Apparatus and method for adjusting charging condition of secondary battery

Patent metadata

Field	Value
Publication number	US-10333180-B2
Application number	US-201615549838-A
Country	US
Kind code	B2
Filing date	Aug 22, 2016
Priority date	Aug 21, 2015
Publication date	Jun 25, 2019
Grant date	Jun 25, 2019

Abstract

An apparatus and method for adjusting a charging condition of a secondary battery are provided. The apparatus includes: a controller configured to receive measurement results from a current measuring unit and a temperature measuring unit of the secondary battery, determine a charging current value and a current temperature value, determine a predicted overheat amount required to raise the temperature of the secondary battery from the current temperature to a threshold temperature for a preset reference time by using a predefined thermodynamic calculation equation, determine a predicted charging current required to generate the predicted overheat amount through charging, determine a predicted charging voltage expected when the predicted charging current flows through an equivalent circuit of the secondary battery, and when a condition of the predicted charging voltage being lower than a preset upper limit charging voltage is satisfied, adjust the upper limit charging voltage such that the upper limit charging voltage is lowered to the predicted charging voltage.

First claim

What is claimed is:

1. An apparatus for adjusting a charging condition of a secondary battery, the apparatus comprising:
a current measuring unit configured to measure a charging current of the secondary battery;
a temperature measuring unit configured to measure a current temperature of the secondary battery; and
a controller coupled to the current measuring unit and the temperature measuring unit,
wherein the controller is configured to receive measurement results from the current measuring unit and the temperature measuring unit to determine a charging current value and a current temperature value, determine a predicted charging current capable of generating, as Joule's heat through an internal resistance of the secondary battery, a heat amount required to raise the temperature of the secondary battery from the current temperature to a threshold temperature for a preset reference time, determine a predicted charging voltage expected when the predicted charging current flows through an equivalent circuit of the secondary battery, and when a condition of the predicted charging voltage being lower than a preset upper limit charging voltage is satisfied, adjust the upper limit charging voltage such that the upper limit charging voltage is lowered to the predicted charging voltage.

2. The apparatus of claim 1 , further comprising:
a switch device provided to a path through which the charging current of the secondary battery flows; and
a voltage measuring unit configured to measure a charging voltage of the secondary battery,
wherein the controller is coupled to the switch device and the voltage measuring unit, and the controller receives measurement results of the voltage measuring unit to determine a charging voltage value of the secondary battery, and when the charging voltage value corresponds to the predicted charging voltage, cuts off the charging of the secondary battery by turning off the switch device.

3. The apparatus of claim 1 , wherein the equivalent circuit comprises a serial resistor, at least one RC circuit, and an open circuit voltage source which varies a voltage thereof depending on a state of charge of the secondary battery, all of which are connected in series.

4. The apparatus of claim 3 , wherein the controller calculates the predicted charging voltage from an equation below:
V=OCV ( z )+ i*R 0+ V 0*exp(− t/RC )+ i*R *(1−exp(− t/RC )).

where i is a current flowing through the equivalent circuit of the secondary battery, R 0 is a resistance value of the serial resistor, R is a resistance value of a resistor included in the RC circuit, C is a capacitance value of a condenser included in the RC circuit, V 0 is an initial voltage value generated from the RC circuit, z is a state of charge of the secondary battery, and OCV(z) is an open circuit voltage corresponding to the state of charge.

5. The apparatus of claim 4 , further comprising a memory unit storing a state of charge-open circuit voltage lookup table, configured to lookup an open circuit voltage from a state of charge,
wherein the controller determines the state of charge of the secondary battery by periodically measuring a charging current or a discharging current of the secondary battery via the current measuring unit and adding up the measured current values using a Coulomb counting method, and determines an open circuit voltage of the secondary battery by mapping the open circuit voltage corresponding to the determined state of charge from the state of charge-open circuit voltage lookup table.

6. The apparatus of claim 1 , further comprising an external temperature measuring unit configured to measure an external temperature of the secondary battery,
wherein the controller determines the external temperature value of the secondary battery by using the external temperature measuring unit, determines a predicted overheat amount Q* required to raise the temperature of the secondary battery from the current temperature to a preset threshold temperature for a preset time based on Equation below, calculates a current value capable of generating the predicted overheat amount Q* as Joule's heat via an internal resistance of the secondary battery, and determines the calculated current value as the predicted charging current:
Q*={T *−( T c −T amb )exp[− t*/mC p R th ]+ T amb }/{R th (1−exp[− t*/mC p R th ])}

where T* is a preset threshold temperature, t* is a reference time, T c is a current temperature of the secondary battery measured by the temperature measuring unit, T amb is an external temperature of the secondary battery measured by the external temperature measuring unit, R th is a preset thermal resistance value between the secondary battery and outside, C p is a preset specific heat under constant pressure of the secondary battery, and m is weight of the secondary battery.

7. The apparatus of claim 1 , further comprising an external temperature measuring unit configured to measure an external temperature of the secondary battery,
wherein the controller determines the external temperature value of the secondary battery by using the external temperature measuring unit, and determines a current value corresponding to a solution approximately satisfying Equation below as the predicted charging current by applying a bisection algorithm to a current variable I of Equation below:

T
*

=

(

T
c

-

T
amb

-

R
th

⁢

I
2

⁢
R

)

⁢

exp
⁡

(

-

t
*

mC
p

⁢

R
th

)

+

T
amb

+

R
th

⁢

I
2

⁢
R

where T* is a preset threshold temperature, t* is a reference time, T c is a current temperature of the secondary battery measured by the temperature measuring unit, T amb is an external temperature of the secondary battery measured by the external

Assignees

• Lg Chemical Ltd

Inventors

• Seo Se-Wook
• Son Sang-Il
• Ko Yo-Han
• Lim Jin-Hyung
• Choi Yong-Seok

Classifications

• B60L58/26

  by cooling · CPC title

• B60L58/15

  Preventing overcharging · CPC title

• B60L58/27

  by heating · CPC title

• H02J2105/37

  exchanging power with electric vehicles [EV] or with hybrid electric vehicles [HEV] · CPC title

• H02J7/963

  in response to battery voltage gradient · CPC title