Electricity: battery or capacitor charging or discharging – Cell or battery charger structure
Reexamination Certificate
2000-02-14
2002-02-26
Wong, Peter S. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Cell or battery charger structure
C429S099000
Reexamination Certificate
active
06351097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system to recharge batteries (or secondary cell, storage battery) and a method for managing the system. More specifically, the present invention relates to a system and a method for managing rechargeable batteries which are used in various portable electrical equipment such as a wireless radio, an audio tape player, a camera, an electric lamp and so on. In the system the termination voltage is equalized using parallel discharging method before charging the rechargeable battery so that the durability of the rechargeable battery is expanded and the efficiency of the charging is enhanced.
2.Description of the Background Art
The rechargeable battery, so called a secondary battery, or a storage battery is produced and sold in various types and sizes. The typical types of the rechargeable battery includes a nickel cadmium (NiCd) type, a lead-acid type, a nickel metal hydride (NiMH) type, a lithium ion (Li-ion) type, a lithium polymer type, an alkaline type and so on.
These rechargeable batteries should be charged using the appropriate charging method in order that they may be used to their full extent. For example, the NiCd type is preferred to be fully discharged periodically. The Li-ion type, used in notebook computers video cameras, mobile telephones and so on, is preferred to be charged before it is discharged up to the discharge terminal voltage. The lithium polymer type, used in the small electrical devices, the medical equipment, computers and so on, should be always in a charged state before it is exhausted by discharge. The durability of the lithium polymer type could be shortened, if it is fully discharged like nickel cadmium type.
As mentioned above, many rechargeable batteries are not fully utilized and are wasted due to misuse. The wasted rechargeable batteries contributed to environmental pollution, especially, the Ni—Cd type battery, which causes a serious environmental problem due to the toxicity of cadmium. Many countries use their budget and carry out the educational campaign for collecting the used batteries. Furthermore, wasting of the rechargeable batteries unnecessarily consumes natural resource.
Hereinafter, we will focus the Ni—Cd and NiMH type chargeable batteries. Because the Ni—Cd type costs less and is easy to store and deliver as well as being rechargeable in a short time, it is still used in many fields.
Furthermore, it is the best kind of the rechargeable battery in the industrial field because the discharging energy per time is large, it is durable and it can be repeatedly recharged others. It is applied to electrical devices which need significant amount electrical energy such as a flash of a camera, a cordless telephone, a radio, a satellite auxiliary battery, a motor driver, a portable and wireless vacuum cleaner, a diving light, a radio controlled model (car, airplane and ship) and so on.
However, it the Ni-type battery is recharged without deep discharging, the rechargeable capacitance is reduced due to memory effect of crystalizing the un-reacted active materials.
Generally, the rechargeable batteries are used in serial connection with many cells except for the case of using only one cell. In this case, the cells are discharged so that they are in a different energy state. After the cells are used in a serial connection so that, they are discharged in different energy states, the energy state of the cells also become different if they are recharged. If a group of the cells are discharged and recharged many times, then the termination voltage of some cells could be lower than 0.1 volt. In this state, if the user further uses these cells, then the electrical potential is reversed so that these cells are in the battery reversal state.
If the secondary battery which comprises many rechargeable cells having different energy states are connected serially are recharged, then the recharging is stopped when one cell having the most high energy state sends the termination signal to the charger stopping the charge despite that other cells are not charged yet.
On the other hand, in the case of the secondary battery including an over discharged cell, the other cells reach over charged state before the over discharged cell is completely charged. That is, the status of some cells comprised in the secondary battery moves back and forth between the uncompleted charging state and the over discharging (or battery reversal) state. At the same time, the status of the other cells move back and forth between the completed charging state and the uncompleted discharging state. Therefore, all the cells are damaged.
The performance of the Ni-type rechargeable battery can be enhanced by deep discharging periodically so that the crystallized electrolytes are removed. However, the secondary battery generally comprises many cells connected in serial in order to obtain the desired electric voltage for using in the electrical device. Under this state, if one the secondary battery cell is discharged for management, then other cells of the secondary battery can be over discharged or be in the battery reversal state. That is, it is hard to recover or to equalize the cells using the discharging method in the serial connection.
In order to solve the above problem, the individual discharging method is suggested in the U.S. Pat. No. 3,980,940, as shown in FIG.
1
. This conventional invention suggests a method for managing the secondary battery in which the cells are equalized by deep discharging individually before they are recharged in serial connection. The rechargeable batteries (cells)
1
a
,
1
b
,
1
c
and,
1
d
are connected in serial connection. The recharging means
11
is connected to the rechargeable batteries
1
a
to
1
d
. The discharging means
21
comprising the electrical load means
23
a
,
23
b
,
23
c
and
23
d
and discharging blocking switch
25
a
,
25
b
,
25
c
and,
25
d
is connected with the rechargeable batteries
1
a
to
1
d
individually. That is, the electrical load means
23
a
to
23
d
and the discharging blocking switch
25
a
to
25
d
are connected to the rechargeable batteries
1
a
to
1
d
, respectively.
In this conventional invention, each cell
1
a
to
1
d
is discharged individually using the discharging means
21
after the cells are recharged in serial connection using the recharging means
11
.
However, according to the conventional invention, the amount of the energy wastes during individual discharging is very big and it takes a long time to discharge all the cells in different energy state should be fully discharged.
SUMMARY OF THE INVENTION
There is a need for a system and a method in which the rechargeable batteries are equalized without the deep discharging of each battery individually. After that, the charging can be performed for a shorter time period. One object of the present invention is to provide a system and a method for managing the rechargeable batteries in which they are protected from the being damaged due to over discharge or over charge by equalizing the energy difference of the each rechargeable battery.
Another object of the present invention is to provide a system and a method for managing the chargeable batteries in which the rechargeable batteries are discharged in parallel connection for equalizing the energy states of the each battery and then they are recharged in serial connection, so that the discharging efficiency is maximized and the charging is performed quickly.
In order to obtain these objects, the present invention provides a managing system for rechargeable battery comprising a plurality of a rechargeable unit batteries, a closed loop circuit method which connects the cells in parallel connection electrically, an electrical load having regular voltage which is the sum of the maximum output voltage among the plurality of cells and being in parallel connection with the rechargeable cells which are connected in parallel with the closed loop circuit method, a rechargeable battery manager including a discharging
Luk Lawrence
Wong Peter S.
LandOfFree
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