Abstract:
A detecting device and a detecting method for monitoring a battery module are provided. The battery module is electrically connected to a load and includes a first battery unit, a second battery unit and a connecting device. The connecting device connects the positive electrode of the first battery unit to the negative electrode of the second battery unit. The detecting device includes a shunt, a voltage detecting module and a control module. The shunt is serial connected between the battery module and the load to measures the load current. The voltage detecting module measures the voltage difference across the connecting device between the positive electrode and the negative electrode. The control module computes the equivalent resistance across the connecting device between the positive electrode and the negative electrode according to the load current and the voltage difference. Therefore, the hazard caused by aging of the electric circuit can be prevented by monitoring the equivalent resistance, which infers the change of the assembly quality.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a battery module detecting device and a battery module detecting method, and more particularly, to a detecting device and a detecting method of measuring the resistance of the connecting device instantly when the battery module is used, so that the resistance can be an assembly quality indicator of the battery module. 
     2. Description of the Prior Art 
     A battery is a device of converting the energy generated by the chemical reaction into the electrical energy. A single battery unit can only provide a fixed range of voltage depending on the types of its chemical reactions. Therefore, in order to provide a power source of higher voltage or other specific voltage, in practical applications, several battery units are usually connected serially or in parallel to be a battery module, and then the power is outputted. 
     A battery module formed by several battery units connected serially or in parallel. The quality of the battery module depends on not only the quality of the battery units, but also the connection arts between the battery units. In order to obtain the battery module having better quality, the battery units having better quality can be selected in advance to form the battery module. And, the quality of the connection arts between the battery units depends on the skills of assembling and designing the connecting mechanisms between different battery units. 
     In the battery module, the connection between two battery units is achieved by electrically connecting two electrodes having different polarities on different battery units respectively. In detail, the two electrodes can be directly contacted, or connected by a metal rod or wire. If the electrodes are directly contacted, it will be inconvenient for disposing, using, or inspection and maintenance. Therefore, in practical applications, it is common that the battery units are firstly arranged side by side to make the electrodes at the same side, and then the metal connecting rod is used to connect the electrodes. 
     If the metal connecting rod is used to connect the electrodes, the problem that the conduction quality is hard to be controlled must be taken into consideration. More detail, the conditions of oxidation or loosing may be occurred on the contacting points or surfaces between the metal connecting rod and the electrodes of the battery units to cause the increasing of the resistance. In this condition, if the battery module is continued to be used, the temperature of the loosed contacting points or surfaces will be high to cause the fire on the circuit or other electronic hazards. 
     In general, the metal connecting rod is locked on the electrode of the battery unit through the screw; therefore, the assembling quality between the battery units conventionally depends on the locking torque of assembling screw. The larger locking torque of assembling screw usually means firmer locking condition to prevent the increasing of the resistance caused by the shrinking of the contacting area, and the opportunity that the contacting surface of the metal connecting rod and the electrodes can be also reduced to lower the possibility of resistance increased caused by the oxidation of the contacting surface. 
     Since the tiding degree of the screw used to lock the metal connecting rod and electrodes may be changed with time, therefore, the locking quality of the screw must be usually tested to make sure the assembling quality and the using safety of the battery module. However, the locking torque of the screw must be measured under the condition that the battery module is not powered, so that the hazards of an electric shock and a short of the circuit will be prevented. Based on the above-mentioned limitations, it is hard to monitor the assembling quality of the battery module on time when the battery module is used. 
     On the other hand, during the assembling process, there will be some unclean substances (e.g., verdigris or electrolyte) on the surfaces of the metal connecting rod and electrodes to cause the increasing of the contact resistance between the metal connecting rod and electrodes to make the battery module become failure. However, it is hard to measure this variation of resistance by an ordinary low ohmmeter. In detail, the ordinary low ohmmeter is used to measure the resistance of the passive components (e.g., the cable), and its measuring arrange is higher than the milli-ohm level. However, the measuring range of the contacting resistance between the electrodes of the battery and the connecting rod is usually lower than the milli-ohm level. Therefore, it is hard to use the ordinary low ohmmeter to measure the variation of the contacting resistance between the metal connecting rod and electrodes. In addition, the ordinary low ohmmeter is not designed to perform the resistance measurement under the condition that the metal is conducted. Therefore, if the contacting resistance between the metal connecting rod and the electrodes is measured when the battery is powered, it may be very dangerous to use. 
