EV with onboard generator

[JSH]

Originally Posted by Logic

IIRC the world average car trip is only 15 miles, so lugging around more batteries than that seems a waste.

California did a study recently on PHEVs using data collected directly from vehicle OBDII data to determine the reality vs the EPA test cycle for PHEVs. The test cycle assumes that 20 miles of range is needed to have 50% of vehicle miles traveled in electric mode. The vehicle data showed it was really a 56 mile range. As a result CARB increased the electric range to 50 miles for a PHEV to be considered a ZEV for Advanced Clean Car II rules

While the average individual trip is short the average car does multiple trips per day.

[Logic]

Obrist HyperHybrid – range-extended electric vehicle powertrain
Whats clever here is that Obrist can use a LOT of fuel saving piston offset as the 2 counter rotating engines exactly cancel out each others vibration.

MAHLE Range Extender Vehicle

ZF range extender system; production starts in 2026

[Logic]

Originally Posted by redpoint5

An EV with range extending ICE is probably not a good solution for most these days.

Plenty of hybrids get 50+ MPG nowadays, and that's extremely good.

EVs recharge quickly and infrastructure is mostly adequate these days.

Here's my comment on another forum-

On my recent 600 mile trip to Monte Rio I made the following stops, which worked out to exactly 1 hour spent charging.

10:30am Depart Silverton
2:00pm - Medford - 28min - 55 kWh (ate lunch)
5:00pm - Cottonwood - 15min - 35 kWh (bought groceries)
6:20pm - Williams - 17min - 39 kWh (stayed longer than the suggested 7min to arrive with a higher state of charge.
9:00pm - Arrive Monte Rio

Driving an EV set me back about 10min, and only because I decided to spend an extra 10min at my last stop to arrive with much more range. I was either getting food, using the restroom, or buying groceries at the other stops, and spent no time just sitting in the car. I averaged 130 kW and 400 miles per hour at the DCFC.

Considering series hybrid is the solution on trains, it follows that other very large machinery would most benefit from such a solution. I could see semis benefiting from a series hybrid system.

Asking AI, I got the following info-



I asked that because a fully loaded semi gets about 7 MPG cruising at 60MPH.

My back of the envelope figuring suggests we need a diesel engine capable of ~300 horsepower; enough to maintain speed, slowly charge the battery, and account for losses.

Based on Hummer EV specs, the semi motors should output 1,000 horsepower and requires a 205 kWh battery, which weighs 3,000lbs.

The upside is the ability to recapture energy during braking, hopefully massively reducing runaway truck incidents in the process.

The other upside is not needing to idle the truck to provide AC/electricity when drivers rest.

Edison Motors' 2nd prototype, a log hauling semi named Topsy uses a 250kw genset.

[redpoint5]

Originally Posted by Logic

Edison Motors' 2nd prototype, a log hauling semi named Topsy uses a 250kw genset.

335 HP is pretty close to my ~300 HP estimate. Dang I should have been an engineer.

[freebeard]

This has no more parts that a through the road hybrid but has the benefit of allowing AWD in EV mode.

What about the Wheel End Disconnect (WED)? An errant negation, or am I missing something?

An onboard generator does address one of my concerns, namely the hypothesized kill switches in all the AC transformers put there by foreign powers.

[JSH]

Originally Posted by redpoint5

I asked that because a fully loaded semi gets about 7 MPG cruising at 60MPH.

A loaded 2017 Freightliner Cascadia Aero X was doing real world 10 mpg at 65 mph. 11 mpg is the target today.

(On the test track the old 2014 Cascadia Evolution doing steady state loops managed 10.7 mpg but that drops to 9.3 in the real world economy test.)


For those that like YouTube: https://www.youtube.com/watch?app=de...uckyTruckSales

Originally Posted by freebeard

What about the Wheel End Disconnect (WED)? An errant negation, or am I missing something?

Those are simple clutches to disconnect the front axles when the front motor is not needed. No different than what AWD vehicles have been using for decades.

You would want the same thing in a through the road hybrid as you would not want to just put the FWD ICE in neutral when powering the vehicle in electric mode and have all the drag of spinning the axles and transmission. That would work for a shade tree mechanic hybrid but would reduce efficiency.

[Ecky]

There is a piece missing from this discussion so far.

