JackFlorey said:
Nope. With direct drive, you only have one generator/motor - the bike's hub motor.
No, I mean ICE generator / ICE traction motor
Either design requires both a electric motor and ICE, so that point was a wash
JackFlorey said:
There are very few pure series hybrids. The Prius line are all parallel. The Volt claimed to be a series hybrid for years, then finally admitted they were series-parallel. This is due to efficiency considerations. From Green Car Reports:
"Today, the thing that has driven most automakers to series-parallel hybrids rather than pure series hybrids is a common scenario in U.S. driving: high-speed freeway driving. In such environments, multiple engineering teams over multiple decades have concluded that a mechanical connection to the engine offers better efficiency."
Only with inefficient traction ICEs coupled with early (underpowered) EV powertrains at the high power (density) required for freeway driving.
JackFlorey said:
The only pure serial hybrid I know of in regular production is the BMW i3 series, which actually has a completely separate motor/generator. (They call it a 'range extender'.)
Also the Nissan e-POWER platform as subject of this thread, Mazda rotary RE, etc.
JackFlorey said:
Nope. Regen charging converts to electrical energy, not mechanical energy.
No, I mean regen converts mechanical energy to electrical energy, same as an ICE generator, so this point would likewise be a wash, except that a generator is
far more efficient than traction ICE > regen.
JackFlorey said:
Again, it's all in the number of conversion steps, because each step costs you energy. Hence the parallel hybrid approach for efficiency.
Conversion steps are certainly important, but again, it's not
all in the number of conversion steps. A modern small gas generator is easily twice as efficient (g/kWh) as a bike kit motor, and the ICE itself is the overwhelming determinant of overall efficiency.
JackFlorey said:
Gas engine -> wheel is way more efficient than gas engine -> generator -> charge controller -> battery -> motor controller -> motor -> wheel. The only time you will use the ebike system is when you want to go faster or climb a hill (then you will add more power) or when you want to charge your battery (via regen.) Other than that, you use the power as-is.
This isn't accurate, as you're missing all the intermediate mechanical conversion steps between gas engine > wheel. As above, you're also missing that all those same generator steps apply for regen -- except again, charging via traction ICE > regen is a fraction of the efficiency of a gas generator. I get why you're not including it though, as below..
But I don't fundamentally disagree with you, because we're assuming different use cases. If you're using a traction ICE with mechanical linkage, it's a motorized bicycle (restricted) and it doesn't make sense to bring an EV powertrain at all -- just size the traction ICE appropriately. Which is the same argument against non-plug-in parallel hybrids -- they're not attractive on their merits in any way, and only become competitive with external incentives (tax breaks, HO vehicle lane access, wokeness, etc).
But this thread stipulates an EV powertrain. If you're already paying that penalty, you might as well make the most of it with a gas generator.
The future is series-hybrid with Atkinson cycle generators and then FPLGs.