     As mentioned above, the variation of the resistance can not be measured by the low ohmmeter when the battery is powered, and the locking torque variation of the screw can not show the variation of the resistance. Therefore, in practical applications, the locking torque variation of the screw fails to be an ideal quantitative indicator to represent the assembling quality of the battery module, and it also lacks other effective methods to monitor the assembling quality of the battery module instantly. 
     SUMMARY OF THE INVENTION 
     Therefore, a scope of the invention is to provide a battery module detecting method applied to a battery module to solve the above-mentioned problems in prior arts. 
     According to an embodiment, the battery module is electrically connected to a load and includes a first battery unit, a second battery unit, and a connecting device, the connecting device connects a positive electrode of the first battery unit to a negative electrode of the second battery unit. The battery module detecting method includes the following steps. At first, the method measures a voltage difference between the positive electrode and the negative electrode. Then, the method measures a load current of the load. At last, the method computes an equivalent resistance between the positive electrode and the negative electrode according to the load current and the voltage difference. 
     Another scope of the invention is to provide a battery module detecting device applied to a battery module to solve the above-mentioned problems in prior arts. 
     According to an embodiment, the battery module is electrically connected to a load and includes a first battery unit, a second battery unit, and a connecting device, the connecting device connects a positive electrode of the first battery unit to a negative electrode of the second battery unit. The battery module detecting device includes a voltage detecting module, a shunt, and a control module. The voltage detecting module is used for measuring a voltage difference between the positive electrode and the negative electrode. The shunt is serially connected between the battery module and the load and electrically connected to the voltage detecting module. The shunt is used for measuring a load current of the load. The control module is electrically connected to the voltage detecting module and used for computing an equivalent resistance between the positive electrode and the negative electrode according to the load current and the voltage difference. 
     Above all, in the battery module detecting device and the battery module detecting method of the invention, the voltage difference between two electrically connected electrodes on different battery units and the load current of the load can be measured when the battery module is powered. The equivalent resistance between these two electrodes can be instantly computed according to the voltage difference and the load current. This equivalent resistance can effectively show the conduction quality between the connecting device and electrodes, therefore, it can be a quantitative indicator of the battery assembling quality. With the battery module detecting device and the battery module detecting method of the invention, the variation of the equivalent resistance can be instantly observed to rapidly indicate the position that the battery module is poor assembled. Thus, the poor contacting condition can be improved by the user instantly to prevent the accident or damage caused by the poor assembling quality. 
     The objective of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE APPENDED DRAWINGS 
         FIG. 1  shows a scheme diagram of a battery module detecting device in an embodiment of the invention. 
         FIG. 2  shows a scheme diagram of a battery module detecting device in an embodiment of the invention. 
         FIG. 3  shows a flowchart of a battery module detecting method in an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention provides a battery module detecting device and a battery module detecting method for instantly monitoring the assembling quality of the battery module. And, the embodiments of the battery module detecting device and the battery module detecting method of the invention will be shown as follows. 
       FIG. 1  shows a scheme diagram of a battery module detecting device  1   a  in an embodiment of the invention.  FIG. 2  shows a scheme diagram of a battery module detecting device  1   b  in an embodiment of the invention.  FIG. 3  shows a flowchart of a battery module detecting method in an embodiment of the invention. 
