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Charging the battery while driving, only to then use that electricity to drive the wheels, is an inefficient use of petrol.
You're converting petrol->electricity->ChargeBattery->ExtractFromBattery->DriveMotor. Each stage has some energy loss involved. Ideally you'ld use the petrol to 100% drive the wheels and not recharge the battery at all, and arrange your use of electricity so that 100% gets used up by the end of the trip, and also so that as much driving in built-up areas is electrical, in order to minimise exhaust fumes breathed by pedestrians etc nearby.
 

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I would humbly dispute that.
when charging the battery the engine will be utilised on a more efficient mode than to power the wheels.
Nothing new that some hybrids will use the engine on its most efficient mode to charge the battery and use the motor for wheel power.
The gain in efficiency is larger than the electric losses in the process.
 

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I would humbly dispute that.
when charging the battery the engine will be utilised on a more efficient mode than to power the wheels.
Nothing new that some hybrids will use the engine on its most efficient mode to charge the battery and use the motor for wheel power.
The gain in efficiency is larger than the electric losses in the process.
I would be interested to see typical numbers that support 'the gain in efficiency is larger than the electric losses'
 

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Without going technical,
an engine is 20 to 25% efficient. (when powering wheels)
Are you saying that you will have 75% losses in heating and friction on an electric motor?
 

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Without going technical,
an engine is 20 to 25% efficient. (when powering wheels)
Are you saying that you will have 75% losses in heating and friction on an electric motor?
I'm not putting forward any numbers, I'm simply requesting a view of the typical efficiency numbers for the various electrical energy interchanges between the ICE and the electric motor output shaft, that support your statement...
 

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I'm not sure about the precise arrangement of drive system on the 330e. It may be true that running a petrol at it's most efficient speed to generate electricity might be a better option than running it at, say, very low speed crawling along in traffic. Certainly you can do this in Ampera because having an epicyclic gearbox with inputs from ICE and large electric motor, as well as another electric motor/genny where the flywheel would be, this car can play lots of clever tricks like running petrol at optimum constant speed feeding some power straight to wheels (max efficiency) as well as charging the battery with the excess mechanical power going to the small electric motor(in generator mode), and using the large electric motor to provide the variable-speed needed as car accelerates & slows down. Very clever stuff indeed.

However, I don't think the BMW is anything like as sophisticated, and I don't know if it's possible to decouple the ICE from the wheels in such a way as to charge battery optimally with ICE at constant speed, while also driving the car electrically along the road. If this is not the case, then the ICE speed is going to be coupled to wheel speed via 6/7/8-speed transmission, and it's going to be under varying load in all probability at the car goes up & down a bit. So it may be a lot harder/almost impossible to guarantee optimun charging.

On a seperate area of efficiency for OP's interest, one technique to maximise electrical efficiency is to avoid heating the car electrically. The technique is to heat the cabin really hot (25C or more even!) when running on petrol, so using the waste ICE heat. Then, turn the heating off, fans, a/c off etc, and switch to electrical driving for a few miles. The cabin will cool slowly, and when your toes start to go numb, go back to petrol & warm the car up again!

This isn't always appreciated by passengers in the car, unless done gently & subtly so they don't notice! With a bit of luck they fall asleep when the cabin's toasty warm! :)
 
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