Ran across this the other day.
https://insideevs.com/news/749596/ford-erev-suvs-super-duty-truck-2027/
What the heck is an EREV? Let's talk about it.
Given the current state of the art for vehicle batteries, you can built very reasonable cars and SUVs up the size of a light duty pickup truck.
But, what about those heavy duty cases? People tow big 5th wheel RVs and boats, sometimes going on trips for months at a time, putting in 450 miles a day to get from place to place. What about them? Can they electrify?
Yes. Mostly. Here's how.
The problem is that batteries are heavy and take a while to charge. As the amount of energy you need to store goes up, the weight goes up fast as does the time to recharge. So, while charging an SUV with a 100 KWhr battery from 10% to 80% might take only 20 minutes and get you 200 more miles of range, a heavy duty pickup with a 5th wheel might need a 300 KWhr battery, taking an hour to recharge and gaining only 150 miles in range. That would make for a long day with long recharging stops.
At some point in time, cheaper, lighter and faster charging batteries will be developed and solve this problem, but for now, the EREV seems to be the solution.
What is an EREV? An extended range EV where there is an engine-generator set on board. How is this different from a regular hybrid? Let's look.
Here are the various drive train configurations.
ICE: Gasoline engine drives a torque convertor that is connected to a transmission and then to the differential, rear axle and wheels. The transmission matches the engine output to the driving demand. Low gear for starting from stop. High gear for cruising at speed.
Hybrid: Same as ICE but add a motor/generator and battery which can capture braking energy and then reuse it to accelerate. A plug-in hybrid has a bigger motor and battery to allow the car to run short distances on electric only.
EV: A battery is connected to an electric motor that drives the differential directly.
EREV: The same as an EV but with a smaller engine generator set on board to recharge the battery while driving.
There are big advantages to the EREV over a hybrid. While a hybrid is basically an ICE car with small motor and battery added on, an EREV is basically and EV with an on-board gasoline powered charger.
The engine is big enough to run the vehicle at steady speed on the level, The battery would discharge to get up hills or accelerate, and recharge on downgrades and while stopping. An energy management system would maintain the battery at the right level for the day's trip and the route.
This has huge implications for the engine design.
A hybrid car needs an engine that has enough horsepower to accelerate from a stop and go up hills at speed. This means it has to be quite a bit larger than what's needed to cruise at steady speed on the level. It also needs a complicated, heavy transmission to match the engine speed and load to the conditions. Even under the best circumstances, the engine runs very inefficiently most of the time.
An EREV has a smaller engine/generator sized to provide steady-state cruising power, where the engine can run at steady speed and load and be optimized for efficiency. This should nearly double the efficiency. The engine emissions control should be simpler and less complicated, as well.
So, if you have an EREV HD pickup truck, you can get all the advantages of a EV in your day to day local driving, have good range for towing your 5th wheel or boat and have much lower fuel costs while doing it.
It's not as simple as having a straight EV, but is a good interim solution.
Here's some numbers for pickup trucks.
Note that the engine for the EREV is only 60 hp and one needed for towing a 5th wheel is 130 hp. If you were running the EREV-HD without the trailer, the engine would likely be managed to cycle on and off, about 50% of the time by an automatic energy management system.
Steady state driving on the level
The economics of EREVs look pretty good, even on a long trip where they are towing a 5th wheel trailer - more than $90 less than an ICE vehicle, even though only a small fraction of the miles is covered by the battery.
These steady state drives assume no regen braking. In actual conditions with hills, starts and stops, the economics would tilt a bit in favor of the EV and EREVs.
In urban/suburban driving, the huge advantage of EV over ICE vehicles remains due to regenerative braking and efficiency. (see https://blerfblog.blogspot.com/2024/11/)
Some notes:
In winter, the vehicles with engines can use the waste heat to heat the cabin, saving some energy and increasing range a bit.
The engine/generator set in the EREVs would basically sit where the "frunk" is now. A front electrical motor might have to be sacrificed to make room, as well.
Engine/gen set could be small 3 or 4 cylinder automotive engine or even a small gas turbine like this https://www.kitplanes.com/heron-turbine/
There is a clutch in the torque converter of hybrids to allow the motor to drive the car with engine turned off.
For ICE cars with manual transmissions, a clutch sits where the torque converter is shown.
Diagrams depict typical rear wheel drive arrangement. Many cars, typically with front wheel drive, combine the transmission and differential into a "transaxle".
EVs still typically use a single motor with differential for the rear drive and another in front, if AWD. Some day, individual motors built into each wheel will likely replace this arrangement.