     Please refer to  FIG. 1 .  FIG. 1  shows the battery module detecting device  1   a  of the first embodiment of the invention. The battery module detecting device  1   a  is used to test a battery module  2   a , and the battery module  2   a  includes a first battery unit  21 , a second battery unit  22 , and a connecting device  23 . The first battery unit  21  includes a positive electrode  211  and a first output electrode  212  of relative polarity. The second battery unit  22  includes a negative electrode  221  and a second output electrode  222  of relative polarity. The connecting device  23  electrically connects the positive electrode  211  of the first battery unit  21  and the negative electrode  221  of the second battery unit  22 . The connecting device  23  is locked on the positive electrode  211  and the negative electrode  221  via two locking devices  24  respectively. In fact, the locking devices  24  can be a screw or other similar locking components. The battery module  2   a  is electrically connected to a load  3 . More detail, one end of the load  3  is electrically connected to the first output electrode  212  of the first battery unit  21  via a first wire  31 ; another end of the load  3  is electrically connected to the second output electrode  222  of the second battery unit  22  via a second wire  32  and a third wire  33 . 
     The battery module detecting device  1   a  includes a shunt  11 , a voltage detecting module  12 , a control module  13 , and a display  14 . The shunt  11  is serially connected between the battery module  2   a  and the load  3  and electrically connected to the voltage detecting module  12 . The shunt  11  is used for measuring a load current of the load  3 . This load current is the current passing through the connecting device  23 . The voltage detecting module  12  is mainly used for measuring a voltage difference between the positive electrode  211  and the negative electrode  221 . The control module  13  is electrically connected to the voltage detecting module  12  and the display  14  and used for computing an equivalent resistance between the positive electrode  211  and the negative electrode  221  according to the load current and the voltage difference measured and the Ohm&#39;s law formula (V=I*R). In addition, the control module  13  can make the display  14  to show the information related to the battery module  2   a , such as the computed equivalent resistance mentioned above. 
     More detail, the voltage detecting module  12  can further include an analog/digital converter  121 , a millivoltmeter  122 , an analog scanning switch  123 , and a plurality of detecting ends. The plurality of detecting ends can be disposed on the battery module  2   a , the load  3  and any point on the circuit via a detecting end locking device  126  to form the voltage monitoring points. In practical applications, the detecting end locking device  126  can be a screw to lock the detecting ends on the electrodes or other contacting points, or any other kinds of holding devices. The millivoltmeter  122  is used for measuring the voltage difference between the detecting ends (or the voltage detecting points). The analog scanning switch  123  is used for switching the detecting ends measured by the millivoltmeter  122 . The analog/digital converter  121  is used for converting an analog signal measured by the millivoltmeter  122  into a digital signal and transmitting the digital signal to the control module  13 . 
     The plurality of detecting ends includes a first detecting end  124  and a second detecting end  125 . The first detecting end  124  and the second detecting end  125  are electrically connected and fixed on the positive electrode  211  and the negative electrode  221  respectively via the detecting end fixing device  126  to form two voltage monitoring points. By doing so, the millivoltmeter  122  can use the analog scanning switch  123  to select the first detecting end  124  or the second detecting end  125  to measure the voltage difference between the positive electrode  211  and the negative electrode  221 . 
     In addition, the battery module detecting device  1   a  can further include a plurality of protection resistors  127  serially connected between the voltage monitoring points and the voltage detecting module  12 . For example, the protection resistor  127  can be serially connected between the voltage detecting module  12  and the positive electrode  211  or between the voltage detecting module  12  and the negative electrode  221  to prevent the hazard caused by the short when the voltage is measured. In practical applications, the protection resistor  127  can be also serially connected between the detecting ends and the millivoltmeter  122  or the analog scanning switch  123  as shown in  FIG. 1 . 
     By doing so, the battery module detecting device  1   a  can instantly obtain the equivalent resistance of the connecting device  23  when the battery module  2   a  provides power. Since the factors affecting the equivalent resistance includes the resistance of the connecting device  23  itself and the contacting resistance between the connecting device  23  and the positive electrode  211  or the negative electrode  221 , therefore, the equivalent resistance can be used to represent the quantified value of the assembling quality of the connecting device  23 . In the same way, the battery module detecting device  1   a  can further instantly measure the equivalent resistances of the first wire  31 , the second wire  32 , and the third wire  33  via other detecting ends of the voltage detecting module  12 . If any one of the monitored equivalent resistances mentioned above raises suddenly, it means that any one of the contacting points of the corresponding wire has the condition of loosing or aging. 
