Abstract: A battery pack for an electric power tool includes a control device that determines the necessity of a balancing control to reduce difference in voltages of cells of a battery based upon voltages of the respective cells measured by a voltage measuring device. The control device controls a subject cell, which is subject to the balancing control to discharge via the discharging device when the balancing control is determined to be necessary. A voltage measuring device measures the voltages of the respective cells when a battery charger detecting device detects the connection of the battery charger in a state where the battery has not been connected to the battery charger for a predetermined specified period of time or more and power feeding to the electric power tool has not been performed for the specified period of time or more.

Abstract: A disclosed heat generation amount estimation unit is used for a battery for an electric power tool, and estimates a heat generation amount of the battery that is a power source of the electric power tool. The heat generation amount estimation unit includes a computation device, and is provided in an apparatus for electric power tool. The computation device periodically reads, either during a discharge from the battery or during a charge to the battery, a detected current from a current detection device, which detects a current corresponding to this point in time from among a discharge current and a charge current flowing through the battery, and adds/subtracts a heat generation amount equivalent value in accordance with a value of the read detected current. The computation device outputs the added/subtracted heat generation amount equivalent value as an estimated value representing the heat generation amount of the battery.

Abstract: A battery pack for electric power tool is provided with a battery and a control circuit. The circuit includes a condition satisfaction determination unit, a continua lion satisfaction determination unit, and a sleep-mode transition unit. The condition satisfaction determination unit determines whether each of at least one predetermined sleep-mode transition condition is satisfied, and determines whether an all-condition satisfaction state is present, which is a state wherein all of the at least one sleep-mode transition condition are satisfied. The continuation satisfaction determination unit determines whether the all-condition satisfaction state has continued for a predetermined. period of time when the condition satisfaction determination unit determines that the all-condition satisfaction state is present, The transition unit stops part of operation of the circuit to shift the circuit to a sleep mode when the continuation satisfaction determination.

Abstract: An internal temperature estimation unit, which reads a detected temperature of a cell of a battery for an electric power tool to estimate an internal temperature of the battery based on the detected temperature, includes: an initial-value setting device which reads, when a discharge/charge of the battery is started, the detected temperature and sets the detected temperature as an initial value; and a temperature increase amount calculation device which calculates a temperature increase amount of the cell of the battery based on a latest value of the detected temperature and the initial value set by the initial-value setting device; the internal temperature estimation unit outputs the temperature increase amount as an estimated value representing the internal temperature of the battery.

Abstract: A battery connection device is provided with an authentication data creating unit that creates authentication data, a conversion unit that performs a first conversion of the authentication data, a transmission unit that transmits the authentication data to a battery pack, a receiving unit that receives from the battery pack a battery-side conversion result that is data obtained after the authentication data is converted by the battery pack, a reverse conversion unit that, on an assumption that the battery pack creates the battery-side conversion result by performing the first conversion and a second conversion on the authentication data, performs a reverse conversion of the second conversion on the battery-side conversion result, and a determination unit that determines whether or not the battery pack is an authentic product by comparing a result of the reverse conversion with a result of the first conversion.

Abstract: A rechargeable battery pack attachable to a power tool includes a display element, a remaining capacity detection device, a remaining capacity display control device, an abnormality detection device, and an abnormality display control device. The display element is provided such that a lighted state thereof can be confirmed from outside. The remaining capacity detection device detects a remaining capacity of a rechargeable battery. The remaining capacity display control device displays the remaining capacity detected by the remaining capacity detection device by controlling the lighted state of the display element. The abnormality detection device detects an abnormality of the rechargeable battery.

Abstract: An information rewriting device includes a first storage unit provided in a battery, a second storage unit provided in a battery charger, and at least one rewrite unit provided in at least one of the battery and the battery charger. When the battery and the battery charger are electrically connected, the at least one rewrite unit rewrites one of a first information stored in the first storage unit and a second information stored in the second storage unit based on the other.

Abstract: Battery charger (10) may include a power source circuit (22) for charging rechargeable batteries (58) when a battery pack (50) is connected directly to the battery charger or is connected thereto with an adapter (30) interposed therebetween. The adapter may include a discharging circuit (42) for discharging the rechargeable batteries. The adapter may also include a switch (48) for alternatively connecting the rechargeable batteries with the discharging circuit or the charging circuit of the battery charger. The battery pack may have a memory (61) storing a flag indicating whether a refresh process is required. The adapter may further include a control portion (41) for controlling the switch. When the battery pack has been connected to the battery charger via the adapter, the control portion may preferably controls the switch on the basis of the flag stored in the memory of the battery pack.

Abstract: A battery pack (1) includes an outer enclosure (2) and a forked air passage (72) for introducing cooling air via the intake port (9) formed in an outer enclosure (2), sending the air between cell groups (70) and (71) which contain cells (14a-14f), and discharging it from the outer enclosure at discharge ports (11). Two metallic radiator plates (73) partially define the air passage so as to be in contact with the side cells (14a-14d), whereas a circular radiator plate (74) made of synthetic resin also partially define the air passage so as to be in contact with the center cells (14e, 14f). The contact areas of the side cells with the metallic radiator plates (73) are varied in order to achieve even cooling of the cells. The upstream portion of the synthetic resin radiator plate has a thicker wall than the downstream portion to achieve the same purpose.

Abstract: Battery charger (10) may include a power source circuit (22) for charging rechargeable batteries (58) when a battery pack (50) is connected directly to the battery charger or is connected thereto with an adapter (30) interposed therebetween. The adapter may include a discharging circuit (42) for discharging the rechargeable batteries. The adapter may also include a switch (48) for alternatively connecting the rechargeable batteries with the discharging circuit or the charging circuit of the battery charger. The battery pack may have a memory (61) storing a flag indicating whether a refresh process is required. The adapter may further include a control portion (41) for controlling the switch. When the battery pack has been connected to the battery charger via the adapter, the control portion may preferably controls the switch on the basis of the flag stored in the memory of the battery pack.