U.S. Department of Energy report on 2010 Prius (Gen3)

usbseawolf2000 · Oct 28, 2010

Argonne National Laboratory (U.S. Department of Energy) released their first study of 2010 Prius (Gen3).

The MY2010 Toyota Prius represents the most recent iteration of Toyotaâ€™s hybrid system which began wide-scale production in 1997. As with the majority of Toyota hybrid systems, this version includes an Atkinson-cycle engine, two electric machines and a power-split device used to control the allocation of energy between the electric and mechanical (fuel) power paths. As with most hybrid systems, fuel economy and emission gains are enabled through regenerative braking, engine-off at idle, electric operation at low road loads, electric assist, and the general ability to operate the engine more optimally. In addition to the broad goal of generally improved fuel economy, the MY2010 Prius also specifically seeks to improve the vehicleâ€™s real-world fuel economy, namely, hot and cold weather operation as well as improving high-speed operation with minimal compromise to urban driving.

To accomplish these objectives, the majority of the Priusâ€™ hybrid components have been redesigned or updated. Engine displacement has increased to 1.8L versus the previous 1.4L in order to increase efficiency at higher vehicle speeds. In order to maintain low-speed vehicle efficiency, an Exhaust Gas Recirculation (EGR) system was included. Additional engine related improvements include an electric water pump and an exhaust heat recirculation system. The recirculation system allows for exhaust heat (loss) leaving the engine to be absorbed into the engine coolant when desired. The hybrid transmission and electric machines were also redesigned to facilitate an overall transmission length and mass reduction. More specifically, gearing was included between the motor/planetary gear set and compound gearing was also included. The motor/planetary gearing is to allow for reduced motor torque while still providing high power through increased motor speed (~ 13000 rpm maximum versus previous ~9000 rpm maximum speed). The compound gearing integrates several functions such as a parking gear and counter drive into a more compact package. In addition to these mechanical components, the power electronics and battery packaging have also been redesigned to facilitate mass and volume reductions. Overall, much attention has been paid towards reducing the mass and volume of the newly developed system while continuing to improve fuel economy.
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There are many graphs and charts. One of the most interesting is the cold weather penalty. Gen2 had 14% vs. Gen3 10% fuel economy penalty.

The gas engine also revs lower on the highway. This report confirms what Toyota told us. It is amazing that 2010 Prius stays around 1,250 RPM 42% of the time.

Their conclusion:

Preliminary testing has provided significant insight into the operating strategies and behavior of this new and state-of-the-art vehicle. The MY2010 Prius achieves high fuel economy and clearly works to improve operating regimes that are often problematic for hybrid vehicles. Relevant findings include:

Significant engine-off operation during Urban operation as well as some engineoff operation at higher speeds.

A reduced fuel economy penalty between warm and cold Urban operation.

Use of a specific fueling/operating strategy for initial catalyst warm-up during the cold Urban cycle.

Lower speed engine operation at higher vehicle speeds due to larger engine displacement.

De-rating of battery regeneration capability during US06 testing and repeated acceleration.

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Read the entire report: http://www.ipd.anl.gov/anlpubs/2010/06/67317.pdf

bwilson4web · Oct 29, 2010

I especially enjoyed this comment:

pp_23 said:

For this testing, 10 back-to-back maximum accelerations were run to assess performance fade, the degradation of performance over repeated runs. Hybrid vehicles typically scale back performance after a certain number of runs due to battery management issues relating to state-of-charge management or thermal management. Figure 32 shows the repeated performance cycles for the current generation Prius. It is quite interesting to see that performance stays nearly constant across all of the 10 runs. This consistent performance is due to minimal de-rating of positive battery power even after 10 performance runs. Also of interest, is that regenerative power during the deceleration back to zero mph begins to reduce after about the fourth cycle. This is similar to what was observed during the US06 cycle and suggests that the regenerative power is reduced before reducing the tractive power, minimizing the effect on acceleration performance.
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This is due to the accumulated heat from the exothermic NiMH charge:

By moderating the charge, two good things happen:

Pack does not thermally overheat and drive up the internal pressure.

Minimize latent gas generation during charge cycle to reduce excess internal pressure.

These are strategies that substantially improve the projected life of the traction battery.

Bob Wilson

usbseawolf2000 · Oct 29, 2010

Thanks for pointing that out. Gen3 is rock solid awesome.

U.S. Department of Energy report on 2010 Prius (Gen3)

usbseawolf2000 HSD PhD

Attached Files:

Gen2_Gen3_Prius_Cold_Penalty.png

Gen2_Gen3_Prius_Highway_Engine_RPM.png

bwilson4web BMW i3 and Model 3

usbseawolf2000 HSD PhD

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U.S. Department of Energy report on 2010 Prius (Gen3)

usbseawolf2000 HSD PhD

Attached Files:

Gen2_Gen3_Prius_Cold_Penalty.png

Gen2_Gen3_Prius_Highway_Engine_RPM.png

bwilson4web BMW i3 and Model 3

usbseawolf2000 HSD PhD