly to the wheels not less, because that's the more efficient way to do it. Going through the battery first gives no benefit whatsoever. It only results in loss of efficiency and wear and tear on the battery.

The battery can still be used at the same time as the generator to supply more power when needed.

 

[speedrye]

Heaven only knows. Kinda wish original OP would delete it-HaHa!
No-seriously!!!

By the time we're done with this thread, we'll have fully designed the system for Scout. We're just in the brainstorming portion now. If Scout could just put some dimensions up for us of the available space (CAD drawings would be preferable), we'll handle the rest!

 

[Logan]

By the time we're done with this thread, we'll have fully designed the system for Scout. We're just in the brainstorming portion now. If Scout could just put some dimensions up for us of the available space (CAD drawings would be preferable), we'll handle the rest!

 

[MountainDad]

That article says the power comes from the diesel/generator (not batteries) and powers the traction motors, which is the idea @CarTechGeek is promoting.

Why invite electrical losses and battery wear by feeding power from the generator through the battery to get to the motors, instead of sending power directly to the motors, and anything not used by the motors then gets stored in the battery?

Obviously, this does not work if the current draw from the motors is higher than the generator can create, hence the request for a larger generator from a lot of us.

Locomotives don't always have batteries because every pound of cargo is revenue. Non-revenue generating weight is dead weight, so they have absolutely massive diesel engines. For passenger vehicles, the battery is the "tank" that needs refilling and it allows the engine to operate at its most efficient speed for turning a generator to produce electricity. If the engine was connected to a generator which was connected directly to the motors, then the demand from the throttle to the motors creates a draw from the generator, which has to create the electricity to turn the motors directly - this means the engine has to throttle up and down to enable the generator to supply the current to meet the demand (e.g., when towing uphill or clearing a difficult off-road obstacle). Then you lose optimum fuel efficiency in the engine because it will either operate below or above its most efficient range to power the generator, as well as having to have more complex emissions controls, throttle controllers, etc, all of which increase the size of the engine package and complexity of the control mechanisms.

You sacrifice convenience (being able to drive as long as you like and refill any time) for efficiency (simpler motor designed to be optimized, leading to better durability, lower fuel consumption, and lower emissions).

Directly from the experts:

The concept is simple: The vehicle runs on electricity from the battery, and when the battery is depleted or more power is needed, the gasoline engine switches on to power a generator. That produces current that goes to the battery pack, and then the wheels. The battery acts as a buffer, so the generator can operate at its most productive speeds—meaning it may not run from 600 to 6000 rpm, as an engine that powers the wheels has to.

The important part to understand is that engine torque only goes to run the generator, not turn the wheels. The engine output shaft isn't mechanically connected to the wheels; they are powered solely by one or more electric motors.

Diesel-electric railroad locomotives have used this layout for many decades, in part because it's well adapted to steady vehicle speeds, which don't have much variance in power demand. The power required by passenger road vehicles, on the other hand, may vary by an order of magnitude or more. At the low end is steady-speed cruising on flat roads; at the high end is accelerating up a steep hill to merge into traffic.

 

[MountainDad]

The Harvestor being a tiny motor makes it more important that it send electricity directly to the wheels not less, because that's the more efficient way to do it. Going through the battery first gives no benefit whatsoever. It only results in loss of efficiency and wear and tear on the battery.

The battery can still be used at the same time as the generator to supply more power when needed.

Quite the opposite.

 

[R1TVT]

From a purely architectural and thermodynamic standpoint, it could be implemented in any number of ways, which is very true. The only point I was making was that the Harvester will be small (not V6 sized, if it ain't fitting in the frunk) and will likely be larger than an i3 Scooter engine, but until we really need to know the size of that battery, and the way the Harvester will run in parallel or isolation, and we need to wait for more details. Based on the way it was "positioned" at the reveal, it will not be identical to either a RamCharger or an i3.

