Hybrid Electric

Vehicle

A Dolcera Report
December 2005
 Rationale

Automobiles are a source of considerable pollution at the global level, including

a significant fraction of the total greenhouse gas emissions.
• On July 22, 2002 California Governor Gray Davis signed into law AB 1493
(commonly known as the "Pavley law") — precedent-setting legislation to reduce
global warming pollution from motor vehicles.

• This bill directs the California Air Resources Board (CARB) to develop and adopt
regulations that achieve the maximum feasible and cost-effective reduction of
greenhouse gas emissions (GHG) from passenger cars and light trucks sold in
California. 
Source: http://www.ucsusa.org/clean_vehicles/vehicles_health/californias-global-warming-vehicle-law.html)
 Development I

The new millennium is bringing a millennial change to the

family car. A few years back, the key concerns were:
• Pollution,
• Nagging worries about global warming, and
• Oil shortages.
These concerns led to the development of Electric Vehicle
(EV’s) powered by batteries. But current battery
technology does not provide EV's with a range that is
acceptable to consumers.
Limitations of EV’s:
• An average commute to work is around 40 miles.
• EV's have a range of 80-100 miles using advanced battery
technology.
• While batteries need frequent recharging, they are not the only
way to power an electric car.
 Development II

HEV is just the first step in reducing the environmental

impacts of automobile use with out loosing-off comforts,
performance, storage room and extended driving range.

Advantages of HEV’s

• HEV contains parts of both gasoline and electric vehicles in an

attempt to get the best of both worlds.

• HEV is able to operate nearly twice as efficiently as traditional

internal combustion vehicles.

• Equivalent power, range, cost and safety of a conventional

vehicle while reducing fuel costs and harmful emissions.

• The battery is continuously recharged by a motor/generator

driven by the ICE or by regenerative braking.
 Components of HEV Battery system

The batteries in a HEV are the energy storage device for the electric
motor. Unlike the gasoline in the fuel tank, which can only power the
gasoline engine, the electric motor on a hybrid car can put energy into
the
batteries as well as draw energy from them.

• Battery:- Two or more electrochemical energy cells connected together to

provide electrical energy.

• Generator:- The generator is similar to an electric motor, but it acts only to

produce electrical power.

• Electric motor:- Advanced electronics allow it to act as a motor as well as

a generator. For example, when it needs to, it can draw energy from the
batteries to accelerate the car. But acting as a generator, it can slow the
car down and return energy to the batteries.

• SOC:- The State of Charge of a battery is its available capacity expressed

as a percentage of its rated capacity.
 HEV layout

Wheel Wheel
IC Engine IC Engine

Transmission Generator Battery Transmission Generator Battery

Motor Motor
Wheel Wheel

Scenario 2: Braking – Kinetic energy is Scenario 3: High speed – Power is

Scenario 1: Low speed - Power is converted to electric energy during
provided by electric motor using energy provided by IC engine and electric motor
regenerative braking by electric motor via generator. Generator also charge
supplied by the DC battery and supplied to battery. battery during high speed.

Wheel IC Engine

Transmission Generator Battery

Motor
Wheel
 HEV battery system design parameters
Factors affecting battery performance
• Temperature:- Battery performance is highly dependent on temperature.
each type of battery works best within a limited range of temperatures.
• Battery age/Shelf life:- Corrosion is the main component behind decreased
performance in lead acid type batteries by age.
• Depth of discharge:- Batteries are able to maintain their performance longer
when they are not deeply discharged regularly.

Design parameters:
• How much space is available for the batteries?
• How much can they weigh?
• What is the desired range?
• What is the weight of the vehicle?
• What is the targeted vehicle cost?
• How will the batteries be recharged and
• What kind of drive system requirements is needed?

