METHOD OF DETECTING THE END-OF-CHARGE CONDITION OF AN ELECTRIC STORAGE BATTERY UNDER CHARGE AND DEVICE FOR THE CARRYING OUT OF THIS METHOD

• US 3,621,359 A
• Filed: 03/23/1970
• Issued: 11/16/1971
• Est. Priority Date: 03/28/1969
• Status: Expired due to Term

• Current Assignee: Kurt Schnegg
• Original Assignee: Kurt Schnegg
• Inventors: Schnegg, Kurt
• Primary Examiner(s): J. D. Miller
• Assistant Examiner(s): John M. Gunther
• Application Number:
  US05/021,947
• Time in Patent Office: 603 Days
• Field of Search: 320/14,13,21,31,43,32,33,44-45,48,51 340/249 324/29.5
• US Class Current: 320/149
• CPC Class Codes: H02J 7/007182 in response to battery voltage

Abstract

Method and means for detecting the end-of-charge condition of a storage battery under charge comprising periodically interrupting the charging current, maintaining the interruption for a period corresponding to the time constant of the internal resistance of chemical origin of the battery, measuring the voltage of the battery with a voltage test member, applying a resulting electrical magnitude developed by the test member to a thresholdcomparator member which thereupon supplies a signal indicative of whether the electrical magnitude has reached a value determined in the comparator member by a threshold parameter on the basis of which the comparator was adjusted.

Claims

1. A method of detecting the end-of-charge condition of an electric storage battery having a chemically originated internal resistance and being charged, comprising conditioning a threshold-comparator member in accordance with a threshold parameter depending on the value which a battery charging current had prior to interruption of said charging current;

periodically interrupting said charging current;

maintaining each of said interruptions for a period corresponding to at least the order of magnitude of a time constant determined by a parallel resistance-capacitance combination corresponding to said internal resistance of chemical origin of said storage battery;

connecting said storage battery to a voltage-test member adapted to supply an electric magnitude depending on a decrease in voltage of said storage battery, said decrease taking place during each period of interruption, said voltage test member being arranged and operated in such a manner as to cause it to record the value of the voltage of said storage battery just after the start of said interruption of current, whereupon it is caused to read the value of the voltage of said storage battery immediately prior to the end of said interruption, and then cause it to supply said electric magnitude in correspondence with the difference of these two voltage values;

applying said electric magnitude to said threshold-comparator member;

causing a signal to be supplied by said threshold-comparator member to indicate whether said electric magnitude has reached a value determined in said comparator member by said threshold parameter with which it was conditioned.

2. A method of detecting the end-of-charge condition of an electric storage battery having a chemically originated internal resistance and being charged at constant current, comprising conditioning a threshold-comparator member in accordance with a threshold parameter depending on the value which a battery charging current had prior to interruption of said charging current, said parameter remaining constant for the entire duration of a complete charge and corresponding to said constant current;

periodically interrupting said charging current;

maintaining each of said interruptions for a period corresponding to at least the order of magnitude of a time constant determined by a parallel resistance-capacitance combination corresponding to said internal resistance of chemical origin of said storage battery;

connecting said storage battery to a voltage test member adapted to supply an electric magnitude depending on a decrease in voltage of said storage battery, said decrease taking place during each period of interruption, said voltage test member being arranged and operated in such a manner as to cause it to record the value of the voltage of said storage battery just after the start of said interruption of current, whereupon it is caused to read the value of the voltage of said storage battery immediately prior to the end of said interruption, and then cause it to supply said electric magnitude in correspondence with the difference of these two voltage values; and

then cause it to supply said electric magnitude in correspondence with the difference of these two voltage values;

applying said electric magnitude to said threshold-comparator member;

causing a signal to be supplied by said threshold-comparator member to indicate whether said electric magnitude has reached a value determined in said comparator member by said threshold parameter with which it was conditioned.

3. A method of detecting the end-of-charge condition of an electric storage battery having a chemically originated internal resistance and being charged, comprising conditioning a threshold-comparator member in accordance with a threshold parameter depending on the value which a battery charging current had prior to interruption of said charging current;

periodically interrupting said charging current;

maintaining each of said interruptions for a period corresponding to at least the order of magnitude of a time constant determined by a parallel resistance-capacitance combination corresponding to said internal resistance of chemical origin of said storage battery;

connecting said storage battery to a voltage-test member adapted to supply an electric magnitude depending on a decrease in voltage of said storage battery, said decrease taking place during each period of interruption, said voltage test member being arranged and caused to operate in such a manner as to cause it to record the value of the voltage of said storage battery just after the start of said interruption of current, cause it to read the value of the voltage of said storage battery permanently during one entire period of interruption of said charging current and to integrate, as a function of time, the difference between these two voltage values during said entire period, each of said periods of interruption being of equal duration, at least in case of operation at a constant temperature, and cause it to supply the said electric magnitude in correspondence with the integral of the instantaneous values of said difference;

applying said electric magnitude to said threshold-comparator member;

causing a signal to be supplied by said threshold-comparator member to indicate whether said electric magnitude has reached a value determined in said comparator member by said threshold parameter with which it was conditioned.

4. The method according to claim 3 wherein the changes of said internal resistance of chemical origin of said storage battery are compensated by varying an integration factor of said voltage-test member as a function of temperature.

