BATTERY SOC ESTIMATION PROGRAM, WIRELESS TRANSIT SYSTEM, AND METHOD OF CHARGING THE BATTERY

• US 20090195219A1
• Filed: 11/29/2007
• Published: 08/06/2009
• Est. Priority Date: 11/30/2006
• Status: Active Grant

• Current Assignee: Mitsubishi Heavy Industries Engineering, Ltd. (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Mitsubishi Heavy Industries, Ltd.
• Inventors: Mitake, Masaya, Yamashita, Hiroshi, Yamada, Masaomi, Katahira, Kousuke, Morita, Katsuaki, Yamaguchi, Masahiro
• Granted Patent: US 7,888,912 B2
• Time in Patent Office: Days
• US Class Current: 320/162
• CPC Class Codes: B60L 2260/56 Temperature prediction, e.g. for pre-cooling
• CPC Class Codes: B60L 3/0046 relating to electric energy storage systems, e.g. batteries or capacitors
• CPC Class Codes: B60L 53/11 DC charging controlled by the charging station, e.g. mode 4
• CPC Class Codes: B60L 58/13 Maintaining the SoC within a determined range
• CPC Class Codes: B60L 58/14 Preventing excessive discharging
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables
• CPC Class Codes: H02J 2310/48 for electric vehicles [EV] or hybrid vehicles [HEV]
• CPC Class Codes: H02J 7/0013 acting upon several batteries simultaneously or sequentially H02J7/1423 takes precedence
• CPC Class Codes: H02J 7/00712 the cycle being controlled or terminated in response to electric parameters
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 90/12 Electric charging stations
• CPC Class Codes: Y02T 90/14 Plug-in electric vehicles

Abstract

Occurrence of overcharging and over discharging of batteries mounted on vehicles that travel on predetermined tracks in a wireless transit system is prevented by estimating SOC of the batteries with accuracy. The program in which an equivalent circuit of the battery is set such that the equivalent circuit is composed of three circuit elements connected in series, a first component resistance which is influenced by instantaneous current variation, a component circuit consisting of a capacitance and a second component resistance connected in parallel which is influenced by slow and excessive response, and a terminal voltage of the battery, runs the computer to calculate open circuit voltage of the equivalent circuit using a value of the first component resistance calculated from measurement of current and voltage of the battery and value of k(=the second component resistance/the first component resistance) and τ(=the capacitance×the second component resistance) which are constant values specific to the battery determined based on measurements, and to calculate state of charge of the battery from the open circuit voltage.

Claims

1. A battery SOC estimation program for running a computer to calculate state of charge (SOC) of a battery mounted on a vehicle in a wireless transit system,

wherein an equivalent circuit of the battery is set in the program, the equivalent circuit being composed of three circuit elements connected in series, a first component resistance which is influenced by instantaneous current variation, a component circuit consisting of a capacitance and a second component resistance connected in parallel which is influenced by slow and excessive response, and a terminal voltage of the battery, and

wherein the program runs the computer to calculate open circuit voltage of the equivalent circuit using a value of the first component resistance calculated from measurement of current and voltage of the battery and value of k(=the second component resistance/the first component resistance) and τ

(=the capacitance×

the second component resistance) which are constant values specific to the battery determined based on measurements, and to calculate state of charge of the battery from the open circuit voltage.

2. A wireless transit system for allowing a vehicle mounted with a battery unit and equipped with a computer which operates under a battery SOC estimation program to travel on predetermined tracks by electric power supplied from the battery unit, wherein

ground facilities each comprising a charging power source device and a ground power supply device connected to the charging power source device are established along the predetermined tracks, and

the vehicle is provided with an in-vehicle power receiving device such that the power receiving device faces the ground power supply device when the vehicle makes a stop at a charging position in any of the ground facilities, means to detect current and voltage of the battery unit, a battery SOC calculating means comprising a computer which runs under the battery SOC estimation program according to claim 1, and a charge control device for controlling charging of the battery unit so that the charging of the battery unit is performed by the ground power supply device based on battery SOC calculated by the battery SOC calculating means.

3. A method of charging the battery unit mounted on the vehicle from the ground charging facility in the wireless transit system according to claim 2, wherein charging of the battery unit is performed so that charging current does not exceed an upper limit of charging current determined in consideration of the difference between a predetermined upper limit value and calculated value of open circuit voltage of the battery unit, and charging is stopped when SOC of the battery unit calculated by the battery SOC calculating means reaches a predetermined SOC.