Originally Posted by pete c

Each of these cars offer engines that make much more power than they need for cruising speeds.

What does such a car need? 40-50 hp, maybe for easy cruising.

How about going with a 2 cylinder of somewhere in the 600-800 cc range?

If we look at BSFC charts, what is the ideal engine size for cruising? Turns out, it's usually somewhere between 1.2 and 2.0 liters, depending on vehicle size, for an engine running at the peak BSFC point in its map.

Here's a BSFC chart for my car:



Peak BSFC occurs right at 2000rpm (+/-300), 75% load. At 2000rpm, with 60nm of torque (44ft-lbs), the engine is producing 16.7hp. The car needs approximately 16.7hp to cruise on flat, level ground. In 5th gear, at 2000rpm, the car cruises right around 60mph. This puts the existing engine size right at peak BSFC in top gear on level ground with the factory LRR tires and all underbody panels in place.

Go uphill very slightly, or remove some underbody panels on, or put tires on with higher rolling resistance, or forget to air up your tires and... the stock engine actually ends up being slightly too small for peak efficiency.

My car weighs 1800lbs. It has a 1.0 liter engine. For a 2700lb car, and assuming it has 1.5x the total drag (plausible), you'd expect the ideal engine size to be around 1.5L. And, indeed, most economy cars are in this weight class and have 1.5L engines.

~

Regarding why there aren't more range extended EVs, there are actually tons of them worldwide, they just aren't sold in America. For example, Nissan's entire hybrid lineup is exactly this, and they sell nearly every vehicle model they make with this hybrid variant (and often exclusively with it). The drivetrain is basically a Nissan Leaf drivetrain, but with a smaller battery, and there's a 1.5L engine spinning a generator as-needed, with no physical connection to the wheels.

As was already pointed out, this is actually not ideal, because it's lossy to convert from mechanical energy to electrical, then back to mechanical. The only reason to do this is simplicity - it can entirely eliminate the transmission from a car. Nissan's CTV transmissions are notoriously bad, so this is probably for the best.

Honda's solution is actually very similar to Nissan's, but it generally eliminates the downside of conversion losses by adding a single speed reduction gear and a clutch from the engine, allowing the engine to drive the wheels effectively 1:1 within a certain narrow speed range, which happens to be typical cruising speed on most highways. Otherwise it operates as an EV with a generator. Nearly every Honda model has this standard now in overseas markets. Even in the US, the Accord is only sold with this drivetrain now. The 1.5L (or in some cases 2.0L) engine happens to be at peak BSFC when cruising under these conditions.

So, the ideal engine size is just about the same as the engine size we find in cars today.

[Logic]

Constant rpm is important to keep in mind when thinking efficiency/economy.

Cheap! We like cheap.
A std cam, carburetor and ignition is easily tuned to be optimal.

Efficient:

The diagram is based on a sample of 1995 model year, naturally aspirated, EFI 2-valve engines.
The best BSFC is the red area centred around 2000 rpm and three-quarters load.
Each dot shows the speed and load for a typical mid size car at 1 second intervals during the US fuel economy test.
Of the time the car takes to do the test, just 5 seconds are in the island of best BSFC.
Quite a few of the dots (the authors say that they overlay) are at worst BSFC – idling at zero load with the car stationary!


Thx Julian Edgar - Autospeed

NB that this is based "on a sample of 1995 model year, naturally aspirated, EFI 2-valve engines"

If "just 5 seconds are in the island of best BSFC";
why bother to tune the the intake and and exhaust lengths etc. vs cheap and light.
So there's more to be had here.
Basically free economy. We like FREE! even better!

For tuned intake alone, no exhaust tuning:

11% better BSFC for tuned intake alone.

A 39% power and 23.5% torque increase. With pretty Bell Mouth pics!

[Ecky]

Truly highly efficient engines will need to be high compression and Atkinson cycle. They probably need to be direct injection. You can probably approach mid 30's thermal efficiency with a carb'd engine tuned for single-RPM operation, though this will only be at sea level and will vary based on humidity and temperature. Toyota's best are low 40's now, and the Chinese are claiming mid 40's.

[redpoint5]

Atkinson isn't so useful for constant output engines, as the Ramcharger demonstrates.