Patent Publication Number: US-2018031637-A1

Title: Battery testing device and method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 105123771 filed in Taiwan R.O.C. on Jul. 27, 2016, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     Technical Field 
     This disclosure relates to a battery testing device and a method thereof, and particularly to a battery testing device and a method thereof which processes a voltage waveform and a current waveform of a subject battery by second-order differential. 
     Related Art 
     A battery usually includes a battery core, a cell shell and an electric power board. The battery core includes electrodes, electrolyte, an isolating film and a pot. With respect to a lithium battery, the isolating film is disposed between the positive electrode and the negative electrode, and these three components are wound together to form a jelly roll. The electrolyte serves as a transmission medium for the lithium ions in the lithium battery. When the lithium battery is charged or discharged, the lithium ions flow through the isolating film to the positive electrode or the negative electrode via the electrolyte. 
     In the manufacturing process of winding the isolating film, positive electrode and negative electrode together to form the jelly roll, the burr of a raw material or an exterior object may lead to a thinned isolating film usually results in an insufficient distance between the positive electrode and negative electrode. When the distance between the positive electrode and negative electrode is insufficient, the capacitance, resistance, withstand voltage or other characteristics of the battery may be affected, thus the outgoing quality of the battery may be decreased. 
     SUMMARY 
     This disclosure provides a battery testing device and a method thereof. 
     According to one or more embodiments of this disclosure, a method for testing a battery includes: providing a constant-current signal to a subject battery; detecting a voltage waveform generated by the subject battery provided with the constant-current signal; switching to a constant-voltage signal to provide the subject battery with the constant-voltage signal when a voltage value of the voltage waveform generated by the subject battery achieves a threshold voltage value; detecting a current waveform generated by the subject battery provided with the constant-voltage signal; processing the voltage waveform and the current waveform by second-order differential to obtain a processed voltage waveform and a processed current waveform respectively; and determining a testing result of the subject battery according to the processed voltage waveform and the processed current waveform. 
     According to one or more embodiments of this disclosure, a battery testing device includes a power supply, a voltmeter, a galvanometer, a differential circuit and an analyzer. The power supply is configured to electrically connect to a subject battery, and to provide a constant-current signal or a constant-voltage signal to the subject battery. The voltmeter is configured to electrically connect to the subject battery and to detect a voltage waveform generated by the subject battery when the power supply provides the constant-current signal to the subject battery. The galvanometer is configured to electrically connect to the subject battery, and to detect a current waveform generated by the subject battery when a voltage value of the voltage waveform achieves a threshold voltage value and the power supply switches to provide the constant-voltage signal to the subject battery. The differential circuit is electrically connected to the voltmeter and the galvanometer, and processes the voltage waveform and the current waveform by a second-order differential to obtain a processed voltage waveform and a processed current waveform respectively. The analyzer is electrically connected to the differential circuit, and determines a testing result of the subject battery according to the processed voltage waveform and the processed current waveform. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only and thus are not limitative of the present disclosure and wherein: 
         FIG. 1  is a functional block diagram of a battery testing device in an embodiment of this disclosure; 
         FIG. 2A-2C  are schematic diagrams of a voltage waveform, a current waveform, and a processed voltage waveform in an embodiment of this disclosure; 
         FIG. 3A-3C  are schematic diagrams of a voltage waveform, a current waveform, and a processed current waveform in another embodiment of this disclosure; 
         FIG. 4A-4C  are schematic diagrams of a voltage waveform, a current waveform, and a processed voltage current waveform in yet another embodiment of this disclosure; and 
         FIG. 5  is a flowchart of a method for testing a battery in an embodiment of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawings. 
     Please refer to  FIG. 1 .  FIG. 1  is a functional block diagram of a battery testing device in an embodiment of this disclosure. As shown in  FIG. 1 , a battery testing device  10  is configured to electrically connect to a subject battery  20  so as to examine the characteristics of the subject battery  20 , such as capacitance, resistance, withstand voltage and so on. The battery testing device  10  includes a power supply  11 , a voltmeter  13 , a galvanometer  15 , a differential circuit  17  and an analyzer  19 . For example and not thus limited, the subject battery  20  may be the final product of a battery, a battery core, a jelly roll of a battery product or other battery-related subjects. 
