The invention relates to a connection device for an electric accumulator comprising a first connection subassembly associated with one of the electrodes, and a second connection subassembly associated with the other electrode.
Electrical connections for electric accumulators are usually made using connectors that are inserted into electrodes in the form of tabs, or screw-on collars fixed to conducting contacts with opposite polarities. The reliability of the connection interface may be influenced by corrosion or bad tightening, introducing a risk of increasing the electrical resistance. The result is a large voltage drop that reduces the electrical efficiency of the accumulator, and poor dissipation of heat during operation of the accumulator.
The purpose of the invention is to make a connection device for an accumulator in order to obtain high contact quality in the long term, a low voltage drop and protection against electrical overloads and abnormal temperature rises.
The device according to the invention is characterized in that the first connection subassembly comprises:
According to one preferred embodiment, the pins are distributed over the entire surface of the strip that comes into contact with the electrode. Advantageously, the plane surface of the electrode is covered by a soft conducting metal strip, particularly based on lithium, before pressure is applied to the strip to force it into place.
According to one special feature of the invention, the temperature protection means comprise a temperature switch activated by a state change of a paste sensitive to a change in temperature, and return means that pull the switch towards the open position when the temperature exceeds a predetermined limit.
According to one characteristic of the invention, the paste is conducting and is located within the contact gap of the temperature switch.
According to another special feature of the invention, the paste is made of a material that melts under the action of heat.
The electrical protection means comprise an electrical switch comprising a circuit breaker with a rated fuse, formed by a local restriction of the cross section of the conducting path of an electrical connecting part.
Other advantages and characteristics will become clearer from the following description of an embodiment of the invention given as a non-limitative example illustrated in the appended drawings, wherein:
Modular accumulator elements 10 are installed side by side while remaining connected to an electrical connection device, as illustrated in
The first connection subassembly 16 of the anode is arranged to perform an electrical contact resistance function, and a temperature and/or electrical protection function. It comprises a rectangular metallic strip 20 made of a conducting material, with an internal surface on which several pins 22 are formed. The first electrode 12 is covered by a sheet 24 of soft metal, for example lithium, with which this strip 20 comes into contact. The pins 22 are embedded into the first electrode 12, and the soft metal of the sheet 24 deforms under the effect of the mechanical pressure applied from the smooth outside face of the strip 20, so as to create good contact between the anode and the first connection subassembly 16.
The pins 22 distributed on the internal surface of the conducting strip 20 may be made by any process, particularly by stamping or perforating a metal sheet (
Good contact of the strip 20 on the anode guarantees electrical and thermal conductivity of the connection interface, firstly enabling the accumulator element 10 to discharge with maximum electrical efficiency, and secondly dissipation of heat generated by the Joule effect due to permanent current circulation, or an internal defect.
In
The conducting paste 30 in the interval between the curved end bracket 34 of the strip 20 and the connecting part 31 remains in the solid state as long as the temperature remains below the softening threshold. Most of the nominal current that passes through the accumulator element 10 passes through the conducting paste 30 without a significant voltage drop, since the electrical resistance of the steel spring 28 is greater than the resistance of the paste 30.
If the temperature in the controlled area increases, the softening threshold of the paste 30 in the contact gap is exceeded causing expansion of the steel strip spring 28, making the connecting part 31 move along the direction of arrow F opening the contacts delimiting the contact gap. The current then circulates in the steel strip spring 28, and its high electrical resistance reduces the current intensity. Thus, the temperature switch 26 protects the accumulator element 10 whenever the temperature rises due to an internal fault or incorrect use.
The electrical switch 27 in
The two contact gaps of the two switches 26, 27 are connected in series and are activated separately from each other. In one variant embodiment, it is clear that only one electrical breaking zone can be used to perform the temperature and electrical protection functions.
In
In
In the three embodiments in
According to one variant embodiment, the temperature and electrical protections described above may be provided by a single component with an electrical resistance that depends on its internal temperature, for example a positive temperature coefficient, or PTC, resistance in series with the strip 20. This type of component may change from a very low internal resistance to a sufficiently high resistance to limit or interrupt the output current. The energy necessary for this state change may originate either from the environment or the Joule effect.
The second connection subassembly 18 at the cathode end is shown in
Number | Date | Country | Kind |
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01 03093 | Mar 2001 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP02/02282 | 3/4/2002 | WO | 00 | 9/5/2003 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO02/071510 | 9/12/2002 | WO | A |
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20040092167 A1 | May 2004 | US |