Harvester Directly Powering Motors?

[Logan]

But you could take gold and convert it to old currency and then buy stock in IBM, or the equivalent in 1955. Then when they start making the Scouts you can buy 3-

Biff.

Is that you?

(Side note, as a young kid, I was definitely confused on what exactly an almanac was due to Back to the Future. First time I saw a farmers almanac I was like "SWEET, we're RICH!". Took me a hot minute to realize what my 6yr old brain had thought it learned from that movie, wasn't exactly 100% correct ).

 

[Ike]

You only have to worry about the time issue if you go above 88 mph. For most driving, you'll be fine.

That should clearly be a setting in the truck to avoid accidental time travel. Otherwise I am not buying one.

 

[Logan]

That should clearly be a setting in the truck to avoid accidental time travel. Otherwise I am not buying one.

Does that theoretical setting just prevent you from hitting 88mph? Or does it disable the time circuits?

The first one seems easier, but the second one seems like a better implementation.

Or maybe they're just assuming the battery pack can't produce the 1.21 gigawatts, and that we won't be buying any plutonium, so its a non-issue?

 

[SpaceEVDriver]

That should clearly be a setting in the truck to avoid accidental time travel. Otherwise I am not buying one.

If anyone who isn't at Scout can guarantee anything about the new Scouts, it's that going over 88 mph will not send you back in time.

 

[CarTechGeek]

Totally disagree. Physical packaging & location of the Harvester is entirely part of the equation and absolutely must be a consideration for this discussion. Alluding to technology that exists today (in a full sized engine compartment) and not accounting for the fact that the Scout is not a car, but a truck, and that the Scout will have a FULL FRUNK are clearly at odds with each other. There must be some innovation around this implementation.

What you seem to be implying is that Harvester will have a relatively smaller generator, compared to vehicle size, vs other series designs. This is possible, and maybe even a good chance of that (which is a concern).

But that still doesn't change the pros/cons (all cons) of a "charging only" setup.

Limiting the generator to just charging, is a non starter even if you have a somewhat undersized generator, and in fact it's even worse then.

With an undersized generator it's even more critical that it can send power directly to the EV motor, where it could be supplemented by extra power from the battery if needed. If the generator can only charge batteries, then this necessary power combining mode would not be possible.

There are simply zero benefits and multiple obvious drawbacks, to limiting the generator to "only charging".

 

[J Alynn]

I think if Rivian can do a night rider update at Halloween SM definitely needs to claim that. And remember that once you hit 88 and go into the future-
SCOUTS ALWAYS COME BACK

 

[R1TVT]

The secret to EV trucks is clearly out de' bag

 

[Bodie]

Again, I have no dog in this fight, as I am only interested in the Pure EV with 350 miles of range!

And yet, sooooo much barking

 

[R1TVT]

And yet, sooooo much barking

If not having any definitive answers to share is barking, then I apologize.

For the record, reserving the pure EV does not preclude anyone from wanting to better understand how the Harvester will be implemented, or to see Scout succeed. I actually find the whole discussion to be fascinating, because of what we have heard and seen so far, but also because Scout could have just come out and said, "Hey, we're launching a Hybrid and an EV". But that didn't happen, and I think questions and debate are healthy here.

 

[TreeKiller]

I, for one, like this discussion. It is exciting to imagine what may become reality in the future, and it will be fun to come back to this thread in a year or two to see how right or wrong we were.

 

[CarTechGeek]

By far the most important detail will be how much power the Generator can produce...

 

[Moates442]

You are correct, it make sense to bypass the battery and go directly to the motors whenever possible.

That presentation by Scout was in "marketing speak". IOW dumbing it down for the masses.

I 100% guarantee that in many situations, Generator power will flow directly to Inverter (which is shorthand for inverter and all other power control electronics), from the inverter, directly to the wheel motors, bypassing the battery.

Everything is will be precisely controlled by the inverter. All the power has to go through the inverter to be conditioned, AC->DC and DC->AC conversion are done, and Voltage/current/Frequency is appropriately set.

The generator will be outputting AC, the motors run AC, the Batteries are DC.

Even if you could charge a battery simultaneously while remove more power from it than you are putting in (which you can't), you have to consider the waste of extra steps that charging first would require:

A: Generator (AC)->Inverter (convert to DC) > Battery (Charging DC) ...
... Battery (Discharging DC) > Inverter (convert to AC + adjust AC frequency) > Motor (AC).