     The power supply  11  is configured to respectively and electrically connect to the positive electrode and negative electrode of the subject battery  20 , and to supply a constant-current signal or a constant-voltage signal to the subject battery  20 . The voltmeter  13  and the galvanometer  15  are configured to electrically connect to the subject battery  20 , and to respectively detect the voltage waveform and the current waveform generated by the subject battery  20 . In an embodiment, the voltmeter  13  connects to the subject battery  20  in parallel, and the galvanometer  15  and the power supply  11  connect to subject battery  20  in series. This disclosure does not intend to limit the connection scheme of these components. 
     The power supply  11  charges the subject battery  20  by switching between a constant-current mode and a constant-voltage mode. In the constant-current mode, the power supply  11  provides a constant-current signal to the subject battery  20  to charge the subject battery  20  according to the constant-current signal. When the subject battery  20  is charged by the constant-current signal, the voltage difference between the positive electrode and negative electrode of the subject battery  20  increases together with the amount of electric charges stored inside the subject battery  20 . The voltmeter  13  detects a voltage waveform between the positive electrode and the negative electrode, and then transmits the voltage waveform to the differential circuit  17 . 
     When the voltage value of the voltage waveform generated by the subject battery  20  achieves a threshold voltage value, the battery testing device  10  enters a constant-voltage period. In the constant-voltage period, the power supply  11  switches the constant-current signal provided for the subject battery  20  to a constant-voltage signal. Namely, the power supply  11  provides the subject battery  20  with the constant-voltage signal, so that the voltage difference between the positive electrode and negative electrode of the subject battery  20  is kept near a constant value. The galvanometer  15  detects a current waveform generated by the subject battery  20 , and then transmits the current waveform to the differential circuit  17 . In an embodiment, the galvanometer  15  detects the current in a loop circuit between the subject battery  20  and the power supply  11 . 
     The differential circuit  17  is electrically connected to the voltmeter  13 , the galvanometer  15  and the analyzer  19 . The differential circuit  17  obtains the voltage waveform detected by the voltmeter  13  when the constant-current signal is provided to the subject battery  20 , and obtains the current waveform detected by the galvanometer  15  when the constant-voltage signal is provided to the subject battery  20 . In other words, the differential circuit  17  switches between the constant-current mode and the constant-voltage mode. In the constant-current mode, the differential circuit  17  obtains the voltage waveform of the subject battery  20 . In the constant-voltage mode, the differential circuit  17  switches to obtaining the current waveform of the subject battery  20 . The differential circuit  17  processes the voltage waveform and the current waveform by second-order differential, so that if there is an abnormal curve in the voltage waveform or the current waveform, the abnormal curve may be magnified in the processed voltage waveform or the processed current waveform. In the processed voltage or the processed current waveform, the abnormal curve is shown as a pulse with a narrow width and a large variation range, or is shown as another type of waveform which is easily to be identified. The processed voltage waveform and the processed current waveform are transmitted to the analyzer  19  for analysis. The analyzer  19  determines a testing result of the subject battery  20  according to the processed voltage waveform and the processed current waveform. For example, the analyzer  19  is a computer or other device capable of analyzing the processed voltage waveform and the processed current waveform. This disclosure does not intend to limit the type of the analyzer  19 . 
     In practice, the power supply  11  determines whether to switch for providing the constant-voltage signal to the subject battery  20  based on the threshold voltage value. The threshold voltage value is related to the capacitance of a normal battery which is the same type as the subject battery  20 , the maximum amount of electric charges that can be stored in the normal battery or other adequate basis. In an embodiment, the threshold voltage value is the voltage difference between two electrodes of the normal battery wherein the voltage difference is detected when the amount of electric charges stored in the normal battery achieves the maximum amount. 
