Rechargeable battery pack

Tuesday, 16 January 2007

Rechargeable battery packs are a packaged assembly of a plurality of interconnected cells or "batteries" that are typically joined together to generate a desired overall voltage potential and current for powering a desired device or system. Rechargeable batteries or secondary batteries have been widely used to provide electrical power for driving battery powered electronic appliances. Battery powered electronic appliances may include, by way of example, MP3 players, laptop computers, camcorders, digital cameras, cell phones, PDAs and other devices. Rechargeable batteries are capable of being charged prior to initial use and recharged after being discharged. Generally, rechargeable batteries are charged by a battery charger having a power supply that can provide a supply of DC current. A rechargeable battery accepts the electrical current and converts it into chemical energy. The remarkable progress in the technology of electronics in recent years has made possible downsizing and weight reduction of electronic apparatuses, and it has resulted in a rapid advancement of cordless and portable operation of the apparatuses. With the advancement of these apparatuses, there is an increased demand for small and lightweight batteries of high energy density, useful as power supplies for the electronic apparatuses. Although a single battery can be employed to power some systems, it is not uncommon for an electronic device to require a battery pack containing several battery cells. Packed rechargeable battery, which has been developed for the purpose of simplifying the handling of a plurality of batteries used in combination as described above, enables a plurality of batteries to be used as a single battery in accordance with various applications by joining them together in a predetermined shape, and has been widespread in recent years. Battery packs containing electrochemical cells are in widespread use with a wide variety of portable electronic devices. Packs are utilized for a variety of reasons, including but not limited to, the ease and efficiency of providing a series or a parallel connection for the cells as part of the pack, depending on the voltage provided by each cell and the power requirements of the device, thereby obviating the need for the device to provide the appropriate cell-to-cell contacts for accepting individual cells.

A battery pack for an assembled battery includes an assembled battery and a case for accommodating the assembled battery therein. The assembled battery is constituted by electrically connecting a plurality of unit cells to one another. Battery packs are typically made by joining one or more component pieces together. Such pack components can include cell receiving sections, one or more end caps and one or more terminals for making electrical connection between the cells and the device. The components may be welded together, adhesively joined together or snap fit together at some point in the manufacturing process. A battery housing or enclosure is typically preformed and expands all dimensions of width, length and height of the battery package compared to the battery cell contained within and carried by the housing. The size of the battery package is further enlarged to accommodate other component parts such as mechanical engaging means to attach the battery package into the cellular phone, electronic circuitry for charging control and battery cell protection, interface contact area to make electrical contact from the battery package to the cellular telephone. The rechargeable battery packs are removable from a battery powered device for a number of reasons. A reason for providing a removable rechargeable battery pack is that one battery pack can be remotely charged while another is being used in the battery powered device. For this purpose, the battery enclosure or casing has guide grooves on both lateral sides thereof engaging with the battery loading device. The output terminal is arranged adjacent to the bottom surface of the casing so that its one end faces a longitudinal lateral side thereof. The battery loading device includes a loading section for loading the battery pack and a terminal for connection to the output terminal of the battery pack. The loading section is formed with a setting surface slightly larger in area than the outer size of the battery pack and on which the bottom surface of the battery pack is set. On the surfaces of the loading section facing both lateral sides of the battery pack are formed guide projections engaged in the guide grooves formed in the battery pack. The terminal section is arranged on the inner rim of the loading section for facing the output terminal of the loaded battery pack. On loading the battery pack on the loading section, the terminal section is connected to the output terminal of the battery pack to permit the power to be supplied. The rechargeable battery case is typically made of a plastic material that is insulating so as not to short to metal electrical contact points. The typical rechargable battery pack case is rectangularly shaped. The growth in the use of portable electronic devices such as, for example cellular phones, personal digital assistants, portable music players, has driven the design of such devices to become smaller and more convenient. Consumers have become accustomed to the convenience and portability of such electronic devices, particularly, cell phones and have demanded that those cell phones become even more convenient and even more portable. The cellular phone housing and the housing of the battery pack powering the cellular telephone have been designed to meet stringent size restrictions and to be as light as possible. Typical battery housings for cellular phones incorporate a plastic case or enclosure for holding the battery cells and often other electrical circuitry components necessary to build-up the complete battery structure to power the phone when the battery housing is engaged with the cellular phone.

