What can we tell about Ford's EREV plans from... Ford's EREV?

[Newton]

Interestingly enough, Ford recently announced a new EV - the Ford Bronco New Energy. It is unfortunately only available in China and is in reality made by Jiangling Motors in China so it might never make it here in the US. Jiangling already makes EREVs in China and the Bronco New Energy is available in EREV or BEV form.

The Bronco comes with either a 105 kWh BEV with a 404 range, or a 43.7 kWh + 1.5l turbo gas with a 758 mile range. I had the trim breakdowns but can't find them any more - by memory the EREV is about $4K less than the equivalent trim BEV. The car starts at $32K EREV/low spec to $40K BEV/high spec.

We learned one thing about EREVs - or at least this implementation which is the big question about what happens when you run out of battery.

Zhou’s time with the Bronco EREV did include some off-road bits. Zhou was a little less positive on that front, partially because his time started with the battery at a low state of charge. This meant the Bronco’s engine was constantly on, trying to keep the battery topped up and the vehicle moving. Thus, the Bronco EREV's output is limited to however fast it can sustain the car’s demand for electric power. And a 150-horsepower engine just can’t give all that much power to the car’s 415-horsepower twin electric motor setup.

I have to give the journalist just a bit of grief here - the motor is not trying to "top up" the battery, it is responding to the demand of the 415 hp motors. At this output the battery is not getting any energy at all. Additionally, Generators are rated in kWh, not horsepower! Horsepower is the product of RPM and Torque, and generators do not care at all about RPM. The designer of a generator will chose some RPM on the engine that generates the desired torque to produce the rating of the alternator. This will be far less than the RPM of the rated horsepower of the (gas) engine. The fuel system will provide the right amount of fuel to keep the generator turning at that RPM as the torque requirements of the alternator vary with load. If you don't know the rating of the alternator, you know nothing about the generator. End rant.

So apparently the strategy here is that the EREV provides a form of 'turtle' or 'limp' mode where you get the additional 300 miles but with derated performance and probably little to no recharging. This is why it is critical to know the actual kWh rating of the generator, not the horsepower of the engine that drives the generator. I do not know if they will consider this acceptable for the new Lightning, because to me it means that you are still going to have to go to the scary fast charger if you want to have the performance that you expect.

Zhou also felt let down by the Bronco EREV's refinement when driving on regular roads. In EV mode the crossover is generally good, but in range extended mode, the noise, vibration and harshness is a lot more pronounced than other models.

“If you’ve been exposed to cars like the Li Auto range extended SUVs…I consider them world-class and unbeatable, but this [Bronco EREV] is a significant distance from that,” he said. Still, he remained positive. The Li Auto’s gas engine may be nearly imperceptible, but the Bronco EREV’s isn’t bad.

Again, it seems like you end up with two cars. This is quite dependent on the size of the generator chosen, but at this point Ford seems to see the EREV as something a little different than what I think we expect.

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[Lytning]

Out of everything in the Bronco New Energy article, this is what I find most interesting ...

"the Bronco New Energy is available in EREV or BEV form."

Now, THAT would seem to make the most sense for an @Ford Motor Company North American electrified truck line!

 

[chriserx]

Generators are rated in kWh, not horsepower

Kilowatts, an instantaneous output, not kilowatt-hours, a quantity of energy.

The designer of a generator will chose some RPM on the engine that generates the desired torque to produce the rating of the alternator

This is actually the base definition of horsepower, the production of work (torque) over time (the minutes in RPM). It can be expressed as either kilowatts or horsepower, though typically in modern times, horsepower is never used in electrical output. Although correlated, do not confuse the thermal output of the engine (typical engine horsepower) with the alternator's power output (kilowatt/horsepower).

 

[jsamp17]

1 Horsepower = 746 watts

So with my lightning I happen to have a 175.6 (usable) horse-hours pack, but I usually only keep 158 on hand. I also have a 1/4 HP TV.

I like the units game.

 

[ZeusDriver]

Generators are rated in kWh, not horsepower! Horsepower is the product of RPM and Torque, and generators do not care at all about RPM. The designer of a generator will chose some RPM on the engine that generates the desired torque to produce the rating of the alternator.

This is so stunningly wrong. 1. Generators are rated in kW, not kWh. 2. Generators do, in fact, "care" about rpm, because without rpm you do not have "power." In a simple permanent magnet generator, voltage varies directly with rpm, and torque varies directly with current. The product of voltage and current is watts, a measure of power. In Europe, all car engines are rated in kW, instead of HP. (The units convert perfectly.) 3. A designer will first chose an engine that is of the correct HP rating for the generator. Knowing the generator's efficiency, (say 90%) then the designer would know that, to get 10000 watts out of the generator, the equivalent of 10000/.90 (11,111) watts would be required of the engine. 11,111 watts is 14.89 HP.

As the combination is refined (which does not happen too much in portable generators, virtually all of them being quite inefficient) then the generator is wound to match the motor's most efficient operating point (or rarely gearing is used to match a generator with an engine -- but this would not happen in the Ford). Ford will evaluate many different engine generator combinations, and will almost certainly have to design the electric machine to match the output characteristics of the engine they choose. The process is iterative.

Small portable generators that produce household AC current, are virtually always (in the US) driven by engines at 3600 rpm, so the the produced power is at 60 hz. This fact is one reason that inverter generators are popular: in an inverter generator, the inverter sets the frequency. The engine can slow down, when the load is light, and the inverter takes care of keeping the frequency correct. When the load is light, an inverter generator is very quiet.

The generator in the Ford will very likely be producing three phase variable frequency AC, which will be converted to DC in the truck. The engine will run at high speed and high torque when under heavy load, and lower speed and lower torque when the load is light. The efficiency will likely be somewhat lower when running at reduced load, but the NVH experience will be better... a trade off between passenger comfort and efficiency.

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