Hybrid petrol engine for battery charge only: the best option?

Very inefficient compared to hybrid synergy drive.

My Volt does what you describe for low speed charge sustainment and a different mode with torque passing through once it's above 40 mph or so. The difference is night and day.

Yes, the cost of overnight charging should be added. How many kms did he get for each liter of petrol?

 

If you keep reading about the i3, you'll find that it has problems climbing long hills when the battery is depleted as the ICE can't supply enough power by itself. Also, many people on long trips will turn on the ICE while the battery still has lots of charge, run the gas tank to empty, then drive on the battery to the next gas station, as gas stations are more plentiful and faster to fill up at than a charging station.

 

Can one do that with a North American i3? I thought not.

 

Which is the ideal way of running a serial hybrid like the i3 on trips beyond its EV range. Turn the ICE on early(which can't be done in the US) on the highway or other stretch of road where the car will be cruising at a set speed. This saves grid charge for passing, hill climbing, and lower speed roads at the end of the trip. Volt owners, and likely other PHVs, do the same thing. This is actually how I pictured PHVs working when I first heard the concept. An ICE big enough to power the car about 60% to 80% of the time; to extend its effective range during a day of driving while saving grid energy for the beginning and ends of the trip. Not an ICE big enough to provide full power or infinite miles with a team of drivers.

To the OP, a serial hybrid has too much loss in energy conversion to be purely used on a non-plugin. The Accord hybrid comes the closest to it, but still directly connects the ICE to the wheels during higher speeds. For a plugin however, it could work. it will still be less efficiency in comparison to a parallel/serial hybrid like the Prius, but it may provide other benefits in exchange.

The Audi A1 E-tron had a rotorary range extender used in serial mode. Rotorary engines aren't known for their efficiency, but their power to weight ratios. This engine was tiny; 250cc, or about twice the displacement of a lawn mower engine, and it could power the car. The car had a 30 mile EV range, and only a 3 gallon tank, but that engine and generator sat between the rear wheels. Longer total range could have been possible, but Audi designed it to not give up interior space over the straight ICE model.

So a serial drive train can give more options in where it can be installed; it doesn't need a connection to the wheels. If the designers aren't going for infinite range, it can be smaller saving weight and space. The efficiency losses can be minimized by running the ICE at a limited set of rpms, but burning a little more gas isn't that big a deal. In a car within 75+ miles of EV range, lower fuel efficiency for the range extender will be more than made up by the greater ratio of EV miles.

 

if you have cheap electricity and high gasoline costs, anything is possible cost wise. but toyota builds the most efficient car in the world, dollar for dollar and pound for pound. i3 isn't even close, but it certainly has it's appeal and applications.

 

True, that option is not available in the US. The US version also has a smaller tank so that the gas range is less than the battery range, because if the gas range is longer it's no longer considered a BEV by the government (or at least CARB).

It's idiotic. Any interest I might have in a plug-in goes away when I realize that without the ability to manually turn the engine on, I'm likely to run out the battery and switch to the ICE right about when I get off the interstate and get into really heavy stop and go traffic (about 30 miles into a 40 mile commute). If they had chargers available at work I might be more interested.

 

It is because of CARB. They are being silly in assuming everyone buying a PHV will never plug it in, and/or it is to help promote FCVs. ZEV credits are too valuable for BMW to lose them on i3's sold with the range extender. So they worked out this BEx category with CARB that hamstrings ICE performance of the car in order to get the ZEV credits.

I won't be surprised when tuners start offering to unlock the full use of the ICE as in the European models. Still stuck with the smaller gas tank, but the larger one could be easily shipped from across the pond if desired.

 

Why waste fuel, weight, cost, and space on an engine for an occasional instance? Might as well get 4x4 SUV on the off chance you need to tow off road.

If the i3 ran as originally designed, and not hobbled by CARB, the issue it has with hills(or is actually mountains) here might never come to pass. In the US the ICE can't turn on until the battery is near discharged. In Europe, it can come on much sooner to keep portion of grid charge for such times.

 

Not exactly what I meant. Take away the km attributable to the battery tell me how far the petrol propelled it.

 

Partially.

I also own a Volt. For my purposes it's a much better fit.

 

The good thing about the planetary drives type of hybrids like Toyota's and volt's is that the torque needed to rotate the generator is transfered to the wheels. If the ICE was connected directly to the generator, this energy would be lost. This is why it's the best system for a PHEV, specially if it is more hybrid than EV. However, if the electrical motors where mounted directly into the wheels, eliminating the transmission and drive train, efficiency could be much better in both propelling the car and regenerative braking (I guess by about 20% based on the typical difference between crank and Wheel hp numbers). So the ideal setup for a PHEV would be something like a four Wheel drive car with two motor/wheels for the EV miles and a Prius Synergy drive at the other wheels for the hybrid mode. Maybe it is why there is Rumors of all Wheel drive for the next prius? Or am I just dreaming?

 

I can't say that I agree with your wheel motor assumptions.

Electrical generating, transmission (wire) and motor losses probably exceed what you're seeing in the drivetrain for something of this scale.
I can see it being done for secondary propulsion though (for the rear wheels of an all wheel drive for instance).