     With respect to a jelly roll of a battery serving as the subject battery  20  to be tested, the predetermined capacitance of the jelly roll is decided based on the materials of the positive electrode, negative electrode and isolating film, the distance between the positive electrode and negative electrode, the ion concentration of the electrolyte or other factors. The predetermined capacitance indicates the maximum amount of the electric charges which can be stored in the jelly roll. The threshold voltage value can be the voltage difference between the positive electrode and negative electrode of a normal jelly roll, with the voltage difference detected when the normal jelly roll has charged by the constant-current signal until the amount of the electric charges stored in the normal jelly roll achieves the maximum amount. Therefore, in an embodiment, when a subject battery  20  is charged by a constant-current signal but the voltage value of the voltage waveform generated by the subject battery  20  cannot achieve the threshold voltage value, the capacitance of the subject battery  20  is not matched to the predetermined capacitance so that the subject battery  20  is determined as a defective product. 
     Due to the burr of a raw material or an exterior object mixed during the manufacturing process, the distance between the positive electrode and negative electrode of the subject battery  20  may be insufficient; namely, the distance between the two electrodes of the subject battery  20  is shorter than that of a normal battery. Therefore, when the subject battery  20  with the insufficient distance is provided with a constant-current signal, the voltage waveform generated by the subject battery  20  has an abnormal curve. The differential circuit  17  processes the voltage waveform by the second-order differential. In the processed voltage waveform, a pulse is caused by the abnormal curve in the voltage waveform. By identifying a variation range of a pulse in the processed voltage waveform, the analyzer may easily determine the testing result of the subject battery  20 . 
     Similarly, when subject battery  20  with the insufficient distance is provided with a constant-voltage signal, the current waveform generated by the subject battery  20  also has an abnormal curve. The differential circuit  17  processes the current waveform by the second-order differential. In the processed current waveform, a pulse is caused by the abnormal curve in the current waveform. The analyzer  19  may easily determine the testing result of the subject battery  20  according to the processed current waveform. 
     In an embodiment, when the voltage value of the voltage waveform generated by a jelly roll (as the subject battery  20 ) and detected by the voltmeter  13  achieves the threshold voltage, the voltmeter  13  instructs the power supply  11  to switch the mode. The voltmeter  13  is also capable of instructing the power supply  11  to stop or postpone providing the constant-current signal to the jelly roll before the voltage value of the voltage waveform achieves the threshold voltage, in order to avoid the overcharge of the jelly roll. In another embodiment, another type of processor can be included in the battery testing device  10  for determining whether the voltage value of the voltage waveform generated by the jelly roll achieves the threshold voltage value, and for instructing the power supply  11  to switch the mode; it&#39;s not limited in this disclosure. 
     Afterwards, a number of current waveforms, voltage waveforms, a processed voltage waveforms and a processed current waveforms are exemplified. Please refer to  FIG. 1  and  FIG. 2A-2C .  FIG. 2A-2C  are schematic diagrams of a voltage waveform, a current waveform and a processed voltage waveform in an embodiment of this disclosure. As shown in the figures, in a constant-current period P 1 , the power supply  11  provides a constant-current signal to a subject battery  20 , and the voltmeter  13  detects the voltage waveform generated by the subject battery  20 . As shown in the  FIG. 2A , when the voltage value of the voltage waveform generated by the subject battery  20  achieves a threshold voltage h 1 , the battery testing device  10  switches to the constant-voltage mode and enters the constant-voltage period T 1 . The power supply  11  switches to provide a constant-voltage signal to the subject battery  20 , and the galvanometer  15  detects the current waveform generated by the subject battery  20 , as shown in  FIG. 2B . The differential circuit  17  processes the voltage waveform and the current waveform by the second-order differential to obtain the processed voltage waveform and the processed current waveform.  FIG. 2C  shows the processed voltage waveform. The analyzer  19  determines a testing result of the subject battery  20  according to the processed voltage waveform and the processed current waveform. 
