2014 Ninth International Conference on Ecological Vehicles and Renewable Energies (EVER)

Fuel Cell Triple Hybrid Drive Train for Motorcycle

Joerg Dieter Weigl
Engineering Design & InnovationCentre
Faculty of Engineering
National University of Singapore
Bock E1A, #03-03, 1 Engineering Drive 2
Singapore 117576
Email: joerg_weigl@web.de

Abstract - Motorcycles with electric drive are a Fuel Cell Electric

Power
clear advantage for cities, because of locally no System Conditioner Drive
emissions and driving with minimum noise pollution. (with
This is especially known in South-East-Asian cities 1 Diode) 4
with strong motorcycle traffic [1]. But pure battery
Battery Ultra
electric motorcycles have a significant range Capacitor
problem. This problem can be overcome with a
hydrogen fuel cell hybrid system. Motorcycles in city 2 3
driving have a very sharp load profile from extreme
acceleration and sudden deceleration. To cater for Fig. 1: Schemata of triple hybrid drive train.
this extreme load profile a triple hybrid systems with
fuel cell, ultra capacitor and battery, have been II. DESCRIPTION
developed and extensive tested. Tests of the triple The essence of the triple hybrid configuration is to
hybrid system show a comparable acceleration and utilize the advantages of different power systems. In the
top speed performance in comparison to an battery - example of World harmonized Motorcycle Test Cycle 1
fuel cell only hybrid design. Additionally in the triple or 2 (WMTC), the power to overcome the load is
hybrid the load cycle energy on the hybrid battery provided by three energy providers together. The fuel
can be reduced by 48% in exurban drive cycle test. cell provides the average power, the battery with its
An ultra capacitor – fuel cell hybrid only cannot large capacity provides the energy for load variations
provide the same performance as the triple hybrid or and the ultra-capacitor with its low internal resistant,
the battery – fuel cell hybrid. high efficiency and very fast response caters for the fast
load peaks from the system. With this configuration, the
Keywords — Electric vehicle, Fuel Cell Vehicle,
fuel cell system is subjected to less load variations. With
Motorcycle, Hybrid.
a more constant load profile, the fuel cell system can
significantly extend its lifetime and improve its
operation efficiency. As the sudden surge in load power
I. INTRODUCTION TRIPLE HYBRID DRIVE TRAIN demand is provided by ultra-capacitor with long cycle
Like illustrated in Figure 1; the triple hybrid contains life, the battery lifetime is also extended; charge and
of three possible electric energy providers for the electric discharge efficiency is also improved. In general, the
drive. The source of energy is hydrogen; fuel cell is the hybridization process improves the peak power
prime energy converter. Battery and ultra capacitor store performance and load response as well as overall
electric energy from fuel cell and regenerative braking and efficiency.
take peak load of fuel cell system. Ultra capacitors have
higher power density and high efficiency. Batteries have In comparison with the triple hybrid system which is
high energy density. Ultra-capacitors take fast load cycles used in a bus mentioned by Proton Motors [3], this
from battery to reduce stress on battery and improve system is simplified. There is only one power
electric storage efficiency. conditioning step in the motorcycle application instead
of three for three different energy sources. To minimize i. Triple hybrid with fuel cell, battery and ultra
the system effort and size, simplify the control strategy capacitor (FC-Bat-UC)
and shorten the response time no additional power ii. Fuel cell hybrid with battery (FC-Bat)
converter was implemented between ultra-capacitor and iii. Fuel cell hybrid with ultra capacitor (FC-UC)
motor / battery. The drive train for the motorcycle has
some similarities to the triple hybrid concept describe by The specifications of the main hybrid drive train
Keränen [2] for fuel cell forklift but the challenges in components are given in Table 1.
packaging size and weight are significant different for
motorcycle.
TABLE 1: SPECIFICATIONS OF HYBRID DRIVE TRAIN
COMPONENTS
III. EXPERIMENTS AND RESULTS PEM-Fuel cell system
Fuel Cell (FC)
A. Experimental set up Cooling water cooled
The experimental comparison of the triple hybrid Operation Temperature max. 75°C
drive train with other drive trains were done with a self-
developed hydrogen fuel cell motorcycle on a chassis Power & Voltage 7 kW @ 53 V
dynamometer as shown in Figure 2 Model `Hydrogenics` HyPM7

