Electricity: battery or capacitor charging or discharging – Diverse charging or discharging rates for plural batteries
Reexamination Certificate
1999-05-26
2001-08-14
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Diverse charging or discharging rates for plural batteries
C320S152000, C320S167000
Reexamination Certificate
active
06275006
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for charging a secondary battery.
2. Description of the Related Art
Methods for charging a secondary battery can be generally classified into constant-voltage methods and constant-current methods. The constant-current method is capable of rapid charging but is likely to result in overcharging. The constant-voltage method generally controls the charge voltage at a level which is equal to or less than a voltage which causes hydrogen gas generation within the secondary battery. As a result, the charge current decreases as the charging process proceeds, thereby minimizing overcharging.
Thus, the constant-voltage method minimizes overcharging but may result in undercharging. Therefore, methods have been used which combine both the constant-voltage method and the constant-current method.
In the case of combining both the constant-voltage method and the constant-current method, the control voltage, current, and charge time are prescribed so that the proper charge electricity amount equals about 105% to about 120% of the discharged electricity amount.
In recent years, lead-based secondary batteries have replaced conventional liquid-type lead secondary batteries as power sources for various cycle services such as electric automobiles. In particular, lead secondary batteries of a sealed type, which absorb gaseous oxygen generated within the batteries at the negative plates by employing a limited amount of electrolytic solution, have been in use.
Sealed-type lead secondary batteries for cycle services may be subjected to various loads depending on the specific device for which they are used, and various usage time and/or frequency depending on the user. Therefore, the degree of discharge or “discharge depth” which is experienced by sealed-type lead secondary batteries may vary from battery to battery.
It has been discovered that, in the case of aforementioned sealed-type lead secondary batteries for cycle services, merely prescribing a certain charge electricity amount relative to the discharged electricity amount does not allow the sealed-type lead secondary batteries to exhibit desired longevity characteristics.
For example, it to conceivable that a sealed-type lead secondary battery which has not been well-discharged (i.e., “shallowly discharged”) may be charged by using a charger which is intended for a well-discharged (i.e., “deeply discharged”) sealed-type lead secondary battery. Such a charger has a relatively high charge voltage. In such cases, the lifetime of the sealed-type lead secondary battery may be drastically shortened even is a ratio of discharged electricity amount to charge electricity amount within a conventionally acceptable range is prescribed. The problem of such shortened lifetimes becomes especially conspicuous with sealed-type lead secondary batteries employing a Pb—Ca—Sn type alloy (not containing any Sb) as a positive grid alloy and employing a limited amount of electrolytic solution.
Moreover, the above-mentioned problem may unpredictably occur or may not occur at all, depending on the manner in which a given device associated with such a sealed-type lead secondary battery is used by a user. It is practically impossible to select different types of chargers depending on the manner in which a device associated with such a sealed-type lead secondary battery in used by a user.
SUMMARY OF THE INVENTION
A method for charging a secondary battery according to the present invention includes: a first step of precharging the secondary battery; a second step of measuring a first secondary battery voltage Vba
1
after performing the precharging; and a third step of charging the secondary battery based on the measurement of the first secondary battery voltage Vba
1
.
In one embodiment of the invention, the first step includes a fourth step of measuring a second secondary battery voltage Vba
0
prior to the charging of the secondary battery, and the third step includes: a fifth step of comparing the first secondary battery voltage Vba
1
against a first prescribed voltage V
1
, a second prescribed voltage V
2
, and a third prescribed voltage V
3
, where V
3
<V
2
<V
1
; a sixth step of performing a first charging in a first charge mode if the first secondary battery voltage Vba
1
is between and including the first prescribed voltage V
1
and the second prescribed voltage V
2
; a seventh step of performing a second charging in a second charge mode if the first secondary battery voltage Vba
1
is between and including the second prescribed voltage V
2
and the third prescribed voltage V
3
; and an eighth step of performing an active charging if the first secondary battery voltage Vba
1
is lower than the third prescribed voltage V
3
.
In another embodiment of the invention, the eighth step includes: a ninth step of repeating a cycle including the active charging and an ensuing measurement of a third secondary battery voltage Vba
2
, within a predetermined cycle limit, until the third secondary battery voltage Vba
2
becomes higher than the third prescribed voltage V
3
, and performing a second charging in the second charge mode if the third secondary battery voltage Vba
2
becomes higher than the third prescribed voltage V
3
within the predetermined cycle limit; and a tenth step of terminating the charging for the secondary battery if the third secondary battery voltage Vba
2
has not become higher than the third prescribed voltage V
3
within the predetermined cycle limit.
In still another embodiment of the invention, the sixth step includes: a step of subjecting the secondary battery to a constant-voltage charge using a first charge voltage Vch
1
and a step of subjecting the secondary battery to a constant-voltage charge using a second charge voltage Vch
2
after a charge current has decreased to a predetermined value Ia, where Vch
2
<Vch
1
. The seventh step includes: a step of subjecting the secondary battery to a constant-voltage charge using a third charge voltage Vch
3
; an eleventh stop of subjecting the secondary battery to a constant-current charge using a predetermined charge current Ic after the charge current has decreased to a predetermined value Ib, and a step of subjecting the secondary battery to a constant-voltage charge using a charge voltage Vch
4
after the eleventh stop, where Vch
4
<Vch
3
.
In still another embodiment of the invention, the method further includes: a step of terminating the charging for the secondary battery if the first secondary battery voltage Vba
1
measured after performing the precharging is higher than the first prescribed voltage V
1
or if the first secondary battery voltage Vba
1
is lower than a fourth prescribed voltage V
4
, where V
4
<V
3
.
In still another embodiment of the invention, the first stop includes: a step performed in a case where the second secondary battery voltage Vba
0
is equal to or greater than a fifth prescribed voltage V
5
, the stop including: measuring the first secondary battery voltage Vba
1
after the precharging is measured if a charge current Ip during the precharging to equal to or smaller than Imax and equal to or greater than Imin (where Imin>0): displaying a warning message to indicate abnormal operation of a charging device and terminating the charging if the charge current Ip is greater than Imax; or displaying a warning message to indicate abnormality of the secondary battery and terminating the charging if the charge current Ip during the precharging is smaller than Imin; and a step performed in a case where the second secondary battery voltage Vba
0
is lower than the fifth prescribed voltage V
5
, the step including: displaying a warning message to indicate abnormal operation of the charging device and terminating the charging if the charge current Ip to greater than Imax; and measuring the first secondary battery voltage Vba
1
after the precharging if the charge current Ip during the precharging is equal to or smaller than Imax.
In still another embodiment of the inven
Ishiwata Masahito
Jimbo Hiroyuki
Koike Kiichi
Murochi Harumi
Saito Norio
Kelly Michael K.
Matsushita Electric - Industrial Co., Ltd.
Snell & Wilmer L.L.P.
Tibbits Pia
Wong Peter S.
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