These are necessary questions because of the variety of battery types

available and the differences between them. The chart below lists the
characteristics of the most common types of batteries.
Source: http://www.atti-info.org/technology/ev_tech.html
 Types of HEV’s batteries and performance
There are many types of batteries that are currently being used - or being developed for
use - in HEVs. The following table lists these types along with their common
characteristics. The types are listed in descending order of popularity for use in HEVs,
with the most popular choices at the top of the table. Source: http://www.atti-info.org/technology/ev_tech.html
Self
Energy Power Discharge Current Future
Cycle
Battery Type Density Density Rate Cost Cost Vehicles Used_In Other Notes
Life
[Wh/kg] [W/kg] [% per [$/kWh] {$/kWh]
month]
CARTA bus,
25 to 75 to 200 to 100 to
Lead-Acid 2 to 3 75 Solectria E10
35 130 400 125
(sealed)
Potential: 55
Audi Duo, GM
Advanced 35 to 240 to 500 to Wh/kg, 450
EV1 (VLRA),
Lead Acid 42 412 800 W/kg, and 2000
Solectria Force
cycle life
Toyota RAV4-EV,
Toyota Prius, Potential: 120
Nickel-Metal 50 to 150 to 600 to 525 to 115 to
Chrysler Epic Wh/kg, and
Hydride 80 250 1500 540 300
minivan, Honda 2200 cycle life
EV, Chevy S-10
Nickel- 35 to 50 to 1000 to 300 to Potential: 2200
10 to 20 110 WWU Viking 23
Cadmium 57 200 2000 600 cycle life
100 to 400 to Potential: 1000
Lithium-Ion 300 Nissan Altra EV
150 1200 Wh/kg
Zinc- 56 to
100 500 300
Bromide 70
Lithium 100 to 100 to 400 to
100
Polymer 155 315 600
NaNiCl 90 100 400
110 to 240 to
Zinc-Air 100 300 100
200 450
Vanadium
50 110 400 300
Redox
 Comparison of top 3 batteries used in HEV’s
Lead Acid Advanced Lead Acid Nickel-Metal Hydride
Low cost Longer cycle life than conventional lead acid. High cost
Low energy density Valve regulated lead/acid (VLRA) Higher energy density than lead acid not as
batteries are showing great promise. susceptible to heat
Longer recharging time (as 6 to 8 hours) Shorter recharging time

Only fair cycle life

Can be ruined by completely discharging

them.

During recharging it is important to maintain the balance of battery. The balance of battery is maintained by
controlling battery from
• Overcharging and
• Over discharging

Controlling is achieved by defining State of Charge of battery

• Upper limit value – overcharge and
• Lower limit value – over discharge

When overcharge is detected power generation is controlled/cut-off and when over discharge is detected
power supply to electric motor is stopped. Detection is achieved by appropriate sensors.
This report investigates various procedures available/adopted by various assignees in order to maintain
balanced battery pack by avoiding overcharge and/or over discharge.
 HEV battery system concerns

The ultimate goal of HEV can only be achieved with the balance battery pack.
Since the main source of energy in HEV is batteries and recharging is carried
out on-board.

Advantages of balance battery pack:

• Balancing of battery SOC’s increases battery life
• Automated balancing circuitry will decrease overcharging
(and gassing) and decrease manual maintenance.

This in turn provides

• Equivalent power range at low cost as conventional vehicle while
reducing fuel costs and harmful emissions.
• Can travels twice the distance of a conventional vehicle on the
same amount of energy.
 Objective

The present report attempts at finding out various aspects and

approached involved in maintaining balanced battery through patent
and non-patent information. Few patents have been selected to
identify:
• IP activity over years
• Competitors
• Competitor and Market Landscape
• Technology map – Based on patent technology focus
• Technology approach - Competitor’s
 IP activity over years

The activity graph displays patenting activity over years in the area of
overcharging of HEV battery. The problem seem to be quiet old, the
graph indicates first attempt was made in 1978 to solve the problem
Since then there has been continuous efforts with high and low activity
through out. The graph indicates thick IP activity during 1995-1997S.
4

3 3
3 3

2 2 2
2

1 1 1 1
No. of patents 1

0
0 0
0
1978 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003

Priority year
 Assignee wise IP activity
Companies with most HEV battery patents are arranged in decreasing
order in below graph. Top three players are Nissan motors with (5) patent
records to its credit, followed by Toyota with (4) and Acqueous (3).

