Process for Auto-Testing a Fully Discharged Battery, Such as Double-Layer Capacitor Battery, and Circuit for Doing the Same

Abstract

A process for performing an auto-test of a fully discharged battery of an electronic appliance including a battery charger, said process involving the steps of : performing an initialization phase; charging said battery with a predetermined constant current during a predefined period allowing stabilization of said current (Icurrent); detecting the voltage of said battery after said predefined period, said battery being still in charge; testing whether said sensed voltage is comprised within a predetermined range of threshold values (V1, V2), and reporting a battery failure when said sensed value is outside said range. The invention is particularly adapted to the auto-test of a backup battery made of Electric double layer capacitors or any fully discharged backup battery.

What is claimed is: 
     
         1 . A method of auto-testing a fully discharged battery of an electronic appliance that includes a battery charger, comprising:
 configuring a circuit to test any one of a lithium-ion, nickel-cadmium, and electric double-layer capacitor type battery used in an electric appliance;   performing an initialization phase;   charging the battery with a predetermined constant current during a predefined period having a duration that allows stabilization of the current;   detecting a voltage of the battery after the predefined period, while the battery is still being charged;   determining whether the detected voltage is within a predetermined voltage range; and   reporting a battery failure responsive to the detected voltage being outside the predetermined voltage range.   
     
     
         2 . The method of  claim 1 , wherein the electronic appliance also includes a processor, and a General Purpose Analog-to-Digital Converter (GPADC) configured to convert the detected voltage into a digital signal and transmit the digital signal to the processor. 
     
     
         3 . The method of  claim 1 , wherein the GPADC is part of a Power Management Unit of the electronic appliance. 
     
     
         4 . The method of  claim 1 , wherein the predefined period is approximately 1 millisecond. 
     
     
         5 . The method of  claim 1 , further comprising:
 reporting that the battery is absent responsive to the detected voltage being equal to a voltage of a power supply of the electronic appliance.   
     
     
         6 . The method of  claim 1 , wherein the detected voltage is calculated as:
     I charge( t )× Z backup( t )+ Vsoc ( t ),
   where Icharge(t) is the current at time t, Zbackup(t) is the internal impedance of the backup battery at time t, and Vsoc(t) is the state of charge of the battery at time t.   
     
     
         7 . The method of  claim 1 , wherein detecting the voltage of the battery after the predefined period is performed by a detection circuit in the electronic appliance. 
     
     
         8 . The method of  claim 1 , wherein the method further comprises:
 detecting a preliminary voltage of the battery after the initialization phase but before the charging has begun.   
     
     
         9 . The method of  claim 8 , wherein the method further comprises:
 subtracting the preliminary voltage from the detected voltage prior to the determining to obtain an adjusted voltage, such that the determining comprises determining whether the adjusted detected voltage is within the predetermined voltage range, and the reporting comprises reporting a battery failure responsive to the adjusted detected voltage being outside the predetermined voltage range.   
     
     
         10 . The method of  claim 1 , wherein the charging the battery during a predefined period having a duration that allows stabilization of the current, also allows stabilization of the voltage. 
     
     
         11 . A circuit for auto-testing a fully discharged battery of an electronic appliance that includes a battery charger, the circuit being configured to:
 test any one of a lithium-ion, nickel-cadmium, and electric double-layer capacitor type battery used in an electric appliance;   perform an initialization phase;   charge the battery with a predetermined constant current during a predefined period having a duration that allows stabilization of the current;   detect a voltage of the battery after the predefined period, while the battery is still being charged;   determine whether the detected voltage is within a predetermined voltage range; and   report a battery failure responsive to the detected voltage being outside the predetermined voltage range.   
     
     
         12 . The circuit of  claim 11 , wherein the appliance includes a processor, and a General Purpose Analog-to-Digital Converter (GPADC) configured to convert the sensed voltage into a digital signal and transmit the digital signal to the processor. 
     
     
         13 . The circuit of  claim 11 , wherein the GPADC is part of a Power Management Unit of the electronic appliance. 
     
     
         14 . The circuit of  claim 11 , wherein the predefined period is approximately 1 millisecond. 
     
     
         15 . The circuit of  claim 11 , wherein the circuit is further configured to:
 report that the battery is absent responsive to the detected voltage being equal to a voltage of a power supply of the electronic appliance.   
     
     
         16 . The circuit of  claim 11 , wherein the detected voltage is calculated as:
     I charge( t )× Z backup( t )+ Vsoc ( t ),
   where Icharge(t) is the current at time t, Zbackup(t) is the internal impedance of the backup battery at time t, and Vsoc(t) is the state of charge of the battery at time t.   
     
     
         17 . The circuit of  claim 11 , wherein a detection circuit for detection of the voltage of the battery is in the electronic appliance. 
     
     
         18 . The circuit of  claim 11 , wherein the circuit is further configured to:
 detect a preliminary voltage of the battery after the initialization phase but before the charging has begun.   
     
     
         19 . The circuit of  claim 18 , wherein the circuit is further configured to:
 subtract the preliminary voltage from the detected voltage prior to the determining to obtain an adjusted voltage, such that the determining comprises determining whether the adjusted detected voltage is within the predetermined voltage range, and the reporting comprises reporting a battery failure responsive to the adjusted detected voltage being outside the predetermined voltage range.   
     
     
         20 . A circuit for auto-testing a fully discharged battery of an electronic appliance that includes a battery charger, the circuit being configured to:
 perform an initialization phase;   charge the battery with a predetermined constant current during a predefined period having a duration that allows stabilization of the current;   detect a voltage of the battery after the predefined period, using a detection circuit in the electronic appliance, while the battery is still being charged;   determine whether the detected voltage is within a predetermined voltage range; and   report a battery failure responsive to the detected voltage being outside the predetermined voltage range.