     More specifically, in the constant-current period P 1 , the voltage difference between the positive electrode and negative electrode of the subject battery  20  increases with the amount of electric charges stored inside the subject battery  20 . When the distance between the positive electrode and negative electrode of the subject battery  20  is insufficient, the voltage waveform generated by the subject battery  20  has an abnormal curve n 1  during the constant-current period P 1 . For example, the abnormal curve n 1  includes an abnormal decrease of the voltage value due to an abnormal discharge, an arc discharge between electrodes, a damage of the electrode or other factor. At this time, after the differential circuit  17  processed the voltage waveform by the second-order differential, the processed voltage waveform shows a pulse x 1  reflecting the abnormal decrease of the voltage value. The pulse x 1  is more easily to be identified than the abnormal curve n 1  is. According to the pulse x 1 , the analyzer  19  is capable of determining whether the abnormal decrease of the voltage value of the voltage waveform generated by the subject battery  20  falls in an allowable range. In practice, the variation range of the pulse x 1  is related to the abnormal decreasing of the voltage value of the voltage waveform. According to the variation range of the pulse x 1 , the analyzer  19  determines the condition of the electric charges stored in the subject battery  20  stores electric charges as the subject battery  20  being charged. In other words, the voltage waveform of the subject battery  20  is related to the capacitance of the subject battery  20 . 
     In an embodiment, when the analyzer  19  determines that the abnormal decrease of the voltage value of the voltage waveform of the subject battery  20  exceeds the allowable range, the analyzer  19  determines the subject battery  20  as a defective product. For example, an abnormal discharge happens during charging because the distance between the positive electrode and negative electrode of the subject battery  20  is too short. At this time, the subject battery  20  is determined as a defective product. In another embodiment, when the voltage value of the voltage waveform generated by the subject battery  20  cannot achieves the threshold voltage due to the damage of the subject battery  20  caused by an abnormal discharge or another factor, the subject battery  20  is determined as a defective product, and the power supply  11  won&#39;t enter the constant-voltage period T 1 . The power supply  11  does not provide the constant-voltage signal to the subject battery  20  of which the voltage value does not achieve the threshold voltage value. 
     Afterwards, please refer to  FIG. 1  and  FIG. 3A-3C .  FIG. 3A-3C  are schematic diagrams of a voltage waveform, a current waveform and a processed current waveform in another embodiment of this disclosure. As shown in the figures, in a constant-current period P 2 , the power supply  11  provides a constant-current signal to a subject battery  20 , and the voltmeter  13  detects the voltage waveform generated by the subject battery  20 . When the voltage value of the voltage waveform generated by the subject battery  20  achieves a threshold voltage h 2 , the battery testing device  10  switches to the constant-voltage mode and enters the constant-voltage period T 2 . The power supply  11  switches to provide a constant-voltage signal to the subject battery  20 , and the galvanometer  15  detects the current waveform generated by the subject battery  20 . 
     In the constant-voltage period T 2 , a constant-voltage signal is applied to the positive electrode and negative electrode of the subject battery  20 . For example, the voltage value of the constant-voltage signal is set equal to the threshold voltage value. The current in a loop circuit between the subject battery  20  and the power supply  11  decreases with the amount of the electric charges stored in the subject battery  20 . When the distance between the positive electrode and negative electrode of the subject battery  20  is insufficient, the current waveform of the subject battery  20  in the constant-voltage period T 2  has an abnormal curve n 2 . For example, the abnormal curve n 2  includes an abnormal increase of the current value due to an abnormal discharge, an arc discharge between electrodes, a damage of the electrode or other factor. At this time, after the differential circuit  17  processed the current waveform by the second-order differential, the processed current waveform shows a pulse x 2  reflecting the abnormal increase of the current value of the current waveform. The pulse x 2  is more easily to be identified than the abnormal curve n 2  is. According to the pulse x 2 , the analyzer  19  is capable of determining whether the abnormal increase of the current value of the current waveform generated by the subject battery  20  falls in an allowable range. In practice, the variation range of the pulse x 2  is related to the abnormal increasing of the current value of the current waveform. According to the variation range of the pulse x 2 , the analyzer  19  determines the condition of self-discharging of the subject battery  20  in the constant-voltage period T 2 . In other words, the decreasing rate of the current value of the current waveform of the subject battery  20  in the constant-voltage period T 2  is related to an equivalent resistor of the subject battery  20 . 
