NissanTechNewsSummer2012:MarchStarTuned2005 9/14/12 5:22 PM Page 4
Nissan & Infiniti Tech News Feature
| New Growth: The Nissan LEAF
4 | Nissan & Infiniti Tech News NissanTechNewsSummer2012:MarchStarTuned2005 9/14/12 5:22 PM Page 5
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The LEAF was introduced in 2011 as Nissan’s pio- Nissan’s all-electric neer vehicle for the future of electric cars. It has a dis- tinctive body design not based on any other platform in LEAF incorporates the Nissan fleet, giving it a road presence unlike any other compact car. Prominent LED headlights and a long LED cluster tail light, coupled with blue-chrome both new and existing accents make the LEAF impossible to confuse with other vehicles. plus, once you pop the hood, nearly the technologies. only thing that looks normal is the faux “valve cover.” Let’s take a closer look at the features of the new This article will LEAF to try to strip away some of the mystery. familiarize readers with the unique features and design of this car, and provide insight into its expected maintenance
and service needs The stylish faux valve cover is set on top of the inverter unit and creates a traditional engine in the future. bay appearance.
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Nissan & Infiniti The NIssan LEAF
Overview The traction motor takes the place of a conventional The LEAF is a front wheel-drive car, utilizing an all- engine, and generates torque from precisely-controlled electric three-phase traction motor and reduction gear electromagnetic fields. The motor is basically two pri- to drive the CV axles. The motor gets its power from a mary components: the permanent magnet rotor, and the lithium-ion battery pack composed of 48 modules in coil windings of the stator. Information about tempera- series, each containing four ture or speed sensor loca- laminated cells to produce a tions, cooling tubes, and total of 403V. A water- high-voltage connections, cooled inverter changes bat- or other specific compo- tery power as necessary nents can be found in the from DC to AC to drive the service manual. motor, and, likewise, from When three-phase AC motor-generated AC (from current is applied to the regenerative braking) to DC stator coil windings, a con- to charge the battery pack. trolled electromagnetic Regenerative battery charg- field is generated. This ing is achieved by converting field pulls on the perma- the kinetic energy of the nent magnet inside the already moving car into rotor, causing the rotor to power through induction chase the generated field. within the traction motor. The Vehicle Control The suspension is independ- Module (VCM) can create ent MacPherson struts in the a constantly rotating elec- front, and a solid I-beam in tromagnetic field using a the rear with shocks. rotor position (angle) sen- Steering input is rack and sor, much as an internal pinion, with an electronically- The traction motor consists of the combustion engine regu- controlled electric power stator core (1), coil windings (2), output lates ignition and fuel steering rack. It’s equipped shaft (3), rotor core (4) and permanent using crank and cam sen- with standard ABS using magnet (5). sors. The torque generat- four-wheel disc brakes. ed by the electric motor is Vehicle Dynamic Control approximately proportion- (VDC) is standard, and enhances safety and handling. al to the amperage of the current, whose frequency (or The instrument panel has two separate displays for pulse timing) affects the rotational velocity. Current the driver, showcasing unique LED styling for electric application is controlled by the VCM monitoring posi- power consumption, and Nissan’s usual dot-matrix infor- tion with the traction motor resolver and current flow mation screen. An integrated navigation unit comes from a sensor within the inverter. standard, using GPS and telematics to show the vehi- Some DTCs (Diagnostic Trouble Codes) will limit the cle’s estimated range and nearby quick charge locations. rotor rotational speed, the torque output of the motor, or both as a precaution. A P3240 “Drive Motor Current Powertrain Control Malfunction” may set if the VCM does not see expected changes in current application due to sensor The first description of the LEAF is invariably that it’s error or an internal problem. The LEAF requires a CON- “an electric car,” so we should begin with how it works SULT-III plus for diagnosis and repair. without an internal combustion engine. Like an internal combustion engine that performs
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differently according to changes in the intake charge modes, when the battery is at the fully charged state, and timing, an electric motor is dependent upon the fre- no regeneration is performed. This is to protect the quency and amperage of the supplied current. It is the battery from overcharging. job of the VCM and the inverter to create the equivalent The heart of the powertrain is the 403V Li-Ion battery of an intake charge for the traction motor. It does this pack, arranged beneath the floor of the leaf. Every cell of by adjusting voltage based the 48 modules is moni- on two calculated values: tored, and the CONSULT-III target force, and motor plus can display many rele- torque request signal. vant PIDs for the battery Because the resistance pack, such as module volt- within the system is con- ages, total voltages, charg- stant, changes in voltage ing/discharging voltage dif- affect amperage propor- ferences, and the four bat- tionally – think Ohm’s Law. tery temperature sensor Target force is based signals. Yes, if there is a upon sensor input from the battery cell malfunction, a accelerator pedal position, DTC will point directly at the vehicle speed, and shift problem cell. Considering position. Other systems like the pack weighs a total 648 ABS or VDC will send lbs., we should be thankful torque-down signals to the that any one of the modules VCM to reduce motor can be replaced in the torque output. Once deter- event of failure. mined, the VCM will com- The LEAF comes stan- mand the inverter to con- dard with two ways of vert DC from the battery charging the battery pack pack into AC of the specif- at home using domestic ic amperage (torque) and AC. The “Normal Charge” frequency (rotational This diagram indicates the location of the method requires profes- speed). Thanks to thermo- 403V lithium-ion battery pack (1) and the sional installation of a dynamics, this conversion service plug (2). 