5
5

4
4

3
3

No. of patents
2

1 1 1 1 1 1 1
1

0
MOTORS

MOTORS

ACQUEOUS

MOTORS

MOTORS

MOTORS
LOCKHEAD

HYBRICON
GENERAL
TOYOTA

ELECTRIC
NISSAN

SUZUKI
HONDA
MOTOR

SANYO
FORD
MARTIN

Assignees
 Competitor and Market Landscape
The below left graph display assignee wise IP activity over years, according to the present data the
very first patent pertaining to HEV battery charging system was filed by HYBRICON in 1978 but not in
the race anymore. Though NISSAN, AQUEOUS and TOYOTA seems be ahead in acquiring max.
number of patent to their credits, but not active since 2000. GM and HONDA have bagged a single-
single patent of same age in 2003.
The below right graph display market (countries) eyed by various competitors. The hot market place
for most competitors is Japan (17) followed by United States (11) and Germany (04). According to the
present data Nissan seems to be having strong presence in Japan market than rest with 5 patents
protected, followed by Aqueous and Toyota
We will look in to their technologies in competitor approaches section coming latter in the report.
 Distribution of patents based on technology focus

The above pie chart displaying various factors that has affect on battery charge and discharge and numbers
indicating the distribution of patents in that area from selected list of patents. The distribution of patents is
based
on technology focused in the patent.
• Power generation: Technologies disclosed in patents for modes of power generation in HEV for
charging battery and ways of handling
• Power management: Technologies disclosed in patents for managing the battery balance during
power generating and/or consuming
• Fluctuating HEV operating mode: Technologies disclosed in patents for managing battery balance
during fluctuating operating modes, especially in composite HEV
• Power supply: Technology disclosed in patent for starting engine with auxiliary battery current when
main battery current is not sufficient to start engine
 Technology map – Based on patent technology focus
Patent number/ Fluctuating hybrid Series/parallel
Power Generation Power management Power Supply Assignee
Priority year operating mode HEV
Operating the starter/
US6583599 (2003) - - - PHV
Alternator as a motor.

JP08098321 (2003) - - SPHV forcibly run as SHV - PHV

Motor driving stop or off -

US6504327 (2000) - - - SHV
Upper & lower limiting voltage
Comparing battery voltage
US5550445 (2000) - - - SHV
With predetermined value

US6809501 (2000) Idling in slow traffic - - - SHV

SHV mode or continuous-type PSHV mode is controlled by

US5722502 (1995) - - - PSHV
driver or based on the SOC of the accumulator.

US4351405 (1999) High speed - - - PHV

JP2001078306 (1997) Regenerative braking - - - PHV

JP06055941 (1997) Regenerative braking - - - SPHV AQUEOUS

JP10295045 (1997) Regenerative barking - - - SHV

JP06319205 (1996) Regenerative braking - - - SHV AQUEOUS

Restarted after an
JP2001268707 (1996) - - - SHV
idiling stop released
Regulating number of
JP10084636 (1995) - - - PHV
rotations of IC engine
Control unit stops
JP09200907 (1995) - - - PHV
generator output
Controlling generated power
JP11136808 (1994) - - - SHV
of a generator
Operates generator at number of revolution AQUEOUS
JP09117010 (1993) - - - PHV
corresponding to number of revolutions of IC engine
Maintaining charge capacity
US5828201 (1993) - - - SHV
of battery modules
Suppressing the engine
US20050038576 (1992) - - - SPHV
torque vibration
Automotive elec. system
US6392380 (1978) - - - SHV
battery is used to starts engine
 Clustering – Technology focus
Various methods of
Event Output Effect Action
Power management

Comparing battery voltage

With predetermined value

Regulating number of
rotations of IC engine

Control unit stops

generator output

High speed
Power generated/ Overcharge Controlling generated
Regenerative braking Power management power of a generator
consumed
Over discharge
Restarted after an
idiling stop released Operates generator at
number of revolution
corresponding to number
of revolutions of IC engine

Maintaining charge capacity

of battery modules

Suppressing the engine

torque vibration

Operating the starter/

Alternator as a motor.

