Honda Fit Hybrid teardown (Part 1): Battery components & brake system

Electro servo-brake system, battery pack and power control unit presented



Honda Fit Hybrid
Honda Fit Hybrid on display at Honda Welcome Plaza Aoyama by Honda headquarters
* Click on the photo for a larger image.

 Disassembly of the Honda Fit Hybrid was performed on the 7th and 8th of November 2013 at the maintenance shop of the Saitama Institute of Automotive Technology (SIAT) in Ina, Kita Adachi Gun, Saitama Prefecture. The event was organized by the Saitama Industrial Development Corporation, Next Generation Automobile Industry. Later, on the 27th of November 2013, the disassembled parts were displayed for public viewing at the Saitama Industrial Technology Center in Kawaguchi City, Saitama Prefecture. A keynote speech was made on the same day on "development concepts and hybrid system technologies."

 The first day was spent for removing the drive battery, power control unit (PCU), and drive unit (engine and a 7-speed dual clutch transmission with a built-in motor). The removed components were further disassembled on the second day.

 Reported below (Part 1) is summary of the battery-related components and the electric servo brake system. The drive unit and the 7-speed dual clutch transmission with a built-in motor will be introduced under "Honda Fit Hybrid Teardown (Part2) " as soon as it is ready.

Related Reports: Toyota Aqua (Prius c) teardown: Part 1 (Nov. 2012)
Toyota Aqua (Prius c) teardown: Part 2 (Nov. 2012)
Nissan Leaf teardown (Part 1) (Mar. 2012)
Nissan Leaf teardown (Part 2) (Sep. 2012)
Nissan Leaf teardown (Part 3) (Nov. 2012)

Main specifications of the Honda Fit Hybrid

(click for more details)

Model name DAA-GP5
Body type 5-seater 5-door hatchback
Dimensions Length: 3,955 Width: 1,695 Height: 1,525 mm with 2,530mm wheelbase
Weight 1,080kg (1,140kg for S package, 1,130kg for the F and L package)
Fuel efficiency (JC08 test mode) 36.4km/liter (31.4km/liter for S package, 33.6km/liter for the F and L package)
System performance Max. output: 101kW/137ps, max. torque: 170Nm/17.3kgf-m

Note: Disassembled model is the F package.



Key component suppliers


Component Supplier
Drive unit 1.496-liter in-line 4-cylinder Atkinson cycle gasoline engine  (max. output: 81kW/110ps, max. torque: 134Nm/13.7kgf-m),  model name: LEB Honda (in-house)
Starter motor Mitsuba
Flywheel (clutch damper) Luk (Schaeffler)
Cylinder head cover MAHLE
Ignition coil Hitachi Automotive Systems
Throttle body Keihin
Intake manifold
VTEC hydraulic control valve
Engine management system (EMS)
Electric water pump (for cooling the engine) Aisin Seiki
Radiator fan Denso
Radiator hose Nichirin
EGR cooler Maruyasu Industries
Air-fuel ratio sensor Denso
Rear catalytic converter Yutaka Giken
Engine mount Nissin Kogyo
AC synchronous motor (permanent magnet synchronous type) with max. output: 22kW/29.5ps, max. torque: 160Nm/16.3kgf-m, model name: H1 Honda (in-house)
7-speed dual clutch transmission (DCT)
Dual clutch Luk (Schaeffler)
Electric gear actuator
Electrohydraulic clutch actuator Delphi Automotive
Transmission ECU Continental AG
Side cover ROKI
Battery Lithium-ion battery pack Blue Energy
Battery ECU Keihin
Contactor Panasonic
Battery wiring module Sumitomo Electric
Cooling fan motor Shinano Kenshi
Auxiliary battery Furukawa Electric
PCU Inverter Mitsubishi Electric
DC-DC converter TDK
Safety Disk brake Nissin Kogyo
Antiskid brake system (ESC)
ABS actuator
Electric servo brake system
Pedal feel simulator
Brake master cylinder
Servo (brushless) motor Mitsuba
Reduction gear, ball screw NTN
Brake hose Hitachi Metals (formerly Hitachi Cable)
Airbag ECU Tianjin Denso Electronics
Seatbelt Takata
Air conditioning Electric compressor Sanden
Interior, exterior Windshield Nippon Sheet Glass
Rear and side window glass Asahi Glass
Back door stay Showa
Rear-view mirror Murakami Corp.
Headlamp, rear combination lamp Stanley Electric
Side mirror lamp Koito
Seat TS Tech
Power window switch Alps Electric
Transmission lever
Other Electric power window JTEKT
Wire harness Yazaki, Sumitomo Electric
Fuel tank Yachiyo Industry



Before disassembly


Fit HV before disassembly Bottom view of the front floor
Fit HV before disassembly Bottom view of the front floor with Yachiyo Industry's black plastic fuel tank (rear center), exhaust pipe (left) and high-voltage cable (right).



Battery pack and power control unit (PCU)


Trunk before disassembly
Trunk before disassembly Trunk before disassembly
Trunk before disassembly with the rear seats folded forward. Lithium-ion battery pack and PCU are stowed under the silver cover. Honda refers to the battery pack and the PCU collectively as IPU (Intelligent Power Unit). Trunk before disassembly showing the rear right side behind the rear seat. The IPU cooling air is drawn in from the grid-like opening beside the seatbelt.


IPU cooling inlet duct Trunk after disassembly
IPU cooling inlet duct Trunk after disassembly
Inside of the trunk showing the rear right side behind the rear seat. The black duct (center) is the IPU cooling inlet duct. Trunk as seen from the rear seat after the IPU removal. Air goes out of the outlets (pointed by arrows) after cooling the IPU. The orange-colored high-voltage cable (center) connects the lithium-ion battery pack to the motor.


