Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Reexamination Certificate
2000-07-05
2001-05-15
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
C324S430000
Reexamination Certificate
active
06232746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a battery charging apparatus and full-charging detecting method, and more particularly to a battery charging apparatus including a full-charging detecting means for detecting the full-charged state of a battery and a method of detecting the full-charged state of the battery.
2. Description of the Related Art
Generally, the battery such as a battery loaded in a vehicle (hereinafter referred to as “in-vehicle battery” will suffer degradation if charging therefor is continued in its full-charged state (remaining level of 100% of the battery). Therefore, in order to prevent the degradation of the battery due to excess charging, it is necessary to detect the full-charged state so that warning informing the full-charged state can be issued, or charging can be automatically stopped.
In order to realize this, a charging/discharging circuit has been proposed in which a battery charging device is built as shown in FIG.
7
.
In
FIG. 7
, a battery charging device
1
includes an AC/DC converter
10
(AC/DC converting means) serving as a DC power source, and a full-charging detecting device
11
serving as a full-charging detecting means. The full-charging detecting device includes a current sensor
101
, a voltage sensor
102
and a microcomputer
103
.
While the in-vehicle battery is charged, the AC/DC converter
10
converts the AC voltage source from an alternator (not shown) into a DC voltage, and also supplies a charging current Ic to the battery B. The charging current Ic is also supplied to the current sensor
101
connected in series with the battery B.
On the other hand, while the in-vehicle battery B is discharged, a discharging current Io discharged from the in-vehicle battery B is supplied to a load
12
and also to the current sensor
101
.
The current sensor
101
detects the charging current Ic supplied to the battery B and the discharging current Io produced therefrom, and supplies the detected values to the microcomputer
103
. The microcomputer
103
is also supplied with the detected value of the terminal voltage across the battery B (hereinafter referred to as a terminal voltage VB) which is detected by the voltage sensor
102
connected in parallel to the in-vehicle battery B.
The microcomputer
103
includes a CPU
103
a
which is operated in accordance with a prescribed control program, an ROM
103
b
which stores the control program for the CPU
103
a
and a prescribed full-charging level, and a RAM
103
c
which temporarily stores the data necessary to perform the computation in the CPU
103
a.
An explanation will be given of the operation of the charging/discharging circuit incorporating the battery charging device
1
having the configuration described above. While the in-vehicle battery B is charged, the CPU
103
a
successively captures the charging current Ic detected by the current sensor
101
and the terminal voltage VB detected by the voltage sensor
102
to compute an electric power (=Ic×VB) and detects an accumulated value of the electric power thus computed as a remaining level. On the other hand, while the battery B is discharged, the CPU
103
a
successively captures the discharging current Ic detected by the current sensor
101
and the terminal voltage VB detected by the voltage sensor
102
and computes an electric power (=Io×VB) on the basis of.them and subtracts an accumulated value of the electric power thus computed from the remaining level.
The CPU
103
a
successively detects the remaining capacity of the in vehicle battery B by the above accumulation system. When the detected remaining capacity exceeds the prescribed full-charged capacity held in the ROM
103
b
, the CPU
103
a
detects that the battery B has reached the full-charged state, and supplies a charging stopping signal Sl to the AC/DC converter
10
. At this time, the AC/DC converter
10
stops supply of the charging current Ic to the battery B.
In short, when the in-vehicle battery B reaches the full-charged state, the AC/DC converter
10
stops to supply the charging current. Thus, the degradation of the battery B due to excess charging can be prevented.
Meanwhile, generally, the in-vehicle battery has a characteristic that it will gradually suffers degradation while the charging/discharging therefor is repeated. Particularly, a Ni-family battery that has been generally used as a battery for an electric vehicle has a great change in the full-charging capacity due to the degradation.
However, when the detected remaining capacity exceeds the prescribed full-charging capacity, the charging/discharging circuit incorporating the conventional battery charging device detects the full-charged state of the battery and simultaneously stops the charging. Therefore, if the actual full-charging capacity of the battery lowers owing to the degradation, the prescribed full-charging capacity becomes larger than the actual full-charging capacity so that the full-charged state of the battery cannot be detected accurately. As a result, when the battery suffers degradation, although the battery has already been fallen in the full-charged state, the remaining capacity in the full-charged sate does not exceed the prescribed full-charging capacity and the charging for the battery is continued. This leads to further degradation of the battery.
Meanwhile, the progression of degradation of the battery is proportional to the using period of the battery. Therefore, in order to obviate the above disadvantage, it can be proposed to form the map data of a plurality of full-charged capacities corresponding to the using period, which are to be used according to the using period. However, this proposal, which requires a memory having a large capacity enough to store a plurality of full-charging capacities, is problematic in terms of cost.
Further, the full-charging capacity of the battery changes with a change in the battery temperature. Specifically, as the battery temperature falls, the full-charging capacity decreases, whereas as the battery temperature rises, the full-charging capacity increases. Therefore, in the conventional battery charging apparatus, the actual full-charging capacity changes according to the battery temperature and hence becomes different from the prescribed full-charging capacity so that the full-charged state of the battery cannot be detected accurately.
Where the battery is successively used in an environment at a high temperature, the actual full-charging capacity increases with a rise in the battery temperature. As a result, although the battery has not been fully charged, the remaining capacity exceeds the prescribed full-charging capacity. Thus, the charging for the battery is stopped since the prescribed full-charging capacity<actual full-charging capacity). On the other hand, where the battery is successively used in the environment at a low temperature, the actual full-charging capacity decreases with a fall in the battery temperature. As a result, although the battery has been already fully charged, the remaining capacity does not exceed the prescribed full-charging capacity. Thus, the charging for the battery is continued by the DC power source since the prescribed full-charging capacity>actual full-charging capacity. This promotes the degradation of the battery.
As described above, the full-charging capacity changes with both the progress of degradation and the temperature of the battery. Therefore, in order to compensate for such changes, it is necessary to measure the using period of the battery and the temperature thereof and acquire the full-charging capacity on the basis of these measured values. This requires complicated control and computation.
SUMMARY OF THE INVENTION
A first object of the invention is to provide a battery charging apparatus which can accurately detect the full-charged state of a battery when it changes owing to degradation of the battery and a method for accurately detecting the full-charged state of the battery using this appara
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Toatley Jr. Gregory J
Tso Edward H.
Yazaki -Corporation
LandOfFree
Battery charging apparatus and full-charging detecting method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Battery charging apparatus and full-charging detecting method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Battery charging apparatus and full-charging detecting method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2556775