 

[Gurble]

... If the engine was connected to a generator which was connected directly to the motors, then the demand from the throttle to the motors creates a draw from the generator,

I don't know why this isn't getting through, but again, no one is saying that the battery won't be used. The battery can be used to supplement the power of the generator for high load demands. Why do you think that's not the case?

The battery and the generator are both connected to the motors through a common inverter/controller. The generator does not need to go "through" the battery to power the motor.

 

[Logan]

The only point I was making was that the Harvester will be small (not V6 sized, if it ain't fitting in the frunk) and will likely be larger than an i3 Scooter engine,

I think this seems like the most likely scenario.

The gap between them is fairly large (like... 3L of displacement different).

I still think something in the 1-2L size range is the most likely scenario. Based on both the theoretical efficiency we have worked out, and the resulting "average" output of the generator. But we won't know for months/years what it actually is.

The upside, is I have one reservation, and it can be changed if needed. So as long as we get data about things well in advance and can make an informed decision on if the specific implementation meets our needs or not, I'm good.

 

[R1TVT]

I don't know why this isn't getting through, but again, no one is saying that the battery won't be used. The battery can be used to supplement the power of the generator for high load demands. Why do you think that's not the case?

The battery and the generator are both connected to the motors through a common inverter/controller. The generator does not need to go "through" the battery to power the motor.

Quite simply, b/c that way isn't the ONLY way that this can be implemented, and because the Harvester will be small, and we don't know the full capacity of the battery or the output of the generator yet.

 

[dearbulls]

The term "hybrid" has a regulatory meaning.

The Harvester option could very well require classification of the vehicle as a Hybrid.

In Georgia BEV has over $212 annual special tax (and it's going up every year), it'd be great if Harvester could be categorized as PHEV. Still get full federal tax credit but pay only $20 registration each year.
Win-win

 

[dearbulls]

A "hybrid" is any vehicle with more than one source of power for propulsion. Most vehicles are parallel hybrids. Some are series hybrids. If the Harvester is not mechanically connected to the drivetrain, it IS a series hybrid. This explains the difference, though still dumbed down and incomplete:

https://www.caranddriver.com/features/a46275944/series-hybrid-vs-parallel-hybrid-explained/

I don't know how the Harvester option will be implemented and I am not an electrical propulsion engineer but I have been daily driving a series hybrid* vehicle for 10 years. These are some modes I'd expect to see that I'm familiar with from my experience. I have a 2014 Cadillac ELR (fancy Chevy Volt) that I've owned since new. It has 4 basic modes of operation: Tour, Sport, Mountain, and Hold.

Tour - This is the "normal" mode and what the car defaults to on startup. This will use only battery power until reaching a designer specified State of Charge (SOC). Basically you are full EV until the car decides to start running the engine as needed (it turns on and off) to maintain a safe SOC for normal driving - probably 10-15%.

Sport - Claims greater throttle response, stiffer suspension, etc. I probably used this once 10 years ago, didn't really notice a difference and haven't used it since. Everything has a Sport mode though. The 2016 ELR is able to combine the generator power + battery for increased output in Sport mode which would be more useful.

Mountain - This mode raises the minimum SOC to about 30% to keep extra reserve in the battery for long uphill climbs. If you are already below the ~30%, it will run the engine continuously until SOC reaches about 30%, then revert to maintaining that SOC (engine on/off as required). It is inefficient to charge the battery via the generator so it only does it in this mode to ensure there is enough reserve for an extended high use scenario.

Hold - This is driver selectable and commands the car to maintain whatever SOC it is at when it is selected. This is basically hybrid mode and is essentially what the car goes into automatically when you reach minimum SOC in Tour or Mountain mode. This lets you keep the battery at a user selected SOC. If you select it when you start a fully charged vehicle, it will keep the battery full and start running the generator off and on as needed.

I would expect to see some version of these modes + a Towing mode that has some minimum SOC >the Mountain mode 30% as the basic drive modes.

