US-12627011-B2 - System for protecting a device having variable internal resistance

US12627011B2US 12627011 B2US12627011 B2US 12627011B2US-12627011-B2

Abstract

A system for protecting a device having variable internal resistance includes a protection fuse capable of blowing when a current having an intensity greater than an intensity threshold passes through. The system also includes an estimator suitable for estimating the internal resistance of the device, and a safety device suitable for limiting and/or preventing use of the device when the internal resistance is greater than a resistance threshold beyond which the protection fuse is inoperative.

Inventors

Samuel Cregut
Masato Origuchi
Irina MARINCAS
Antoine Saint-Marcoux

Assignees

RENAULT S.A.S.

Dates

Publication Date: 20260512
Application Date: 20200908
Priority Date: 20190925

Claims (8)

1 . A protection system for an electrochemical cell of a storage battery having variable internal resistance, the electrochemical cell including a casing, a positive terminal connected to a positive electrode, and a negative terminal connected to a negative electrode, the protection system comprising: a switch connected between the positive terminal and the negative terminal, the switch being configured to close in response to an overpressure in the casing, a fuse positioned between the positive terminal and the positive electrode, the fuse being configured to melt when a current of a strength greater than a strength threshold flows through the fuse, circuitry configured to: estimate the internal resistance of said electrochemical cell, compare the internal resistance with a first resistance threshold, a second resistance threshold, and a third resistance threshold, prevent a recharging of said electrochemical cell as soon as said internal resistance is greater than the first resistance threshold chosen such that the electrochemical cell does not have a capacity to melt the fuse above the first resistance threshold, and limit the recharging of said electrochemical cell to a predetermined number of additional charging cycles as soon as said internal resistance is greater than the third resistance threshold chosen such that the electrochemical cell still has the capacity to melt the fuse above the third resistance threshold, the third resistance threshold being less than the first resistance threshold.
2 . The protection system as claimed in claim 1 , wherein the circuitry is configured to estimate said internal resistance only when one or more of the following conditions are met: the electrochemical cell is in a discharging phase, the strength of the current delivered by the electrochemical cell is within a range of predefined values, a variation over time of the strength of the current delivered by the electrochemical cell is greater than a predefined variation threshold, and an internal temperature of said electrochemical cell is within a range of predefined temperatures.
3 . The protection system as claimed in claim 1 , wherein the circuitry is configured to attempt to estimate said internal resistance periodically.
4 . The protection system as claimed in claim 1 , wherein the circuitry is configured to warn a user of an upcoming limitation and/or an upcoming prevention of the use of the electrochemical cell by the circuitry when the internal resistance is greater than the second resistance threshold.
5 . The protection system as claimed in claim 4 , wherein the circuitry is configured to warn the user without limiting the charging of the electrochemical cell when the internal resistance is greater than the second resistance threshold but less than the third resistance threshold.
6 . The protection system as claimed in claim 1 , wherein the circuitry includes a display screen and, when the internal resistance is below the first resistance threshold and above the second resistance threshold, the circuitry is programmed to output a signal to the display screen to display a message that the electrochemical cell will be unusable after the one or two additional recharging cycles.
7 . A storage battery comprising: at least one electrochemical cell equipped with the protection system as claimed in claim 1 .
8 . A method for protecting an electrochemical cell of a storage battery having variable internal resistance, the electrochemical cell including a casing, a positive terminal connected to a positive electrode, and a negative terminal connected to a negative electrode, the electrochemical cell being equipped with a fuse positioned between the positive terminal and the positive electrode and a switch connected between the positive terminal and the negative terminal, the switch being configured to close in response to an overpressure in the casing, the method comprising: estimating the internal resistance of said electrochemical cell, comparing the internal resistance with a first resistance threshold, a second resistance threshold, and a third resistance threshold, preventing recharging of the electrochemical cell as soon as said internal resistance is greater than the first resistance threshold chosen such that the electrochemical cell does not have a capacity to melt the fuse above the first resistance threshold, and limit the recharging of said electrochemical cell to a predetermined number of additional charging cycles as soon as said internal resistance is greater than the third resistance threshold chosen such that the electrochemical cell still has the capacity to melt the fuse above the third resistance threshold, the third resistance threshold being less than the first resistance threshold.