240V source at home, and work also generates heat achieving a full charge will which is transferred into take approximately six the cooling system and dissipated by the radiator in a hours. The “Trickle Charge” method will allow 120V traditional manner. household electricity to fully charge the battery in The LEAF also charges the battery by working in approximately 21 hours. The trickle charge method is the reverse of the above method. Instead of creating not recommended for normal use according to the synchronous electromagnetic fields, during regenera- Owner’s Manual, but can be useful when at a friend’s tion the outer field is maintained stationary. The rotor house. This charging method may use power a bit magnet moves through the field creating a current erratically, charging and discharging capacitors for flow by the electrical property of induction. This AC example, that may trip household breakers or cause current is captured by the inverter, converted to DC, other leaks to ground. Anecdotally, it appears that the and stored in the battery pack. The VCM performs the trickle charge is not recommended due to its unrelia- regenerative charge constantly at deceleration, effec- bility. Using the trickle charge method will not cause tively slowing the vehicle. In ECO mode, the LEAF will damage to the vehicle. It is best to follow Nissan’s rec- regenerate more aggressively; however, in both ommendation.
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Nissan & Infiniti The NIssan LEAF
The port on the left is for quick charge. Shown here, the LEAF is using the shop’s 240V to get a little charge while in for service.
An optional “Quick Charge” port can be installed in the Transmission and Drivetrain LEAF, allowing a zero to 80% State of Charge (SOC) in about 30 minutes. These high-powered stations are The LEAF does not have a CVT or planetary gear available in some locations, and can be found using the transmission, but rather a reduction gear that looks much LEAF’s navigational unit. However, repeated Quick like the gears in a shop roll-up gate. The electric motor Charging may shorten the lifespan of the battery pack. output speed and torque can be precisely controlled so Every 12 months, regardless of mileage, Nissan there is no need for a conventional transmission’s chang- requires the annual Battery Usage Report for warranty ing gear ratios. On top of the reduction gear housing is purposes. This must be done with the CONSULT-III where the electronic park position actuator lives, and a plus. We will discuss the report below in the mainte- parking pawl is found inside the case. The LEAF uses a nance section. unique parking feature, which can be set or released with
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the electric shift selector, which power of the regeneration inputs the command (park, drive or process by monitoring the AC reverse) to the shift control module.. generated – simply the inverse Once set, the BCM transmits the of how it calculates target motor ON/OFF command to the electron- speed and torque. ic shift control module. The shift Here’s how the LEAF comes control module alerts the VCM of to a stop. First, the Stroke the signal, then commands the Sensor in the brake pedal parking actuator to operate, which assembly measures the pedal will lock or unlock the parking pawl travel (driver input) and gives appropriately. This is the electric this information to the IBU con- parking brake in the rear wheels, trol module. From this input, and not the parking gear in the reducer, with data from CAN communi- and has nothing to do with shift cations about the vehicle speed, selection. The LEAF cannot be available cooperative regenera- shifted while in OFF or ACC modes. tion slowing force, and wheel The LEAF utilizes standard CV speed sensors, the IBU module axles, so periodic inspection and commands the brake actuator to repair of the boots as necessary develop required hydraulic pres- will ensure long axle life. sure within the brake master cylinder using the actuator Brake and Steering motor to control the master Systems cylinder piston. As the traction motor develops braking energy The basics of the LEAF’s brakes through regeneration, the VCM are what you already know and will transmit the regenerative understand from most other vehi- force to the IBU using the CAN cles: disc brakes using hydraulic bus. The IBU will then command caliper pistons. However, Nissan the master cylinder actuator to introduces an electronically-driven reduce hydraulic pressure in Intelligent Brake Unit (IBU) that response to traction motor brak- integrates the brake control mod- ing. If the lithium-ion battery is ule with the master cylinder and an fully charged, no regeneration electronic brake booster. will occur and hydraulic pressure Because the VCM can switch alone is used for braking. the role of the traction motor into In the event of an emergency a generator when not accelerat- power outage, the LEAF can still ing, the LEAF must account for provide friction braking. The IBU this behavior in braking. When fail-safe feature allows physical you try to separate two magnets, master cylinder control with the it requires effort; the same force The RE1F61A reduction gear input brake pedal. When the LEAF has also occurs during the induction gear has 17 teeth, connected to a no power, solenoids that would process within the electric motor, 31-tooth main gear, which outputs otherwise be energized default to effectively slowing the vehicle through another 17-tooth gear to a position that allows the pedal to down. This is called regenerative the large, 74-tooth final drive gear. directly interface with the master braking, and it can be used coop- The final gear ratio is 7.937. In this cylinder. For this reason, it is nec- eratively with the friction brakes diagram, (A) indicates the power essary to power off the LEAF to stop the car. The VCM can input direction and (B) indicates during brake fluid flush mainte- measure the exact stopping the power output flow. nance in order to bleed the lines.