A large range of sizes and types of battery packs are produced to power electronic devices. Types of rechargeable battery packs in common use today include nickel-cadmium (NiCd), nickel-metal hydride (NiMH), and the increasingly popular lithium ion type battery. Each of these battery types is generally characterized by a multiplicity of individual cells, each containing the basic electrode/electrolyte combination that produces a discrete voltage potential thereacross. The opposing electrodes of a given number of cells are connected together in series so that the additive effects of the individual cell potentials are combined to produce the overall desired voltage potential for the battery pack. As electronic devices have become highly efficient, downsized, and portable, research and development to enable the battery pack to operate for a long time is actively promoted. For example, a battery pack using lithium ion secondary batteries are of much interest, since it provides a larger energy density compared to conventional battery packs which use lead batteries or nickel-cadmium batteries, and it has little memory effect. Lithium ion secondary batteries are small and lightweight, and can be charged and discharged more than 300 cycles repeatedly. The weight energy density of the lithium ion secondary battery (LIB) is higher than in the nickel-cadmium secondary battery (NiCd) and nickel mercury secondary battery (NiMH). However, the lithium ion secondary battery is in danger of being destroyed due to overcharge and over discharge. Additionally, charge and discharge varies with respect to the individual battery. Accordingly, in order to maintain the safety and reliability, a control circuit for preventing over-charge and over-discharge is generally mounted on BMU (battery management unit) in the battery pack for the purpose of management of battery voltage, etc. It is common that battery packs used in high-performance mobile electronic equipment, such as notebook computers,digital cameras, camcorders, etc., have a SMART (self-monitoring analysis and reporting technology) function of performing a self-diagnosis operation by themselves and, if a problem is forecasted, reporting such a situation to an electronic device. Such battery packs with the SMART function are typically called SMART battery packs. Battery packs for use as power sources in lap computers have a battery charge displaying function and a battery protecting function. Power management systems such as a SMART battery system are constituted in which data including the battery voltage and the battery charge are output to computer bodies through communication buses and the computer bodies control the battery packs. The laptop battery pack includes a rechargeable battery and a protective circuit for protecting the rechargeable battery from overcharging, overdischarging, or other troubles. In the protective circuit, at the instant when even only one of a plurality of rechargeable batteries connected in series with each other drops in voltage below a predetermined level, output is interrupted regardless of the total voltage in order to protect the rechargeable battery. To avoid abrupt power shutdown that may cause data corruption, and therefore power shutdown needs to be made in accordance with a predetermined procedure. A battery pack for use in a notebook computer is equipped with a microcontroller incorporating firmware, thereby constituting an intelligent battery which is connected to a personal computer main body via a communication path.

Rechargeable batteries require an electronic charger for recharging depleted batteries. A battery pack charger has a battery pack loading unit for charging the battery pack loaded therein. In general, the battery pack charging device includes a DC power supply circuit, and a current detection circuit, or a control circuit, enclosed in a housing, and also includes, in the battery loading section, a charging electrode terminal member for connection to a charging terminal member of the battery pack, and a communication terminal for exchanging the information with the battery pack. A typical battery pack charger has open faced surfaces to couple with the rechargeable battery pack. The battery pack charger includes two opposing surfaces one having a positive electrical contact protruding through it and another having a negative electrical contact protruding through it. To engage with a battery pack charger, the rechargeable battery pack is slid against a flat surface of the battery pack charger between the two opposing surfaces, orthogonal to the flat surface and separated by the width of the rechargeable battery pack, in order to make mechanical and electrical connections with the charger. A lock mechanism for holding the loaded state of the battery pack and a popup mechanism for hoisting the battery pack from within the battery pack holding section are provided in the battery pack loading unit of the battery charger. The lock mechanism includes a lock member including a lock part formed at the foremost part thereof and which is slidably mounted in the casing so as to be biased to be protruded into the battery pack loading unit. When the battery pack is loaded in the battery pack loading unit, the lock part of the lock member is engaged in a lock recess formed in the battery pack to keep the loaded state. A battery pack for use as a rechargeable power source of portable terminal equipment such as a cellular phone is provided with a protective circuit for preventing a rechargeable battery from overcharging or overdischarging. Overcharge-preventive mechanism for battery pack comprising a lithium ion secondary battery having a high energy density include those equipped with a heat-sensitive current blocking element for sensing the temperature rise of the battery to restrict the current flow. Specific examples of such a heat-sensitive current blocking element include PTC (positive temperature coefficient) element, thermal fuse, and bimetal device. A battery charger may also be configured as internal charger circuit incorporated into the battery-powered appliance. An internal charger typically begins charging the battery whenever the device is powered by an alternating current (AC) source, and allows discharge of the battery when the AC source is removed. Battery packs of various specifications are manufactured to correspond to electrical equipment parameters such as operating voltage and current. Battery pack characteristics such as output voltage and battery capacity are different for these different battery packs, and during battery charging, optimum charging current and charging time are set for each battery pack. Consequently, many different kinds of battery chargers have been developed to accommodate various battery packs.

Related Information about Rechargeable battery pack