A lot of discussion about "150 mile EV range" and what that says about the battery size. MY thoughts:
-If you're coming from a pure BEV experience, the battery in an EREV is not going to be managed the same. At least it shouldn't be.
1) There is no need to allow the battery to charge up to 100%. It's bad for the battery and you have a generator for extra range.
2) The battery will never go to 0% for the same reasons. The battery is going to be kept in a SOC range of happiness.
If the generator is undersized (as it appears to be for packaging constraints), I would expect the minimum SOC for each mode to be something higher than what my ELR uses. Maybe a min SOC of 30%, Mountain mode of 50% and tow mode 75%. Those are spitball estimates for the SOC at which the generator starts.
If the full BEV battery is 350mi, then a slightly smaller version might be say, 300mi IF it were used like a BEV battery but it WON'T be. If you only charge that "300mi" battery to 80% and only let it go down to 30%, you get...150mi of EV range. The battery acts as a buffer providing extra current when needed and storing excess current from braking or going downhill once it reaches the min SOC of whatever mode it is in.

*Yes, I know the engine/generator in the ELR/Volt is capable of driving the wheels in some situations but 99+% of the time, it is just generating electricity and mechanically separated from the drivetrain as a series hybrid.

Mmm. More than 1 source, huh?

 

[Bodie]

Mmm. More than 1 source, huh?

View attachment 3583

Sure, if it has a diesel and a gas engine.

 

[oldgeeksguide]

Locomotives don't always have batteries because every pound of cargo is revenue. Non-revenue generating weight is dead weight, so they have absolutely massive diesel engines. For passenger vehicles, the battery is the "tank" that needs refilling and it allows the engine to operate at its most efficient speed for turning a generator to produce electricity. If the engine was connected to a generator which was connected directly to the motors, then the demand from the throttle to the motors creates a draw from the generator, which has to create the electricity to turn the motors directly - this means the engine has to throttle up and down to enable the generator to supply the current to meet the demand (e.g., when towing uphill or clearing a difficult off-road obstacle). Then you lose optimum fuel efficiency in the engine because it will either operate below or above its most efficient range to power the generator, as well as having to have more complex emissions controls, throttle controllers, etc, all of which increase the size of the engine package and complexity of the control mechanisms.

You sacrifice convenience (being able to drive as long as you like and refill any time) for efficiency (simpler motor designed to be optimized, leading to better durability, lower fuel consumption, and lower emissions).

Directly from the experts:

I think “hybrid” style batteries on diesel electric locomotives is a relatively new thing. Traditionally they just connect the alternator (generator) to the electric motors that drive the wheels. From UP’s website:

“Although commonly called "diesels," the locomotives actually are electrically driven. The diesel engine drives an alternator, which produces electricity to run electric motors mounted on the locomotive's axles.”

Also, extra weight in the locomotive is actually a good thing as it increases traction, allowing it to pull heavier trains.

 

[merrelljohnson]

The generator won’t do anything to add performance. That’s all the electric motors. The generator just adds charge to the battery and it doesn’t matter if the battery is at 100% charge or 10% the electric motors will perform the same.

The generator is just going to slow down the rate the battery loses charge to extend the range. It’s not turning a drivetrain so it only needs the torque needed to turn an alternator.

VW have 1.0 liter 3 cylinder engines, but the Harvester might be even smaller, maybe even something from Ducati. It needs to sit below the rear cargo area without taking too much cargo space away, as shown in the reveal video.

I think it’s going to sit behind the drunk.

 

[OIBScout]

It’s all fascinating, and clearly, there are some clever engineering people here.

At the end of the day, if our suspicions and the realities of current technology proof out, Scout Harvester won’t be classifiable as an EV. PHEV perhaps.

The important factors for many will be electric torque / performance, and range, especially for those who have never owned BEVs before.

Can’t wait to see what they come up with, even if I pivot to the BEV version, which should be capable greater than 350 mile range by the time production vehicles start rolling.

 

[oldgeeksguide]

I think it’s going to sit behind the drunk.