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Nissan & Infiniti The NIssan LEAF
The Intelligent Brake Unit is not independently serviceable, but is monitored completely by the VCM and will report any malfunction using the MIL and dedicated bulb indicators.
The LEAF’s Electronically Controlled Power Steering input, the greater the amount of current supplied to the System (EPS) generates optimal power assist torque EPS motor for assist. Since electricity is only required when based on the load on the front wheels, steering wheel turn- assist is needed, the total draw on the 12V battery is ing torque, and vehicle speed. The EPS unit is attached to reduced. The EPS employs a reduction gear to properly the steering column, and its output shaft connects to a transmit output torque into the rack assembly. standard rack and pinion. During operation, sensors detect Diagnosis and repair of braking and steering systems the motion and torque of the steering column (driver input) must be done with the CONSULT-III plus. After compo- and the EPS module calculates the necessary assistive nent replacement, it is often necessary to perform cer- power using an electric motor within the EPS unit. tain special service requirements. For example: a zero- Therefore, the motor can provide a varying amount of point calibration can be performed for the EPS so the assist based on steering input: the greater the steering return-home position is learned.
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Restraint System Nissan terms the “A/C Auto Amp.” The electric A/C and Miscellaneous Accessories compressor uses high voltage input to power a three- phase motor in an identical manner to that of the main traction motor. The driver can determine his or her The LEAF is equipped with many of the safety fea- desired level of cooling, and the A/C Auto Amp will elec- tures modern consumers have come to expect: driver, tronically control the A/C compressor speed to generate passenger, side, and curtain air bags. The the target output temperature. Because the compressor Supplemental Restraint Systems (SRS) are controlled can be controlled independently of motor speed, the in a conventional fashion, utilizing G-sensors, yaw sen- system is inherently more efficient than a belt-driven unit sors, and crash sensors to logically determine whether on a conventional car. As the compressor draws power a crash has occurred, from what direction, and with from the high-voltage battery, it will decrease the overall what severity. Repairing the LEAF after a collision range of the LEAF and should be taken into account requires more diligence than normal due to the pres- when discussing the Battery Usage Report. ECO mode ence of high voltage. Follow the service manual guide- will automatically decrease the power available to the lines for properly disabling 12V and high voltage prior A/C compressor. to working on SRS components. An “alternator” is simulated by using an onboard DC to Air conditioning is controlled electronically by what DC charger, which lives in the DC/DC junction box. The
Stroke sensor Input u Electrically- Required braking v Regenerative braking driven VCM force operation force operation intelligent w brake v Hydraulic braking Regenerative braking Traction motor force operation force x y Master cylinder Hydraulic control pressure sensor 1 z Friction brake Hydraulic braking force This flow chart describes the (Caliper) logic behind the LEAF’s cooperative braking technology. Required braking force u Pedal input value v Required braking force w Regenerative braking force effective value Control signal flow x Target hydraulic braking force* Hydraulic pressure y Adjustment pressure F/B Braking force z Hydraulic pressure x Target hydraulic braking force =v Required braking force w Regenerative braking force effective value
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Nissan & Infiniti The NIssan LEAF
high-voltage battery pack will automatically supply power to charge the on-board 12V battery as necessary. When the vehicle is stored OFF for an extended time, the VCM will periodically charge the 12V battery for five minutes every few days. Nissan cautions LEAF owners not to leave the HV battery SOC above 80% when storing the vehicle as it can affect the longevity of the battery pack. High-voltage components generate heat. Except for the battery, this heat is handled using an aluminum core radiator and electric fans. Two electric water pumps are controlled by the VCM and set in series to operate together for redundancy. The VCM can control the amount of cooling by directly operating the water pump duty cycle. Sensors within the DC/DC junction box, traction motor, and on the inverter will report operating temperatures to the VCM. Use only Nissan genuine pre-mixed coolant (blue), and never use stop-leak additives because they can damage the elec- trical components.
