System for protecting a device having variable internal resistance
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.
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.