Weight 39kg

Battery (Bat) Lithium Polymer Battery /

Thunder power

Measured Capacity for 1C discharge 3.6 Ah

Discharge rating / Charge rating 20C / 5C

Number of cells 14cells

Voltage for pack (max – min) 58.8V -42V

Battery pack temperature during test 38-48℃

Weight 1.62kg

Specific energy density 160 Wh/kg (nominal)

Specific power density 3200 W/kg (nominal)

Ultra Capacitor (UC) Based on Maxwell

BPAK03500- 15EA
Fig. 2: Fuel cell motorcycle on chassis dynamometer for hybrid drive
train tests with data acquisition system. Capacity / Max Voltage 29 Farad / 60 V

Discharge and Charge rating >400A

A data acquisition system on the fuel cell motorcycle
Arrangement 4Series x 2Parallel
monitors all the energy flow inside the motorcycle
hybrid system as well as the energy input by hydrogen Internal Resistance 0.038Ω on DC
through the fuel cell system. The dynamometer captures Weight 4.622 kg
the mechanical energy output and performance. Both Specific energy density 10 Wh/kg
data acquisition systems are synchronized. The data
where computed with Microsoft Excel. Specific power density 5192W/kg

The setup allow to test different fuel cell hybrid

B. Performance Test
configuration, the following 3 configurations where
selected for the comparison as they demonstrate the The performance of the different hybrid
main possible hybrid configurations for a passive configurations where determined with acceleration tests.
controlled triple hybrid system: The tests were performed from stand still with wide open
throttle to full speed. Figure 3 gives plots of the
acceleration performance results.
 C. Efficiency Test
Efficiency test where performed with drive cycle tests.
The tests are based on the relationship of work done to
energy consumed. It was further determined how much
energy was provided directly by fuel cell and how much
energy was going through hybrid storage of battery and
ultra capacitor.

World harmonized Motorcycle Test Cycle (WMTC)

for urban driving (WMTC 1) and exurban driving
(WMTC 2) as in Figure 4, where e the selected drive
FC–Bat–UC FC-Bat FC-UC
Triple hybrid Fuel cell hybrid Fuel cell hybrid with
cycle. According to the maximum speed of the
fuel cell, battery and with battery ultra capacitor motorcycle; test were done according to reduced speed
ultra capacitor
mode.

Fig. 3: Acceleration performance comparison of triple hybrid with

battery–fuel cell and ultra capacitor–fuel cell hybrid.

The acceleration (slope of the speed curve) are for the

triple hybrid and battery hybrid nearly the same, for the
ultra capacitor hybrid the acceleration drop after the
constant acceleration phase significant compare to the
others. This can be explained by the ultra capacitor
power (UC Power) being exhausted after the constant
acceleration. Because of the rising powertrain voltage
the ultra capacitor is starting to recharge and is taking
additional power out of the system till stable speed is
reached. The top speed of the ultra capacitor hybrid
depends fully of the power output of the fuel cell system
(FC Power) and is therefore lower than for the other − for urban driving
hybrid systems. The battery and the triple hybrid system − reduced speed mode <60km/h
have a similar top speed thereby the battery only hybrid
reach a slightly higher top speed. This different in top
speed comes from the same effect described already at
the ultra capacitor only hybrid system; there the ultra
capacitor is start recharging before top speed is reached.
This effect could be avoided with a control which delays
the recharging of the ultra capacitor till top speed is
reached. This control will be included in future work.

The triple hybrid system shows in comparison with

the other hybrid systems a significant reduced fuel cell
power. This significant reduced fuel cell peak power is a
clear improvement for expected fuel cell lifetime and
with this reliability of the whole triple hybrid system.

