2017 TOYOTA MIRAI fuel cell

77
Fuel cell system2
MIRAI_OM_USA_OM62023U2. Fuel cell vehicle
Fuel cell vehicle characteristics ................... 78
Fuel cell vehicle precautions ....................... 82
Advice for driving fuel cell vehicles ............................. 94

782. Fuel cell vehicle
MIRAI_OM_USA_OM62023U
Fuel cell vehicle characteristics
This diagram is for illustrative purposes only and may differ from the
actual vehicle.
Fuel cell vehicles efficiently use electricity, which is generated
by a chemical reaction between hydrogen and oxygen in a fuel
cell stack, and electricity charged in a traction battery to drive
the electric motor (traction motor).
The fuel is H
2 (compressed hydrogen gas), so the exhaust is
only water and water vapor. As they do not release emissions
such as CO
2 (Carbon Dioxide) and NOx (Nitrogen Oxides), fuel
cell vehicles are environm entally friendly vehicles.
Fuel cell vehicle components
Fuel cell stack
Hydrogen tanks
Traction battery Tailpipe
Fuel cell converter
Electric motor (traction motor)

792. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62023U
The electric motor (traction motor) allows smooth, powerful takeoff
and acceleration. This vehicle drives similarly to a gasoline vehicle
without any special actions by the driver. ( →P. 158) As there are no
engine sounds and the vehicle is qu iet, operation noises unique to
fuel cell vehicle components may be heard. ( →P. 8 0 )
The system may behave differently on cold days. It is performing a
special cold-start process to im prove start-up performance. (→P. 175)
Operation noises (→ P. 80), purge process ( →P. 175), etc., differ from
usual. However, this is not a malfunction.
Compressed hydrogen gas fuel can be filled at hydrogen stations.
Opening the fuel door ( →P. 198)
Driving the vehicle
Fuel cell system
Fuel filling

802. Fuel cell vehicle
MIRAI_OM_USA_OM62023U
■Sounds unique to the fuel cell vehicle
Due to the design of your fuel cell vehicle, there are various relays, valves
and pumps which under normal driving conditions will produce sounds. This
is a normal characteristic of the vehicle and does not indicate a malfunction.
Furthermore, way of hearing may differ based on usage environment or con-
dition.
Noticeable soundsSource of the sounds
Clunking, clicking and clack-
ingOperation of relays and hydrogen tank
valves
Sounds may come from under the floor or
behind the rear seats.
(Sounds may be heard when starting the
fuel cell system.)
KnockingThe parking lock is engaged
Sounds may come from the motor
compartment.
(Sounds may be heard when press the P
position switch or stopping the fuel cell
system.)
Whooshing, squealingGas is flowing through the nozzle and
valvesSounds may come from behind the rear
seats, or from the dispenser hose/nozzle.
(Sounds may be heard when filling the
fuel.)
• High pitch sound
• Gurgle sound
• Pulsing soundOperation of the pumpsSounds may come from the motor com-
partment or under the front seats.
(In particular, sounds may be heard when
starting the fuel cell system, accelerating
from a stop, or press the H
2O switch. The
sound may be louder when in Br mode or
when the vehicle decelerates during
dynamic radar cruise control.)
Humming soundOperation of the pumps are speeding up
Sounds may come from the motor com-
partment or under the front seats.
(In particular, sounds may be heard when
accelerating or decelerating.)
Whooshing sound Operation of the hydrogen injectorSounds may come from under the front
seats or behind the rear seats.
(In particular, sounds may be heard when
starting the fuel cell system, driving at low
speeds, or charging the traction battery.)

812. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62023U■
Regenerative braking
In the following situations, the vehicle generates electricity from the decelera-
tion of the vehicle while driving.
●The accelerator pedal is released while driving with the shift position in D.
● The brake pedal is depressed while driving with the shift position in D.
■ Charging the traction battery
Because electricity generated by the fuel cell stack and regenerative braking
charges the traction battery, the battery does not need to be charged from an
outside source. However, if the vehicle is left parked for a long time, the trac-
tion battery will slowly discharge. For this reason, be sure to drive the vehicle
at least once every few months for at least 30 minutes or 10 miles (16 km).
If the traction battery becomes fully discharged and you are unable to start
the fuel cell system, contact your Toyota dealer.
■ Charging the 12-volt battery
→P. 403
■ Parking
Because there is no engine sound or vibration, it is easy to mistake the fuel
cell vehicle for being off when it is actually still running, as indicated by the
“READY” indicator being illuminated. For safety, make sure to always shift the
shift position to P and apply the parking brake when parked.
■ Maintenance, repair, recycling, and disposal
Contact your Toyota dealer regarding maintenance, repair, recycling, and dis-
posal. Do not dispose of the vehicle or any of its components yourself.
• Humming sound
• High pitch soundOperation of the motor
Sounds may come from the motor com-
partment.
(In particular, sounds may be heard when
accelerating or decelerating.)
Blowing and draining soundExhaust water or air is being purgedSounds may come from the rear of the
vehicle.
May also occur periodically while parked
when it is cold to prevent freezing.
(Sounds may be heard when vehicle is
stopped, fuel cell system is stopped, park-
ing.)
Noticeable soundsSource of the sounds

822. Fuel cell vehicle
MIRAI_OM_USA_OM62023U
Fuel cell vehicle precautions
The fuel cell vehicle has hydrogen tanks (10150 psi [70 MPa,
714 kgf/cm2, 700 bar]), fuel cell stack, and hydrogen pipelines as
hydrogen-related components. Pay attention to all warning labels
attached to the vehicle.
This diagram is for illust rative purposes only and may differ from the
actual vehicle.
Hydrogen-related components
Warning label
Hydrogen detectors
Fuel cell stack Hydrogen tanks
Hydrogen tank valves
Hydrogen pipelines

832. Fuel cell vehicle
2
Fuel cell system
MIRAI_OM_USA_OM62023U
The fuel cell vehicle has high-voltage components (about 650 V maxi-
mum) such as a fuel cell stack, traction battery, power control unit,
high-voltage cables (which are distinguished from low-voltage cables
by their orange covers), electric motor (traction motor), etc., and high-
temperature parts such as the radiator for cooling. Pay attention to all
warning labels attached to the vehicle.
This diagram is for illust rative purposes only and may differ from the
actual vehicle.
High-voltage and high-temperature components
Warning label
Power control unit
High-voltage cables (orange)
Fuel cell stack
Traction battery
Service plug
Fuel cell converter Electric motor (traction motor)
Air conditioning compressor
Radiator for inverter cooling
Radiator for fuel cell stack
cooling
Auxiliary inverter
Cabin coolant heater

842. Fuel cell vehicle
MIRAI_OM_USA_OM62023U
When a certain level of impact from an accident is detected, the fuel
cell system is shut down and the system shuts out the high voltage.
Also, the fuel supply is stopped from the hydrogen tank valves. If the
emergency shut off system activates, your vehicle will not restart. To
restart the fuel cell system, contact your Toyota dealer.
A message is automatically displa yed when a malfunction occurs in
the fuel cell system or an im proper operation is attempted.
If a warning message is shown on
the multi-information display, read
the message and follow the
instructions. ( →P. 376)
Fuel cell vehicles do not have engi ne sounds like gasoline vehicles.
Therefore, it makes an artificial no ise at low speeds to notify pedestri-
ans and nearby vehicles that it is approaching. The sound varies with
speed and will stop when the v ehicle exceeds approximately 15 mph
(25 km/h).
Emergency shut off system
Fuel cell warning message
Vehicle proximity notification system