     Please refer to  FIG. 1  and  FIG. 4A-4C .  FIG. 4A-4C  are schematic diagrams of a voltage waveform, a current waveform and a processed voltage waveform in yet another waveform of this disclosure. As shown in the figures, in a constant-current period P 3 , the power supply  11  provides a constant-current signal to a subject battery  20  for charging. When the voltage value of the voltage waveform of the subject battery  20  achieves the threshold voltage value, an overcharge of the subject battery  20  might happen although the power supply  11  has already stop or postpone providing the constant-current signal to the subject battery  20 . The overcharge is shown as an overcharge curve in  FIG. 4A . When the subject battery  20  is overcharged, the processed voltage waveform has a pulse x 3  reflecting the overcharge, with the processed voltage obtained by processing the voltage waveform by the second-order differential by the differential circuit  17 . In other words, when the analyzer  19  receives the processed voltage waveform from the differential circuit  17 , the analyzer  19  is capable of determining a testing result according to the pulse in the processed voltage waveform. If the pulse in the processed voltage waveform is a positive pulse, the analyzer  19  determines that the voltage value of the voltage waveform increases abnormally. If the pulse in the processed voltage waveform is a negative pulse, the analyzer  19  determines that the subject battery  20  is overcharged. When the variation range of the negative plus x 3  in the processed voltage waveform falls into an allowable range, the overcharge of the subject battery  20  can be ignored. 
     To explain a method for the battery testing device  10  to test a subject battery  20  more specifically, please refer to  FIG. 1  and  FIG. 5 .  FIG. 5  is a flowchart of a method for a battery testing in an embodiment of this disclosure. As shown in the figures, in step S 21 , the power supply  11  provides a constant-current signal to the subject battery  20 . In step S 22 , the voltmeter  13  detects the voltage waveform generated by the subject battery  20 , with the battery provided with the constant-current signal. In step S 23 , when the voltage value of the voltage waveform generated by the subject battery  20  achieves a threshold voltage value, the power supply  11  switches to provide a constant-voltage signal to the subject battery  20 . In step S 24 , the galvanometer  15  detects the current waveform generated by the subject battery  20 , with the subject battery  20  provided with the constant-voltage signal. In step S 25 , the differential circuit  17  processes the voltage waveform and the current waveform by second-order differential. In step S 26 , the analyzer  19  determines a testing result of the subject battery  20  according to the processed voltage waveform and the processed current waveform. The practical method for the battery testing is disclosed in the aforementioned embodiments, so the related details are not repeated in this embodiment. 
     In view of the above description, this disclosure provides a battery testing device and a method for a battery testing. By providing a constant-current signal and switching to provide a constant-voltage signal to a subject battery to be tested when the subject battery is charged, detecting the voltage waveform generated by the subject battery when the subject battery is provided with the constant-current signal, detecting the current waveform generated by the subject battery when the subject battery is provided with the constant-voltage signal and processing the voltage waveform and the current waveform by second-order differential, an abnormal curve in the voltage waveform or the current waveform may be magnified in the processed voltage waveform or the processed current waveform, so that the analyzer may easily analysis the voltage variation and the current variation of the subject battery during the charging according to the processed voltage waveform and the processed current waveform. Therefore, any condition of the subject battery during the charging may be handled, and damage, carbonization of the isolating film or other situation occurring during the charging of the subject battery and resulting in the reduction of the outgoing quality of the subject battery may be avoided.