Special Issue

Automobile Electronics

RelatedRelated productproduct

Battery State Sensor

1.

INTRODUCTION

Recently, the requirements for environmental consideration have been increasing in the automobile industry.
Therefore, optimizing the power management in vehicles
and other correspondence are required to promote theimprovements of the fuel efficiency and the reduction in
CO2 emission.
To deal with them, we have developed a lead-acid battery state sensor with a high-accuracy detection capabilityof the battery states which is a key device in the power
management (Figure 1).
This product monitors the charge/discharge currents,
the voltages and the temperatures in a battery by being
attached to the negative post of a lead-acid battery.
Based on the information, it estimates the battery statessuch as the charging rate (state of charge:SOC) and thedischarging performance (state of function: SOF) accurately. In this way, it contributes to avoiding battery running out, and to the improvement of the fuel efficiency
and reduction in CO2 emission by the charge control andthe stop & start system.

ty) than that of the standard method (it calculates theinternal resistance from the current and the voltage at thestarter starting.). It also measures the internal resistancein hybrid electronic vehicle (HEV) and electric vehicle(EV) which are not equipped with a starter (Table 1). Theinternal resistance has a strong correlation with theengine start-up performance (discharging performance :SOF) (Figure 2).Then this product can estimate the SOF
accurately by high-accurate measurement of the internalresistance.
Table 1

The accuracy of the internal resistance detection.

Item

Our method(Pulse-discharge method)Standard method(Starter method)

Measurement
accuracy± 0.5 mΩ(using actual equipment)

About ± 1.0 mΩ(desktop experiment)

Application toHEV and EV

applicableNot applicable

1211SOF ( V)109876510152025

Internal resistance (mΩ)

Figure 1 The appearance of the developed product.

Figure 2 The internal resistance-SOF correlation.

2.
2.1.

CHARACTERISTICS

A High-accuracy Measurement of the Internal
Resistance of a Battery
This product is “the world’s first” automotive lead-acidbattery state sensor equipped with a pulse discharge circuit. It measures the internal resistance of a battery
actively because the discharge timing can be set arbitrarily. Its measurement accuracy is higher (better repeatabili-2.2.

A Quick and High-accurate Estimation ofthe Battery States
This product can detect the battery states high-accurately
and quickly by sharing the wealth of experience andknowledge regarding automobile lead-acid batteries witha battery manufacturer which is one of our affiliate companies, The Furukawa Battery Co., Ltd. and by developing a unique detection algorithm (Table 2).
Furukawa Review, No. 44

201343

Battery State Sensor

Table 2SOC and SOF detection accuracy.

ItemOur method

SOC detection
accuracy± 10%

About ± 15%(High-speed estimation of stable
OCV*, using actual equipment)(Direct reading of terminal voltage,desktop experiment)

SOF detection
accuracy(Battery voltage at thestart-up of the engine)Standard method± 0.5 V or less

About ± 1.5 V(Impedance active estimation,using actual equipment)(Passive measurement, desktopexperiment)

Negative post of a battery
terminal*Opposite tightening position*OCV: open circuit voltage

Tripolar connector（+B, LIN and for measuring
internal resistance)

73 mm
26 mm

An accurate detection of the SOCs of a battery enables
an optimal charge control in a vehicle, thus contributes tothe improvement of the fuel efficiency.
Also, the SOF becomes an indicator of the discharge
performance. Estimating SOFs accurately enables thejudgment of an engine restart performance, thus leads toaccurate warning of battery running out and to decide
whether to operate stop & start system or not. Therefore
this product prevents battery running out and contributes
to the improvement of the fuel efficiency and the reduction in CO2 emission by stop & start system.

3.

PRODUCT SPECIFICATIONS

The following shows the main specifications of this product.
Table 3

Environmental
property

Electricalproperty

Telecommunication
specification

Stud bolt forground cables
Product dimension: 81 W × 73 L × 26 H mm
Product mass: About 80 g
Figure 3 Product dimension.

Table 4

Evaluated battery.

Type

Manufacturer

Size

Conventional
Liquid type

Furukawa Battery
GS-YUASA
Panasonic
JCI

34B17 〜 80D26
L1 〜 L3

For stop ＆start system

Furukawa Battery
GS-YUASA
Panasonic
Shin-Kobe
JCI

M-42 〜 S-95
L1 〜 L3

UltraBattery

Furukawa Battery

N-55, Q-85, etc.

Product specifications.

Storage temperaturerange-40 – 105℃

4.

Operation
temperature range-40 – 105℃

Operation voltage
range

6 – 16 V

We have succeeded in developing a battery state sensor
which estimates the battery states accurately and quickly
by developing an algorithm and building in a pulse discharge circuit. The product has started mass productionin June, 2012.
In the future, we will promote developing a battery state
sensor which is not limited to a certain battery type (size,manufacturer) by the self-learning function, and which
also can detect the remaining capacity (state of health:SOH).

Current consumption

When operating:
10 mA (Ave.)
When not operating:
1 mA or lessAs per LIN2.0Connector
specification

Tripolar（+B, LIN and for measuring internal resistance)
Terminal size: 0.64 mm, waterproof type

Applicablestandards
of battery posts

JIS D 05301
EN50342-2
IEC60095-2（NORTH AMERICA）

Measurement
Item(Accuracy)

Current: 1 mA – 1500 A < ± 1%>
Voltage: 6 V – 16 V < ± 2%>
Microcomputer temperature:-40℃ - 105℃ < ± 4%>

Detection Item
(Accuracy)

OCV〈± 0.1 V〉
SOC〈± 10％〉
SOF〈± 0.5 V〉
Battery internal resistance < ± 0.5 mΩ>
Battery temperature < ± 10℃ >Productdimension

81 mm

CONCLUSION

For more information, please contact:
Central Japan Sales Dept.
Sales Division
Furukawa Automotive Systems INC.
TEL: +81-565-25-2755 FAX: +81-565-25-2720
e-mail: fws-sales@furukawa.co.jp

81 W × 73 L × 26 H mm（Figure 3）

Product mass

About 80 g

Applicablebattery

See Table 4

Furukawa Review, No. 44

201344