Maintenance and Driver Conveniences
The LEAF is equipped with cellular telemetry, live updates, and remote control. This system is called CARWINGS. The telematics control unit (TCU) lives under the dash, near the right passenger kick panel. Communicate with the LEAF remotely using Nissan cautions service personnel who rely on cardiac SMS on a cell phone, or the internet and a sup- pacemakers or other life-support systems to be mind- port device. Shown here is the Apple iPad app. ful of the interference that the telematics antenna can cause. The LEAF is capable of using both Simple A LEAF high-voltage Lithium-Ion battery that is nearly Message System (SMS; colloquially called text mes- discharged will begin to limit power distribution to the saging) and Internet connectivity to provide drivers traction motor and A/C systems to increase range. The with basic status information and bi-directional control charge limitation indicator (“turtle light”) will turn on to of some systems. Once owners have registered their alert the driver that the LEAF will no longer accelerate at username and password, they can use a supported the same rate. The Owner’s Manual warranty supple- device such as an iPad to check battery SOC, monitor ment will include emergency contacts for road-side and control at-home charging, or even begin cabin charging or towing. Towing a LEAF must be done with a conditioning using the HVAC. flat-bed, or with the rear wheels trailing. If a LEAF is Due to FCC controls and regulations, a unique VIN towed with the front wheels on the road, the traction and International Mobile Equipment Identifier (IMEI) motor may generate electricity and cause damage to the must be registered to any TCU. Therefore, it is not pos- EV components. sible to perform diagnosis or repair with a known-good The LEAF still requires periodic maintenance. TCU or a recycled part. Furthermore, a replacement TCU Nissan recommends changing the brake fluid and can only be activated using the CONSULT-III plus after cabin filter every 15K, along with inspections. The any replacement. The work support function provides high-voltage cooling system should be serviced every the necessary registration steps. CARWINGS will allow 125,000 miles. Details are in the LEAF service manu- users to locate nearby charging stations while traveling al. Every 12 months regardless of mileage, the EV without having to install GPS update DVDs. The naviga- component warranty requires a Battery Usage Report. tion computer is able to display the vehicle’s range, and This report is generated on a CONSULT-III plus, under display available stations. the maintenance function.
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Advice for your usage The recommendations below can help to minimize the ongoing impact on your LEAF Li-ion battery, which can affect your battery’s total capacity over its lifetime.
Cause of gradual Item 1 Recommendation 32Your score loss of capacity
Your score is very high Frequent use of and good for your Quick charging battery Charging Frequent charging Your score is very high when batter state of and good for your charge is already high battery
Too much electric Your score is very high and good for your Driving consumption This LEAF while driving battery driver is gentle Long term parking Your score is very high on the Storage with high state of and good for your high voltage charge battery battery.
The Battery Usage Report is a table designed to Recommendation Your score illustrate the projected condition of the battery under current usage. In the top graphic, the driver does not Use normal charge stress the high-voltage battery with repeated quick equipment charges, fast acceleration, frequent ACC-only “idling,” (not quick change) or continual use of the A/C. Gradual loss of capacity when possible is a normal battery characteristic. Nissan states that the HV battery is expected to perform at approxi- Select 80% charge limit mately 80% of its original performance after five years mode when your daily of average use. However, battery capacity and range driving journey is short can vary depending on a number of factors, including age and usage of the battery, number of passengers Use the ECO MOCE for a and payload, air conditioning/heater usage, high gradual and smoother speed or stop-and-go driving, and topography. acceleration and for a reduced drive load Springtime for Electric Vehicles
If your vehicle will not be The electric vehicle movement is gathering sup- driven for a long period of port and momentum, and will require an additional time, limit State of Charge level of expertise. Shops that train and familiarize to below 80% selecting 80% themselves with hybrid and electric vehicles will be charge limit mode able to retain their customers who eventually shift This LEAF driver may be a bit too aggressive in away from their conventional gasoline vehicles. The driving or usage habits. The Battery Usage Report can Nissan LEAF is very popular, and will show up in your help your customers improve their range. shop. Will you be prepared? |
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