Truck & Off-Highway Engineering - April 2021 - 22

HIGH-VOLTAGE HYBRIDS
Cost of Ownership at 8 Years[$]
(24000 miles per year assumption)

250000
200000
150000
100000
50000
0

Base Price [$]
O&M cost [$]
Lost Payload Opportunity Cost [$]

Total Additional Cost [$]
Fuel Cost [$]

186555

167857

179838

5,071

1,611

62,570

67,080

83,438

27,495
1,671

43,870
5,044

26,400
0

70,000

P3 48V

P3 PY2

Baseline

Figure 9. Cost of ownership at eight years for P3 48V and full
hybrid compared to baseline diesel vehicle.

Energy losses from different sources [kWh]
Engine Losses [kWh]

Battery Losses [kWh]

Total Emotor Losses [kWh]

Total Driveline Losses [kWh]

Brake Losses [kWh]

Vehicle Losses [kWh]

Total Energy Losses [kWh]

16
14
12
10
8

14.76
12.18
2.10
0.98
0.99
0.20

6
4

11.38
2.12
1.11
0.85
0.14

7.85

7.132

P3 48V

P3 PY2

Figure 8.
Energy loss
comparison
between P3
48V mild and
full hybrid.

2.04
1.70
1.40
0.00

9.62

2
0

Baseline

Figure 7 compares the load shift on the engine operating map for
the ARB transient cycle for two optimum P3 configurations: 48V and
full hybrid with a two-year payback period. For the 48V P3 hybrid
configuration with limited electric-motor power capability, the hybrid
controller is able to eliminate the engine operation at low to medium
speed (700-1,500 rpm) and low loads (under 100 Nm).
When applying a 350V P3 hybrid configuration, the 30-kW electric
motor is able to replace a larger area of the engine operation on the
ARB Transient cycle, thereby resulting in a higher fuel consumption benefit and a CO2 emission reduction. Referring again to Figure 5, as the
payback period criteria is relaxed, the battery voltage increases and allows the application of higher-power electric motors. The larger electric
motor allows for a further replacement of the engine operating point
resulting in an increase in fuel-consumption benefit.
A further comparison of the 48V and full-hybrid P3 configurations in
terms of energy losses is highlighted in Figure 8. The P3 full hybrid shows
considerably lower engine losses due to the shift in engine operating pro22 April 2021

30
25
20

On Road CO2 Reduction relative to Baseline [%]
(Grams of CO2/Ton-mile Basis)
GT Real World Drive Cycle
ARB Transient

15
10
5
0

P3 48V

P3 PY2

Freight Ton Efficiency Improvement relative to Baseline [%]
(Ton-mile/gallon DGE Basis)

40
35
30
25
20
15
10
5
0

GT Real World Drive Cycle
ARB Transient

P3 48V

P3 PY2

Figure 10. CO2 reduction and freight-ton efficiency improvement
for P3 architectures compared on the ARB Transient and realworld drive cycles.
file as highlighted in Figure 7. The energy losses in the
hybrid component and transmission are comparable between both configurations. Overall, for the P3 configuration, the full hybrid shows 0.8 kWh lower energy losses
when compared to the 48V mild hybrid solution.
Figure 9 compares the cost of ownership between
the two P3 configurations against the baseline diesel
vehicle. The 48V P3 mild hybrid configuration shows
the lowest cost of ownership at the 8-year mark. The
48V mild hybrid benefits from the lower operating and
maintenance costs when compared to the full hybrid
application, while also performing significantly better
in terms of the fuel cost when compared to the baseTRUCK & OFF-HIGHWAY ENGINEERING

ALL IMAGES: FEV NORTH AMERICA

Figure 7. Load shift with P3 48V mild and full-hybrid configurations on the
baseline BSFC map.

Truck & Off-Highway Engineering - April 2021

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