Is MUCH less efficient than.

B: Generator (AC)->Inverter (adjust AC frequency) > Motor (AC).

No one in their right mind is doing A: when B: is possibly because B: is much more efficient.

A: doesn't even make sense except as separate steps. At any moment in time you can only charge or (exclusive or) discharge a battery. You can't do both at the same time.

100% guarantee that in many situations, Generator power will flow directly to Inverter (which is shorthand for inverter and all other power control electronics), from the inverter, directly to the wheel motors, bypassing the battery.

Can it work that way? I thought the job of the inverter was to convert High Voltage Direct Current to High Voltage Alternating Current. And the point of the generator would be to charge the High Voltage Battery and low volage battery (12 volt) through the battery regulation monitor or the DC/DC converter.

 

[CarTechGeek]

Can it work that way?

Yes.

Look back at post #9 in this thread, for explanations from a lead Nissan engineer.

 

[KarlT]

Is it possible that Scout, either accidentally or intentionally, is mistaken about the Harvestor having a frunk. Will they determine that it’s just not possible to hide a large enough motor elsewhere?

 

[J Alynn]

Is it possible that Scout, either accidentally or intentionally, is mistaken about the Harvestor having a frunk. Will they determine that it’s just not possible to hide a large enough motor elsewhere?

Nope! It fits. It’s a small nuclear reactor if you scroll back through to @LastDayScout ‘s post he describes how he saw it at the reveal. Admittedly I saw a glow coming from under the car after it got dark at the reveal but assumed it was just effect lighting for a WOW factor.

 

[Mousehunter]

I do not own an automotive EV, but have used various other electric vehicles. The "drive trains" start with a DC motor, then essentially creates a variable frequency ac signal to drive the motor. Resistance based speed controls in pure DC setups is less efficient - and I assume there are also issues with using pulse width modulation (pure DC), to control engine speed. Without varying the speed of the engine (which would cause the engine to run at a sub-optimal speed) - you will need to convert it's AC output to DC and then back to the AC at the frequency the motors need.

So yes, there will be inefficiency doing the inversion - but I don't think there will be much extra battery wear. The battery will be charging when the generator is creating excess current, it will be discharging when the generator is not - but I am willing to bet much of the generator charge current will be going to the motors and not effecting the batteries state of charge while on the highway. There is little need (other than designing it specifically for towing) to put an oversized generator in the Harvester package.

Putting in an oversized generator would be a trade off. It would be less efficient for daily driving. Now I can understand why Dodge did it with the RAM - as they want to sell a EV truck that can tow extended distances. That IS its selling point. But the cost of that oversized engine will be apparent in the sticker price and every time the truck goes to a gas station.

 

[CarTechGeek]

Putting in an oversized generator would be a trade off. It would be less efficient for daily driving. Now I can understand why Dodge did it with the RAM - as they want to sell a EV truck that can tow extended distances. That IS its selling point. But the cost of that oversized engine will be apparent in the sticker price and every time the truck goes to a gas station.

I don't consider the Ramcharger generator oversized. It's about right sized for a truck of it's size, if you want to consider towing in it's use case at all. Actually it's probably a bit undersized to cover all towing conditions, but the upside is that it will have no trouble meeting all power needs when not towing.

If you merely have enough power to just cover highway speed in ideal conditions, then you have a situation like the BMW i3 Rex: Where it can't maintain highways speeds on long uphill grades. Then IMO, it's undersized.

IMO you need to have a decent amount of extra buffer, to handle enough of the stress cases, so it doesn't become annoying to use, and that's before we even consider towing.

The tradeoffs for Ram using a bigger engine are minimal. The main impacts are weight and packaging. Loss of the frunk is probably the biggest impact. Batteries are so heavy that even with a V6 it will likely still be lighter weight than the pure EV, and the weight savings delta of using a smaller engine will be a negligible percentage of overall truck mass, so again negligible impact on efficiency.

Scout is making a different Tradeoff to preserve it's unique packaging, and is risking having an undersized generator to do it.

Scout is lucky the Ramcharger is a Stellantis product, and not a Toyota. Because all else being equal, I think more people would prefer to have a slightly oversized, than undersized generator in their EREV Truck.