A similar reduction on peak power can be observed − simulates intercity and rural road driving
for the battery in the triple hybrid system. Compare to − reduced speed mode <95km/h
the battery only hybrid system the charge cycle stress on
the battery is reduced and a longer lifetime can be Fig. 4: World harmonised Motorcycle Test Cycle WMTC for
expected for the triple hybrid battery. motorcycle; based on wide international data range with real world
 driving characteristic. Published by United Nations (2008-2010) in:
measurement procedure for two-wheeled motorcycles [4].
In Exurban drive cycle test (Table3) the tank to wheel
Table 2 and Table 3 give the efficiency results of the efficiency is generally higher and highest for the triple
drive cycle test. For urban driving in WMTC1 the fuel hybrid with 42.6%. This general trend is mainly due to
cell ultra capacitor hybrid (FC-UC) has a slightly higher the fact that the fuel cell is in a more efficient operation
tank to wheel efficacy with 33.9% compared to the triple area. The balance of plant of the fuel cell system with
hybrid with 31.0% this is mainly due to the higher the blower, pumps and fanes have a minimum power
storage efficiency of the ultra capacitor compare to consumption which is always needed than the system is
battery. Performance and reliability wise has the FC-UC in operation partly independent of the power output so if
hybrid difficulties to follow all acceleration and top the power output increase the percentage of this balance
speed demands. of plant losses compare to the output power decrease and
the system efficiency increase.
TABLE 2: EFFICIENCY RESULTS FROM DRIVE CYCLE
TEST IN WMTC1, URBAN DRIVING
D. Hybrid contribution analysia
WMTC1
Figure 5 illustrates the results of how much energy
FC-Bat FC-Bat-UC FC-UC
come direct from the fuel cell and how much energy is
Battery efficiency 96.2% 98.0% 0 passed through the hybrid storage of ultra capacitor or
UC efficiency 0 99.9% 99.8% battery during one drive cycle in WMTC 1 and 2.
Power conditioning
efficiency 95.9% 94.7% 95.0% Drive Hybridisation configuration
Diode efficiency 99.0% 99.0% 99.0%
cycle FC-Bat-UC FC-UC FC -Bat
Motor efficiency 73.9% 81.4% 80.5%
test Triple Hybrid: Fuel Cell Hybrid Fuel Cell Hybrid
Efficiency of regen 5.5% 3.7% 8.4%
Fuel Cell, Battery, with Ultra with Battery
Fuel cell stack efficiency 57.2% 54.2% 54.1%
Fuel cell system efficiency 49.0% 45.3% 45.3% Ultra Capacitor Capacitor
Tank to wheel efficiency 30.2% 31.0% 33.9%
WMTC
1
Petrol Equivalent L/100km 2.23 l 2.14 l 1.97 l
Wh/100km 20212.Wh 19432.Wh 17894.Wh

TABLE 3: EFFICIENCY RESULTS FROM DRIVE CYCLE

TEST IN WMTC2, EX-URBAN DRIVING
WMTC2
WMTC
FC-Bat FC-Bat-UC FC-UC
2
Battery efficiency 98.3% 93.2% 0
UC efficiency 99.9% 99.9% 99.9%
Power conditioning
efficiency 96.7% 96.5% 96.1%
Legend
Diode efficiency 99.0% 99.0% 99.0%
Ultra Capacitor energy contribution
Battery energy contribution
Motor efficiency 79.7% 81.6% 88.9% Fuel Cell direct energy
Efficiency of regenerative 68.9% 42.6% 6.6%
Fuel cell stack efficiency 58.9% 59.4% 56.2% Fig. 5: Pie chart comparison of the contribution of the hybrid
storage in two different drive cycles
Fuel cell system efficiency 53.3% 53.5% 50.3%
Tank to wheel efficiency 40.4% 42.6% 42.3% The result show that the triple hybrid has the highest
combined use of energy storage in battery and ultra
capacitor together, and therefore the lowest peak load
Petrol Equivalent L/100km 2.02 l 1.91 l 1.94 l
demand on the fuel cell system. This increases the
Wh/100km 18351.Wh 17324.Wh 17603.Wh
expected fuel cell system lifetime and therefore the
system reliability. At the same time the load cycle on the ACKNOWLEDGMENT
battery in the triple hybrid is compare to the battery only The author says thank you for contribution to Prof.
hybrid, is reduced by 48% which also has a significant Hamdani Saidi, Prof. Georg Brasseur, Prof Jürgen
effect on the expected life time of battery and with this Garche, Prof. Andreas Öchsner, Dr. Inayti, Joseph Koh,
on total system reliability. Habibu Uthman and Helia Mohammadi Sepahvand.
The energy provided direct by fuel cell is for the
battery only hybrid and ultra capacitor only hybrid the
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