Fluctuating hybrid Power generated/ Overcharge

Power management SPHV forcibly run as SHV
operating mode consumed
Over discharge

Motor driving stop or off -

SPHV – Series/Parallel Hybrid Vehicle
Upper & lower limiting voltage
SHV – Series Hybrid Vehicle
 Technology approach – Competitor’s
In technology approach patent and non-patent literature is used to extract information about the technology
profile of various assignees such as

• Years in this activity

• Type of batteries used
• Battery charging system
• Type of HEV (Series (SHV)/Parallel (PHV)/Composite (SPHVS))
• Technology strength based on citation analysis
• Product Vs patent identification
• Battery management solutions proposed (i.e. current control/cut-off system and SOC detection
technique)
• Scientific literature and technology news to strengthen the report, since patent activity is a slow
process.
 TOYOTA MOTORS - Technology approach
Battery type: Lead-Acid battery
Battery charging system:
The charge to a DC-battery is provided by the generating power from a generator and the regeneration power
from the drive motor at the time of braking.
Patent #/Priority date Current control/Cut-off system SOC detector

US5550445 (1993) During heavy load state, generator Voltage sensor and an SOC sensor detect a
output is controlled to be increased voltage and an SOC of the battery and feed the
and motor output is restricted. When detected results to the controller.
heavy load is not detected, generator
and motor output is stopped or avoided
Series/parallel composite thus preventing battery overcharging.
electric vehicle (SPHV)
JP08098321 (1994) When the charged state of a battery is The SOC sensor detects SOC of a cell and the
out of a first control target range, the voltage sensor detects the electrical potential
ECU makes the SPHV forcibly run as difference of a cell for the rotational frequency of
the SHV. With this constitution, even if a motor.
the PHV running is continued for a long
time, the charged state of the battery is
controlled with a certain frequency, so
that the overcharge or over discharge
of the battery can be avoided.
JP09200907 (1996) The generation-of-electrical-energy SOC is controlled within proper limits. If SOC falls
output of a generator is suspended by from a lower limit, a generator will be operated by
the time it reaches the electrical- the maximum output, and if SOC exceeds a
potential-difference upper limit limiting upper limit, a generator will be operated with the
value of the DC-battery. minimum output.
US5722502 (1995) Overcharging is prevented by using SOC sensor detects accumulator SOC and SOC
mechanical loss of engine, generator is maintained to the desired range by using forced
and the torque distributing system. mode control.
ECU shift to SHV mode during
discharging (i.e. Heavy load) is thus
preventing battery from discharge.
 TOYOTA MOTORS - Technology approach

Various Methods of
Event Output Effect Action
Power Management

Heavy load- generator o/p is

controlled to be increased and the
o/p of the motor is restricted.
No heavy load- The increase
US5550445 (1993) control of the generator output and
High speed the output limit of the motor are
stopped or avoided.

Overcharge/over discharge of the

JP08098321 (1994) battery is avoided by making
Fluctuating hybrid SPHV forcibly run as the SHV
operating mode (series hybrid vehicle) by an ECU
Power generated/ Overcharge (electronic control unit) when the
Power management
consumed charged state of a battery is out of
Over discharge a first control target range.
JP09200907 (1996)
Regenerative braking Overcharging is avoided by
suspending the power output of a
generator by control means, when
electrical-potential-difference value
of the DC-battery reaches upper
US5722502 (1995) limit.
Fluctuating hybrid
operating mode Overcharging is prevented by
using mechanical loss of engine,
generator and the torque
distributing system. ECU shift to
SHV mode during discharging (i.e.
Heavy load) thus preventing
battery from discharge.
 Findings