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates in general to the safety of storage batteries. It relates more particularly to a protection system for protecting a device having variable internal resistance, such as an electrochemical cell of a storage battery, this protection system comprising a fuse that is able to melt when it is flowed through by a current of a strength greater than a predefined strength threshold. It also relates to a method for protecting such a device. The invention is applied to particular advantage in the production of storage batteries for electric or hybrid vehicles. PRIOR ART Electric and hybrid vehicles are specifically equipped with storage batteries that supply current to electric motors for propelling these vehicles. As taught by document US2017005384, such a storage battery generally comprises a plurality of modules that each incorporate a large number of distinct electrochemical cells. These cells use chemical compounds to store electrical energy, which are potentially hazardous if the cell is overcharged. One common system for safeguarding a storage battery then consists in individually monitoring the voltage across the terminals of each cell and in disconnecting the current in the event of overcharging. Implementing this technical solution unfortunately requires the use of numerous expensive components that are connected redundantly in order to achieve the desired degree of safety. Another solution, described in document US2017005384, consists in equipping each cell with its own integrated safety device. This safety device then comprises firstly a fuse connected between the chemical compounds and the positive terminal of the cell, and secondly a pressure switch connected between the two terminals of this same cell. Thus, in the event of overpressure in the cell, the switch closes, thereby creating a short circuit in the cell and causing the fuse to melt, thus putting the storage battery into a safe state. A first drawback of this solution is that this melting generates an immobilizing breakdown for the vehicle. A second drawback, which the applicant has observed and which proves to be more serious than the first one, is that the fuse does not melt when the cell is short-circuited, generating a risk of the storage battery catching fire or exploding. PRESENTATION OF THE INVENTION In order to remedy the abovementioned drawbacks of the prior art, the present invention proposes to improve the safety of the storage battery by adding a computerized means for detecting the ageing of the battery. More particularly, what is proposed according to the invention is a protection system as defined in the introduction, in which provision is made for estimation means designed to estimate the internal resistance of the device (for example the internal resistance of the electrochemical cell), and safeguarding means designed to limit and/or to prevent the use of this device as soon as said internal resistance is greater than a resistance threshold chosen such that the device still has the capacity to melt the fuse. Specifically, the applicant has observed that, when the state of ageing of an electrochemical cell is advanced, and therefore its internal resistance is excessively high, the electric power able to be developed by this cell is not always sufficient to melt the fuse. Instead of using a smaller fuse (which could be problematic in the event of a high burden on the cell, since the fuse could melt in an unwanted manner), the invention instead proposes to monitor the state of ageing of the cell such that the user is able to be invited, preferably preventively, to have his storage battery serviced before the cell is no longer able to develop the electric power needed to melt the fuse. Other advantageous and non-limiting features of the protection system according to the invention, taken individually or in any technically possible combination, are as follows: said resistance threshold is equal to the internal resistance beyond which the device no longer has the capacity to melt the fuse, to within a safety margin;with said device comprising two electrical connection terminals, provision is made for a switch designed to automatically close the electrical circuit between the two terminals in the event of overpressure in said device;the estimation means are designed to estimate said internal resistance only if one or more or all of the following conditions are met: if the device is in the discharging phase,if the strength of the current delivered by the device is within a range of predefined values,if the variation over time of the strength of the current delivered by the device is greater than a predefined variation threshold,if the internal temperature of said device is within a predefined temperature range; the estimation means are designed to attempt to estimate said internal resistance periodically;the safeguarding means are designed to warn a user of an