5. The method according to claim 3 wherein the changes of said internaL resistance of chemical origin of said storage battery are compensated by changing, as a function of the temperature, the duration of said period of interruption of current during which the integration of the difference between said two voltage values is effected.

6. A method of detecting the end-of-charge condition of an electric storage battery having a chemically originated internal resistance and being charged at constant current, comprising conditioning a threshold-comparator member in accordance with a threshold parameter depending on the value which a battery-charging current had prior to interruption of said charging current, said parameter remaining constant for the entire duration of a complete charge and corresponding to said constant current;

periodically interrupting said charging current;

maintaining each of said interruptions for a period corresponding to at least the order of magnitude of a time constant determined by a parallel resistance-capacitance combination corresponding to said internal resistance of chemical origin of said storage battery;

connecting said storage battery to a voltage-test member adapted to supply an electric magnitude depending on a decrease in voltage of said storage battery, said decrease taking place during each period of interruption, said voltage-test member being arranged and caused to operate in such a manner as to cause it to record the value of the voltage of said storage battery just after the start of said interruption of current, cause it to read the value of the voltage of said storage battery permanently during one entire period of interruption of said charging current and to integrate, as a function of time, the difference between these two voltage values during said entire period, each of said periods of interruption being of equal duration, at least in case of operation at a constant temperature, and cause it to supply the said electric magnitude in correspondence with the integral of the instantaneous values of said difference;

applying said electric magnitude to said threshold-comparator member;

causing a signal to be supplied by said threshold-comparator member to indicate whether said electric magnitude has reached a value determined in said comparator member by said threshold parameter with which it was conditioned.

7. A device for detecting the end-of-charge condition of an electric storage battery being charged at constant current, comprising means for periodically interrupting a current charging said battery, a threshold-comparator member adapted to define a threshold corresponding during each period of interruption to a parameter determined by the value which said charging current had immediately prior to its interruption;

a voltage-test member adapted to supply to said threshold-comparator member upon each periodic interruption an electric magnitude dependent upon a decrease in voltage in said battery during said interruption; and

means operating as a function of said threshold-comparator member and adapted to interrupt said charging current when said comparator member has supplied a signal indicating that said electric magnitude has reached a value corresponding to a threshold defined in said comparator member, said voltage-test member comprising a two-input differential integrator circuit and a voltage-memorization capacitor connected to one input and adapted so that its voltage becomes substantially identical to that of said storage battery at the start of each period of interruption of the charging current and then remains substantially constant at the value thus acquired without following the change of voltage of the storage battery during the balance of said period;

a second input of said differential integrator circuit being connected to present for said period of interruption a voltage identical to that of said storage battery, an output of said differential integrator circuit being connected to apply an output signal which it bears to said threshold-comparator member, sAid comparator member being adapted to process said output signal as constituting said electric magnitude.

8. A device according to claim 7 wherein said differential integrator circuit has an integration factor which varies as a function of temperature in accordance with the corresponding changes of parameters of said storage battery.

9. A device according to claim 7 wherein said means for periodically interrupting said charging current comprise a programming circuit for determining duration and periodicity of said current interruptions, said programming circuit being adapted to vary the duration of said periods of interruption as a function of temperature in accordance with the corresponding changes of parameters of said storage battery.

10. A device according to claim 7 wherein said threshold-comparator member comprises an adjustable threshold trigger adapted to trigger when said electric magnitude reaches said threshold and to control actuation of a final interruption means of said charging current when said trigger is in a condition resulting from said triggering, said threshold of said trigger is adjustable electronically, and wherein said device comprises automatic means for regulating said threshold as a function of a last value of charging current which has passed therethrough.

11. A device according to claim 7 wherein said threshold-comparator member comprises an adjustable threshold trigger adapted to trigger when said electric magnitude reaches said threshold and to control actuation of a final interruption means of said charging current when said trigger is in a condition resulting from said triggering, said threshold of the said trigger being adjustable manually by means permitting adjustment for the duration of a complete charge of said threshold in correspondence with a constant-charge current.

12. A device for detecting the end-of-charge condition of an electric storage battery being charged, comprising means for periodically interrupting a current charging said battery, a threshold-comparator member adapted to define a threshold which remains constant during the duration of a complete charge and corresponds to a parameter determined by the value of said constant-charging current;

a voltage-test member adapted to supply to said threshold-comparator member upon each periodic interruption an electric magnitude dependent upon a decrease in voltage in said battery during said interruption; and

means operating as a function of said threshold-comparator member and adapted to interrupt said charging current when said comparator member has supplied a signal indicating that said electric magnitude has reached a value corresponding to a threshold defined in said comparator member, said voltage-test member comprising a two-input differential integrator circuit and a voltage memorization capacitor connected to one input and adapted so that its voltage becomes substantially identical to that of said storage battery at the start of each period of interruption of the charging current and then remains substantially constant at the value thus acquired without following the change of voltage of the storage battery during the balance of said period;

a second input of said differential integrator circuit being connected to present for said period of interruption a voltage identical to that of said storage battery, an output of said differential integrator circuit being connected to apply an output signal which it bears to said threshold-comparator member, said comparator member being adapted to process said output signal as constituting said electric magnitude.