Device and method for measuring the charge state of a nickel-cadmium accumulator

Claim 2

Method for measuring the charge state S of a nickel-cadmium accumulator, comprising the steps of: (a) discharging the nickel-cadmium accumulator with a constant discharge current I; (b) measuring the imaginary portion Z I of the complex impedance of the accumulator at a fixed frequency during discharge; (c) using a quantity proportional to the imaginary portion Z I measured during said discharge as a parameter representative of the charge state of the accumulator, said parameter representative of the charge state being defined by Γ=Z I -2 f -3/2 , where f is said fixed frequency and Z I is the imaginary portion of the complex impedance of the accumulator measured at said fixed frequency during discharge.

Claim 3

Measuring method according to claim 1 further including insuring the validity of the measuring method irrespective of the nominal capacity or commercial origin of the nickel-cadmium accumulator by the steps of adjusting: (a) the discharge current I according to the nominal capacity of the accumulator; (b) the frequency of a disturbing signal according to the nominal capacity and discharge current; (c) the value of a disturbance ΔI applied according to the discharge current I.

Claim 4

Device for measuring the charge state of a nickel-cadmium accumulator, comprising: (a) an intensiostatic circuit enabling the accumulator to be discharged under a test with a constant discharge current I and superimposing on this discharge current an alternative component at a fixed frequency; (b) a conditioner to condition a first signal at the terminals of the accumulator, said first signal consisting of a direct tension of the accumulator and of an alternative tension and having an output terminal; (c) a resistor serially connected to said accumulator; (d) a second signal at the terminals of said resistor, said second signal consisting of the discharge current and of the alternative current; (e) lock-samplers having output terminals to sample a signal at said output terminal of the conditioner; (f) a multiplexer having an output terminal to multiplex signals at an output terminal of the lock-samplers; (g) analog/digital converters to analog/digital convert signals at the output terminal of the multiplexer; and (h) control command means having a program housed in a memory allowing for required sequencing of the lock-samplers, of the multiplexer and of the analog/digital converters, calculation of the imaginary portion of the impedance from digitalized signals and extraction of the value of the charge state.

Claim 5

Device for measuring the charge state of a nickel-cadmium accumulator, comprising: (a) an intensiostatic circuit enabling the accumulator to be discharged under a test with a constant discharge current I and superimposing on this discharge current an alternative component at a fixed frequency; (b) a conditioner to condition a first signal at the terminals of the accumulator, said first signal consisting of a direct tension of the accumulator and of an alternative tension and having an output terminal; (c) a resistor serially connected to said accumulator; (d) a second signal at the terminals of said resistor, said second signal consisting of the discharge current and of the alternative current; (e) lock-samplers having output terminals to sample a signal at said output terminal of the conditioner; (f) a multiplexer having an output terminal to multiplex signals at an output terminal of the lock-samplers; (g) analog/digital converters to analog/digital convert signals at the output terminal of the multiplexer; and (h) control command means having a program housed in a memory allowing for required sequencing of the lock-samplers, of the multiplexer and of the analog/digital converters, calculation of the imaginary portion of the impedance from digitalized signals and extraction of the value of the charge state.

Claim 6

Device according to claim 3 wherein the intensiostatic circuit is a user device functioning on the accumulator so that the discharge current I is fixed by the user device itself.

Claim 7

Device according to claim 3 wherein the said lock-samplers and the multiplexer are comprised of a single electronic component making it possible to have an output proportional to the imaginary portion of the impedance from a voltage input signal and a current input signal.

Claim 8

Device according to claim 3 wherein said control command means is a suitably programmed calculation and external control device.

Claim 9

Device according to claim 3 wherein said device is integrated with the control command means of a system functioning on the accumulator.