Method of charging a secondary battery

• US 5,596,259 A
• Filed: 02/28/1995
• Issued: 01/21/1997
• Est. Priority Date: 02/28/1994
• Status: Expired due to Fees

• Current Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Kokuga, Toshiharu, Mino, Takayuki
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Law, Patrick B.
• Application Number:
  US08/396,308
• Time in Patent Office: 693 Days
• Field of Search: 320/21, 320/22, 320/27, 320/39, 320/48
• US Class Current: 320/157
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A charging apparatus charges a secondary battery, while controlling an output voltage of the charging apparatus to maintain the effective charging voltage at a substantially constant predetermined value at which the secondary battery is actually charged. Such a method prevents the secondary battery from being overcharged with a overvoltage, and enables the charging time to be short.

Claims

1. A method of charging a secondary battery, the method comprising the steps of:

charging the secondary battery with an output voltage (V_out) and a charging current (I), the secondary battery having a loss resistance value (R_val) so that the battery is actually charged with an effective voltage (V_off) described by the following expression;

space="preserve" listing-type="equation">V.sub.off =V.sub.out-( R.sub.val×

I);

sampling a value (I_val) of the charging current (I); and

controlling the output voltage (V_out) to keep the effective voltage (V_off) at a substantially constant predetermined value (V_offval) according to the following expression;

space="preserve" listing-type="equation">(V.sub.offval)=V.sub.out -(R.sub.val ×

I.sub.val).

2.

2. A method according to claim 1, further comprising the steps of:

during charging of the secondary battery, sampling a value (I_val2) of the charging current (I) and a value (V_outval) of the output voltage (V_out);

substantially stopping charging, and sampling a value (V_offval2) of the effective voltage (V_off) of the secondary battery; and

calculating the loss resistance value (R_val) according to the following expression;

space="preserve" listing-type="equation">R.sub.val =(V.sub.outval -V.sub.offval2)/I.sub.val2.

3. A method according to claim 1, further comprising the step of

repeating the steps in claim 1, until the secondary battery is charged at a fully charged state.

4. A method according to claim 1, further comprising the step of charging the second battery with a constant current, before the step in claim 1 of sampling the value (I_val) of the charging current (I).

5. A method of charging a secondary battery, the method comprising the steps of:

generating an output voltage (V_out) and a charging current (I) for the secondary battery which has a loss resistance value (R_val) so that it is actually charged with an effective voltage (V_off) described by the following expression;

space="preserve" listing-type="equation">V.sub.off =V.sub.out -(R.sub.val ×

I);

sampling a value (I_val) of the charging current (I); and

charging the secondary battery by setting the output voltage (V_out) to a value of the following expression;

space="preserve" listing-type="equation">V.sub.out =V.sub.offval +(R.sub.val ×

I.sub.val),

where V_offval is a value of a substantially constant predetermined value.

6. A method according to claim 5, further comprising the steps of:

during charging of the secondary battery, sampling a value (I_val2) of the charging current (I) and a value (V_outval) of the output voltage value (V_out);

substantially stopping charging, and sampling a value (V_offval2) of the effective voltage (V_off) of the secondary battery; and

calculating the loss resistance value (R_val) according to the following expression;

space="preserve" listing-type="equation">R.sub.val=(V.sub.outval -V.sub.offval2)I.sub.val2.

7. A method according to claim 5, further comprising the step of

repeating the steps in claim 5, until the secondary battery is charged at a fully charged state.

8. A method according to claim 5, further comprising the step of charging the secondary battery with a constant current, before the step in claim 5 of sampling the value (I_val) of the charging current (I).

9. A method of charging a secondary battery, the method comprising the steps of:

charging the battery with an output voltage (V_out) and a charging current (I), the secondary battery having a loss resistance value (R_val) so that it is actually charged with an effective voltage (V_off) described by the following expression;

space="preserve" listing-type="equation">V.sub.off =V.sub.out -(R.sub.val ×

I);

sampling a value (I_val) of the charging current (I);

comparing the value (I_val) to a plurality of ranges, each range being defined by a maximum and minimum current value and identifying the range which includes the sampled value (I_val);

charging the secondary battery by setting the output voltage (V_out) to a value of the following expression, within the identified respective range of the charging current (I); and

space="preserve" listing-type="equation">V.sub.out =V.sub.offmax +(R.sub.val ×

I.sub.min),

where I_min is the minimum current value of the identified respective range and V_offmax is a predetermined voltage value.

10. A method according to claim 9, further comprising the steps of:

during charging of the secondary battery, sampling a value (I_val2) of the charging current (I) and a value (V_outval) of the output voltage value (V_out);

substantially stopping charging, and sampling a value (V_offval) of the effective voltage value (V_off) of the secondary battery; and

calculating the loss resistance value (R_val) according to the following expression;

space="preserve" listing-type="equation">R.sub.val =(V.sub.outval -V.sub.offval)/I.sub.val2.

11. A method according to claim 9, further comprising the step of

repeating the steps in claim 9, until the secondary battery is charged at a fully charged state.

12. A method according to claim 9, further comprising the step of charging the secondary battery with a constant current, before the step in claim 9 of sampling the value (I_val) of the charging current (I).

13. A method of charging a battery having a loss resistance, the method comprising the steps of:

applying an output voltage to the battery to produce a charging current through the battery which causes a voltage drop across the loss resistance so that the battery is effectively charged at a voltage defined by the difference between the output voltage and the voltage drop; and

controlling the output voltage so that the difference between the output voltage and the voltage drop remains substantially constant.