A battery pack includes a single cell having a cylindrical shape, the single cell having a positive electrode at one end of the single cell and a negative electrode at the other end of the single cell, a plurality of the single cells being arranged in a radial direction of the single cell; a fuse; a first bus bar connected via the fuse to one electrode, from among the positive electrode and the negative electrode; a second bus bar directly connected to the other electrode, from among the positive electrode and the negative electrode; and a retaining member configured to retain the plurality of single cells from the radial direction of the single cell, in a manner such that when the fuse is disconnected, retaining force with which the single cell is retained by the retaining member decreases and the single cell moves in a direction away from the fuse.

Some embodiments provide energy storage systems that comprise: a first electrode; a second electrode; an electrolyte; the first electrode, the second electrode and the electrolyte are positioned such that the electrolyte is in contact with at least the first electrode; and a polarity reversal system electrically coupled with the first electrode and the second electrode, wherein the polarity reversal system is configured to allow the energy storage system to operate while a first polarity to charge and discharge electrical energy while operating in the first polarity, and the polarity reversal system is configured to reverse the voltage polarity across the first and second electrodes to a second polarity to allow the energy storage system to continue to operate while the second polarity is established across the first electrode and the second electrode to continue to charge and discharge electrical energy while operating in the second polarity.

A secondary battery having improved safety includes an electrode assembly, a case, and a cap assembly. The electrode assembly has first and second non-coating portions. The case accommodates the electrode assembly. The cap assembly includes a cap plate coupled to the case, and first and second collector plates. In the secondary battery, the first and second non-coating portions and the first and second collector plates are connected or coupled by first and second lead tabs, respectively, and the first and/or second lead tabs include a fuse portion.

A PTC device as well as an electrical device such as a battery pack or a dry-cell type secondary cell containing a PTC device and a secondary cell is made more compact. The PTC device includes (1) a PTC component including a laminar polymer PTC element having an electrically conductive filler and a polymer material, and a metal electrode disposed on a surface of each side of the polymer PTC element; and (2) a lead positioned at least in part on the metal electrode of the PTC component, and connected to the metal electrode by an electrically conductive material An exposed part of the electrically conductive material is covered by a protective member including a polypropylene resin, a nylon resin or an epoxy resin.

Two or more module batteries are arranged in an array and connected through wiring. The outer surface of a first side wall of a case faces in a first direction without facing the others of the two or more module batteries. Second and third side walls of the case are spaced from each other in a second direction. The first direction and the second direction are perpendicular to each other. Two or more string groups are arranged linearly in the second direction. The positive electrode current collecting part extends along the inner surface of the second side wall, the positive electrode extension part extends along the inner surface of the first side wall, and the positive electrode feedthrough part penetrates through the first side wall. The positive electrode current collecting part, the positive electrode extension part, the positive electrode feedthrough part, and the wiring are electrically connected to one another.

A protection circuit module which is welded to a connection tab and a PTC device without affecting a printed circuit board, and a battery pack including the same are provided. One embodiment of the present invention provides a battery pack having a bare cell and a protection circuit module electrically connected to the bare cell. The protection circuit module includes a printed circuit board, a connection tab positioned on a bottom surface of the printed circuit board, and a positive temperature coefficient (PTC) device electrically connected to the connection tab. The PTC device has a first lead coupled to a bottom surface of the connection tab, a PTC body electrically connected to the first lead, and a second lead electrically connected to the PTC body.

An apparatus for preventing over-charge for a vehicle battery includes a switch disposed between an adjacent battery cell and a battery cell and closely contact the battery cells when each of the battery cells swell and to form a contact. An inflator is configured to be exploded when the switch is connected. A cushion configured to be disposed between the adjacent battery cell and the battery cell and swells depending on the explosion of the inflator to cut a lead tab which connects the adjacent battery cell and the battery cell.

An internal short-circuit detection method for a battery cell of a battery pack is determined using a battery cell charge balancing resistor and switch. The switch is used for connecting or disconnecting the battery cell charge balancing resistor to the battery cell. Evolution of discharging of the battery with the battery cell-charge balancing resistor connected to the battery cell is monitored to measure an internal short-circuit resistance of the battery cell for estimating the state of the internal short-circuit.

A rechargeable battery includes an electrode assembly including first and second electrodes; a case accommodating the electrode assembly; a cap plate having a short-circuit opening; a first terminal coupled to the first electrode; a second terminal coupled to the second electrode; and a short-circuit member at the cap plate, corresponding to the short-circuit opening, and configured to deform to electrically couple the first and second electrodes; and a short-circuit protrusion at the second terminal and configured to contact the short-circuit member, wherein a surface roughness of the short-circuit protrusion is greater than that of the cap plate.

A secondary battery including an electrode assembly, the electrode assembly including a first electrode, a second electrode, and a separator; a case accommodating the electrode assembly therein; a cell cover sealing the case; and a first terminal unit having one end that is electrically connected to the first electrode of the electrode assembly and having another end extracted to an outside of the case, wherein the first terminal unit includes a first collector in the case and electrically connected to the first electrode of the electrode assembly, the first collector having a fuse area; and an arc cutting block adjacent to the fuse area of the first collector, the arc cutting block being movable to a position previously occupied by the fuse area in the event that the fuse area is cut off, and cutting an arc generation path.