acdii Report post Posted January 17, 2014 The biggest difference I see between the two is Gen1 can cruise neutral, no charge/discharge on the HVB, but the Gen2 is Very Very difficult to get into that stage, I have achieved it on occasion and saw 50+ on the instant, but any little bump, anything that could get you to move a fraction on the pedal and it was gone. The other note on this is you just can't maintain a steady speed doing this, you will slow down. (unless going downhill, and then you speed up like crazy). What this tells me is the ICE is putting out a lot more torque to the MG1 so it is always putting out power for either the traction motor or to the HVB or both. If you notice on the Gen1, the battery levels remain constant at anything over 45 MPH, which on mine was at 50% SOC on the dash. The only time this was not true was when it was in a conditioning mode, then it fully charged the HVB and the ICE ran 100% of the time. This new one doesn't do that, it charges similar to the Toyota HSD where it almost always went to full when above 42 MPH. When I go down certain roads that are horrible for any EV, I usually wind up with a full SOC, instant hovers around 40(higher in summer), and there is always a charge symbol on the battery. According to the PDF linked above, at this point the ICE should be spinning MG1, with MG2 providing the power to the wheels. Looking at the gauges provided, it does appear to be doing just that. SOC does not change, yet the ICE is always charging. When accelerating, or higher demand like climbing a grade, then ICE and MG2 are combined to propel the car. That is how I see it working. 1 hybridbear reacted to this Quote Share this post Link to post Share on other sites
larryh Report post Posted January 18, 2014 (edited) Above are the Atkinson Engine Map and the Motor/Generator Map for a Prius. To maintain constant speed, the car needs to maintain constant power. It can do so by varying the torque and engine speed along any line of constant power. As an example using the Atkinson Engine, if 15 kW are needed, then the car could operate at about 4000 rpm and 35 Nm of torque, consuming about 290 g/kWh of fuel. It could also operate at about 2000 rpm and 90 Nm of torque using 220 g/kWh of fuel. Both operating points provide the same power (maintain the same speed), but the later uses far less fuel, only 220/290 = 76% as much as the first operating point. So you would want to design the car to operate at the second operating point when 15 kW of power is required. You can think of engine torque and rpms analogous to the force applied to the pedals and cadence riding a bicycle. To maintain a constant speed on a bicycle, you can use a high gear, applying greater pressure to the pedals spinning at a slower speed; or you can use a low gear, applying less pressure spinning at a higher speed. Suppose instead of operating at 2000 rpm and 90 Nm of torque, we operate at 2200 rpm and 90 Nm of torque. Then, from the chart, instead of producing 15 kW of power, we produce about 16.5 kW of power. The fuel consumption for 15 kW is 15 kW * 220 g/kWh = 3300 g/h of fuel. The fuel consumption for 16.5 kW is 16.5 kW * 200 g/kWh = 3300 g/h of fuel. Thus is it possible for the engine to produce more power using the same or less fuel by choosing a more efficient operating point. The question is what to do with this excess power achieved by moving to a more efficient operating point. We can't just apply it to the wheels. That would make the car go faster. Instead, we could doing any of the following:1. Use the generator to charge the battery and place a greater load on the engine to absorb the excess power.2. If the generator produces more power than the battery can handle, we could divert some of the power from the battery to the electric motor. Going in series from the engine through the generator, then to the electric motor, and finally to the wheels is a less efficient route than having the engine directly power the wheels. That wastes some of the excess power that we need to get rid of, but allows the car to operate using less fuel. 3. If the battery is full, we could use energy stored in the battery by operating the generator in reverse and putting a load on the engine to absorb the excess power. This may seem wasteful at first, but it could place the engine at a more efficient operating point that uses less fuel. 4. It could be possible that the indirect route which requires more power from the engine (having the engine power the generator, which then powers the motor, and finally the wheels) actually allows the engine to operate at a more efficient operating point and use less fuel than using the direct route. I'm not an expert on engines. But this is what I think is happening based on what I have read. Edited January 18, 2014 by larryh 1 hybridbear reacted to this Quote Share this post Link to post Share on other sites