Product Patent

TOYOTA PRIUS US5722502

TOYOTA HIGHLANDER US6691809

 NISSAN MOTORS - Technology approach
Battery type:- Lead-acid and/or Nickel-Hydrogen battery
Battery charging system:-
The battery is charged from the power generated by the generator and regeneration power from a motor.
Electric motor functions as a generator to charge the battery when a hybrid vehicle is restarted after an idling
stop released.
Patent #/Priority date Current control/Cut-off system SOC detector Scientific Literature
JP10084636 (1996) Output of generator is restricted The DC-battery is equipped with (Non-patent info)
depending on the battery condition the DC-battery condition
Battery by the generator output controller. detecting element which detects
the electrical potential difference,
temperature, and remaining In 1998, developed high power
Series Hybrid capacity. density Li-ion battery for parallel
Electric Vehicle JP10295045 (1997) The battery management provides A controller finds the charging HEV (Jidosha)
an actuator command for control of amount SOC of the battery on
electric power input upon charging the basis of the terminal voltage
the battery pack in response to the VB and the temperature TB of In 1999, developed thermal design
Parallel Hybrid current value of BT (battery the battery. of battery packs for HEV (Japan
Electric Vehicle temperature). Journal of Thermo physical
JP11136808 (1997) A control unit with a microcomputer DC-battery condition distinction Properties,)
controls the charge/discharge of the means distinguish the condition
DC-battery by controlling the of a DC-battery and a generated
Forward citation - generated power of the generator output decision means opt for
JP10295045 (1997) based on the discriminated results the generated output by the In 2000, developed electric double
of the state of the DC-battery. engine driven generator based layer capacitor for HEV with high
on the distinction result by the charge/discharge efficiency at high
Year # power density (Jidosha)
dc-battery condition distinction
1998 4 means.
US6452286 (1999) Control unit - Microprocessor Charging current detecting unit
1999 4 detects the actual charging
(42 V)
current of the motor-generator
2000 3 and actual charging current to
the high voltage battery by a In 2003 Nissan propose a new HEV
2001 7 current sensor. charge/discharge control system
based on car navigation information.
2002 2 JP2001268707 (2000) The charge of a DC-battery is When start conditions are met,
(Proceedings: JSAE Annual
restricted to a proper amount by the charging level SOC of the
(42 V) Congress)
restricting the IC engine output battery is detected by the current
torque, if the charging level SOC is sensor.
higher than a given value.
 NISSAN MOTORS - Technology approach

Various Methods of
Event Output Effect Action
Power Management

Generator control unit allows charging

to permit amount and controls
deceleration from becoming too large.

JP2001078306 (1997)
Regenerative braking The battery management system
provides an actuator command for
control of electric power input upon
JP10295045 (1997) charging the battery pack in response
Regenerative barking to the current value of BT

Restricting the charge of DC-battery

JP2001268707 (1996) Power generated/ Overcharge to a proper amount by restricting the
Restarted after an Power management
consumed IC engine output torque.
idiling stop released Over discharge

JP10084636 (1995) Controlling the max. power generation

High speed output of generator and max. number
of rotations of engine depending on
the battery condition.
JP11136808 (1994)
High speed &
regenerative braking A control unit with a microcomputer
controls the generated power of the
engine-drive generator based on the
discriminated results of the state of
the DC-battery.
 Findings

• JP10295045 (1997):- Battery management system, received 21 forward

citations from all big names in a span of 5 years and self- cited twice the
same technology indicating strong technology strength and building on
its own technology.

• Patent and non-patent information indicate that Nissan’s has focused

much on circuit arrangements for charging or depolarizing batteries or
for supplying loads from batteries (H02J 7/00)

• Jointly worked with Sony corp. (1998) developing high power density
Li-ion battery for parallel HEV

• Proposed a novel charge/discharge control system based on car

navigation information.