Saft-Societe Des Accumulateurs Fixes Et De Traction

Eric Patry

Pierre Belot

Daniel Lelaidier

After a cell has discharged a quantity Q.sub.o of electricity, charging is controlled by measuring the quantity k Q.sub.o of electricity supplied to the cell, where k is the recharging coefficient and greater than 1. The value of k is varied as an increasing function of the quantity Q.sub.o of electricity discharged, in other words as an increasing function of the relative depth of discharge Q.sub.o /C of the storage cell, where C is its capacity. The state of charge is monitored by generating a magnitude g which is a function of the charging or discharging current. This is done by algebraically integrating the current I over time while using scaling coefficients a=g/I of different values during charging and during discharging. The value of a is varied during charging so that its average value over a complete recharging operation is a decreasing function of the initial depth of discharge from which the recharging operation starts recharging.

Method of controlling the recharging of storage cells, and monitoring

A device for controlling the charging and discharging of a storage battery has an input to which there is applied an input voltage proportional to the magnitude and sign of the current flowing through the battery. The input voltage is amplified and integrated to provide an integral which is an image of the state of charge of the battery. In this invention the input voltage is converted to a pulse train whose frequency is proportional to the magnitude of the input voltage and the pulses are added or subtracted according to its sign. The pulse total forms the said image of the state of charge of the battery.

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Nogent, France

Eric Patry