Intelligent Power Unit (IPU)
Intelligent Power Unit Intelligent Power Unit
The IPU (shown in the left-hand photo) is contained in a white translucent plastic case. The IPU weighs 42kg. It is shown removed from the case (in the right-hand photo, reversed from the left-hand photo) and measures 370mm in length, 650mm in width, 210mm in height. The red arrow points to the inverter. The DC-DC converter is behind the inverter. The blue arrow shows the lithium-ion battery pack. The green arrow shows the service plug. The purple arrow points to the junction board. The Toyota Aqua uses the nickel metal hydride battery pack stowed under the rear seat and the PCU (which integrates the inverter, DC-DC converter and the booster converter) over the transaxle in the engine compartment. The Honda Fit Hybrid uses the lithium-ion battery pack and the PCU (inverter and the DC-DC converter) side by side under the trunk. The battery pack and the PCU are separated from each other by foamed styrol. The yellow arrow points to the IPU cooling fan, and the white arrow to the outlet duct. Air taken from the inlet duct flows through the lithium-ion battery pack, the PCU, and the cooling fan before it goes out from the outlet duct.


IPU components

Junction board IPU cooling fan
Junction board IPU cooling fan
The junction board comprises the contactors for switching the electric circuits. It is fitted at the side of the lithium-ion battery pack and outside the IPU case. The white arrows point to the contactors supplied by Panasonic; the pre-charge contactor (left), main contactor (center) and sub contactor (right). The red arrow points to the main fuse, the blue arrow to the battery current sensor, and the yellow arrow to the pre-charge resistor. The IPU cooling fan uses Shinano Kenshi's fan motor. It measures 170mm in width (520mm including the duct) and 170mm in depth.


Battery ECU Lithium-ion battery cover
Battery ECU Lithium-ion battery cover
The battery ECU supplied by Keihin is fitted on the lithium-ion battery pack cover. It measures 170mm in length, 100mm in width, and 25mm in height. The underside of the lithium-ion battery cover. The cooling air intake port is shown at lower left.


Lithium-ion battery pack
Lithium-ion battery pack Lithium-ion battery pack
The lithium-ion battery pack supplied by Blue Energy is shown with the cover removed. The battery pack contains four modules, each module containing 12 cells, with 48 cells per pack. The pack weighs 42.5kg, occupies 60 liters in volume, and has 173V total voltage, 5.0Ah capacity and 0.86kWh total electric energy. The electric energy storage capacity of the lithium-ion battery in the new Fit Hybrid has been increased by 50% from the nickel metal hydride battery of the previous Fit HV. Battery module removed out of the IPU case (left). The arrow points to the temperature sensor. The IPU cooling air flows from the module top to the module bottom through the cells. Then, it flows to the bottom of the IPU case and to the PCU.


Battery module Battery cell
Battery module Battery cell
The module is shown standing on a side. The cells are connected in series. Each module weighs 4.5kg and has a rated voltage of 43.2V, rated capacity of 5.0Ah and electric energy capacity of 216Wh. Each cell weighs 277g and has voltage of approximately 3.5V.


Power Control Unit (PCU)
Power Control Unit Power Control Unit
The removed PCU is shown in the left-hand photo and its back side in the right-hand photo. The red arrow (left-hand photo) shows the inverter supplied by Mitsubishi Electric. The blue arrow (left-hand photo) shows the phase current sensor and the white arrow (right-hand photo) shows the DC-DC converter supplied by TDK. The PCU is cooled as the air coming from the lithium-ion battery flows between the inverter and the DC-DC converter. The air enters from the inlet port at the top of the DC-DC converter and goes out from the outlet at the bottom of the converter. Finally, the air travels through the IPU cooling fan and to the outlet duct.


Inverter DC-DC converter
Inverter DC-DC converter
The gate driver in the inverter. The inverter measures roughly 130mm in length,160mm in width, and 60mm in height as viewed from above. Inside of the DC-DC converter. It measures roughly 170mm in length, 170mm in width, and 55mm in height as viewed from above.



Electric servo brake system


Pedal feel simulator (pedal action) Tandem motor cylinder (brake action)
Pedal feel simulator Tandem motor cylinder
Pedal feel simulator supplied by Nissin Kogyo. The brake pedal is normally blocked off from the tandem motor cylinder. Since the amount of pedal stroke is sent to the electric servo brake ECU as signal, the driver will not feel a physical reaction from the pedal. To solve this problem, the simulator feeds the pedal stroking feel back to the driver. The silver part to the right (pointed by red arrow) contains the reduction gear and ball screw supplied by NTN. The dark part at the top (pointed by blue arrow) is the brushless servo motor supplied by Mitsuba. The silver part to the left (pointed by yellow arrow) is the piston supplied by Nissin Kogyo. Hydraulic pressure is generated in the cylinder and sent to four wheels. It measures 300mm in length and 150mm in width.
The electric servo brake system consists of the pedal feel simulator (pedal action component) and the tandem motor cylinder, stroke sensor and electric servo brake ECU (brake action components). The brake pedal movement is detected by the stroke sensor. The sensor signal is sent by the ECU to the motor of the tandem motor cylinder to regulate the ball screw and the piston movements. As a result, adequate hydraulic pressure is applied to the brakes. The addition of the servo motor contributes to precise control of hydraulic pressure and faster response. This, in turn, enables recovering the otherwise wasted regenerative braking torque at the onset and the end of braking. As a result, the recovery ratio has been increased by more than 60% from the previous Fit HV model. In an event of emergency braking or malfunction of the pedal stroke sensor, the hydraulic pressure in the pedal feel simulator bypasses to the tandem motor cylinder to activate the brakes directly.

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