The efficiency the motor/generator in generating electricity is probably around 90%, i.e. 90% of the mechanical energy provided to the motor/generator is converted to electrical energy. The efficiency of the motor/generator in providing mechanical power is about 80%, i.e. 80% of the electrical energy provided to the motor/generator is converted to mechanical energy. This means about 90%*80% = 72% of the mechanical power provided by the ICE to charge the HVB is actually recovered in EV mode.
From my previous post, I mentioned that perhaps only 72% of the energy provided by the ICE to charge the HVB is actually recovered during EV operation. That is a big loss in efficiency. However, it is not really as bad as it may seem. The electric motor uses significantly less power to propel the car than the ICE.
For my 65 mph commute, the ICE needs to provide about 17.6 kW of power just to propel the car. The electric motor is consuming 6.9 kW of this power to generate electricity and recycling that electricity back to the generator which then supplies 4.9 kW power that sums with the 17.6 kW from the ICE via the planetary gear system. So 6.9 - 4.9 = 2 kW of power produced by the ICE is being used to control the planetary gear system. The ICE has to produce at least 2 kW more power than the motor. Actually, it has to produce more power than that to overcome additional transmission losses (1.4 kW of additional power).
The motor requires 14.2 kW of power to maintain the same 65 mph speed on the freeway. That is 14.2 / 17.6 = 81% of the power required from the ICE. So even though only about 72% of the energy supplied by the ICE to charge the HVB is recovered in EV mode, EV mode requires significantly less power. Effectively, we are recovering 72%/81% = 89% of the energy provided by the ICE to charge the HVB. That is a lot better than 72%. Having the ICE charge the HVB is not quite a free lunch (100% efficiency), but 89% is not all that bad.
Note that the power drawn from the HVB to power the motor at 65 mph is 17.0 kW, which includes 0.3 kW of power to run the car's accessories, i.e. fans, radio, lights, etc. The motor is thus 14.2 / (17.0 - 0.3) = 85% efficient at 65 mph.
Edited by larryh, 19 July 2014 - 09:19 PM.