Ok, that raises a whole other set of questions

 

[Gottesacker]

I think the engine below the trunk is a good idea, but it would honestly be way cooler if they just put it in the frunk area and had a slightly bigger engine than just a three cylinder, and that way, the extra space below the trunk could be used for a bigger gas tank, which could extend the range even further.

Part of the appeal of these for me currently is that it still has a frunk. Take that away and I might as well just keep going with an ICE.

 

[Gottesacker]

Of course it will.

All the replies to me thinking I'm stupid and do not know what REEV is. But go check out i3 yourselves. If you have an underpowered engine that cannot even recharge your battery enough as you needed, the max power the battery out out would be equal (ideally) or less than what gas generator can put out. There's a reason RAM gives ramcharger the Penta v6. And it's why it's full battery performance is way higher, but when running on extender it's only the max power of the gas engine.

That would definitely be the most disappointing thing if the engine couldn’t keep up and you basically just end up with a “limp” mode like the i3.

 

[Chaparral]

That would definitely be the most disappointing thing if the engine couldn’t keep up and you basically just end up with a “limp” mode like the i3.

Scout have not set any expectations that the vehicle will keep going forever on gas. It gets 500 miles. Then you’ll probably be looking to charge.

It’s primarily an EV, Sout’s concept artwork shows a small generator that can only possibly serve to extend the life of the battery. It can’t be compared to vehicles with full sized engines and small batteries.

Most people will rarely need to use the Harvester. Most of the time is it dead weight that has a cost to move around. Making the generator small and lightweight is sensible from the point of view of efficiency. But when you need 500 miles it’s got your back.

The i3 generator was useless because it kicked in way too late. They made it that way to qualify for some government credits or something.

If the battery is low, charging a parked vehicle to 80% with the Harvester, if possible, and if it is a small generator like Scout’s concept artwork shows, will probably take several hours. So if there’s more driving to do, we’ll be recharging at an EV charger. But if we’re sitting around for a few days at a campsite and if we’re able to run the generator with the vehicle parked, it could be mostly charged by the time we leave.

Limping around at slow speeds could be dangerous. It would probably be better to charge with the Harvester while parked, then drive safely to the nearest charger at normal speed. I think charging while parked is a more essential feature than a limp mode.

But we’ll have to wait a see.

 

[Gottesacker]

Scout have not set any expectations that the vehicle will keep going forever on gas. It gets 500 miles. Then you’ll probably be looking to charge.

It’s primarily an EV, Sout’s concept artwork shows a small generator that can only possibly serve to extend the life of the battery. It can’t be compared to vehicles with full sized engines and small batteries.

Most people will rarely need to use the Harvester. Most of the time is it dead weight that has a cost to move around. Making the generator small and lightweight is sensible from the point of view of efficiency. But when you need 500 miles it’s got your back.

The i3 generator was useless because it kicked in way too late. They made it that way to qualify for some government credits or something.

If the battery is low, charging a parked vehicle to 80% with the Harvester, if possible, and if it is a small generator like Scout’s concept artwork shows, will probably take several hours. So if there’s more driving to do, we’ll be recharging at an EV charger. But if we’re sitting around for a few days at a campsite and if we’re able to run the generator with the vehicle parked, it could be mostly charged by the time we leave.

Limping around at slow speeds could be dangerous. It would probably be better to charge with the Harvester while parked, then drive safely to the nearest charger at normal speed. I think charging while parked is a more essential feature than a limp mode.

But we’ll have to wait a see.

Realistically I realize it likely wouldn’t be as easy as just refueling the gas tank and continuing on, but that wasn’t really what I was saying. I was merely saying that when the battery does deplete enough that the RE activates that I hope it can still perform at maximum capability until it runs out of fuel, but you touched on that as well in your last paragraph about limping around.

If it could literally be as easy as refueling that would be pretty dang awesome, but yea I don’t have my eyes set on that being a likelihood.