     Not only instantly measuring the equivalent resistance between the contacting points, the battery module detecting device  1   a  can further have a protection function. In detail, when the battery module  2   a  is initially used or installed, the battery module detecting device  1   a  can ask the control module  13  to record the equivalent resistances between the voltage monitoring points to be a default resistance value. When the battery module  2   a  provides power to the load  3 , the control nodule will continually compute the instant equivalent resistance, and compute a quality reference value according to the default resistance value and the instant equivalent resistance. If the quality reference value is larger than a threshold, the battery module detecting device  1   a  will start a protection function to warn the user the abnormal condition of the circuit. For example, the quality reference value can be the instant equivalent resistance divided by the default resistance value, and the default threshold can be set as 10. When the quality reference value computed is larger than the default threshold, it means that the instant equivalent resistance is 10 times larger than the default resistance value. Thus, the battery module detecting device  1   a  can warn the user through the display  14  or cut off the power provided by the battery module  2   a.    
     In order to explain the advantages of the battery module detecting device of the invention more clearly, the following will be explained cooperated with theorem and data. Please refer to  FIG. 2 ,  FIG. 2  shows the battery module detecting device  1   b  of the second embodiment of the invention. In this embodiment, the battery module  2   b  is formed by six battery units  25  serially connected by the connecting device  26 . The voltage provided by the battery units  25  is 3.33 volts. After the connecting devices  26  are properly disposed on the battery units  25 , each connecting device  26  has the equivalent resistance of 0.2 mΩ. 
     If the current passing through the load  3  is 50 A, according to the power equation: (P=I×V), the total power provided by the battery module  2   b  under the load current 50 A is P 2b =50 A×3.33V×6=999 W. According to the power equation: (P=I 2 ×R), the connecting devices  26  has the initial power P 26 =50 A×50 A×0.2 mΩ=0.5 W. If one of the connecting device  26  is loosed or aged, the equivalent resistance will raise 10 times to be 2 mΩ and its instant consumption power P 26 ′=50 A×50 A×2 mΩ=5 W. In this view point, the consumption power added by the connecting device  26  will be 4.5 W; however, the added proportion is only 0.45% compared to the total power provided by the battery module  2   b . When the battery module  2   b  continually provides power to the load  3 , it is hard to observe so tiny power variation for the load  3 . However, form the view point of the equivalent resistance, the 10 times of the rising of the equivalent resistance can clearly point out the variation of the connecting quality. 
     Please refer to  FIG. 3 ,  FIG. 3  shows the flowchart of the battery module detecting method of an embodiment of the invention. This method can be used to the above-mentioned battery module detecting device  1   a ; therefore, the above-mentioned battery module detecting device  1   a  will be an example as follows to express the flow of the method. 
     As shown in  FIG. 3 , the method of the invention includes the following steps: at first, the first detecting end  124  of the voltage detecting module  12  will be locked on the positive electrode  211 , and the second detecting end  125  will be locked on the negative electrode  221  to form two voltage detecting points (step S 40 ). Then, two protection resistors  127  will be serially connected between the voltage detecting module  12  and the positive electrode  211  and between the voltage detecting module  12  and the negative electrode  221  respectively (step S 41 ) to prevent the hazard caused by the short formed during the process of measurement. Then, the voltage detecting module  12  will be used to measure the voltage difference between the positive electrode  211  and the negative electrode  221  (step S 42 ), and the shunt  11  is used to measure the current passing through the load  3  (step S 43 ). Afterward, the control module  13  will be used to compute an equivalent resistance between the positive electrode  211  and the negative electrode  221  according to the measured voltage difference and the current (step S 44 ). 
     Further, the control module  13  will be used to compute a quality reference value (step S 45 ) according to the equivalent resistance and a default resistance (step S 45 ). The default resistance value can be the equivalent resistance between the positive electrode  211  and the negative electrode  221  measured when the battery module  2   a  does not provide any power. Or the default resistance value can be the equivalent resistance measured by the battery module detecting device  1   a  and detecting method when the battery module  2   a  is assembled and provides power. For example, the quality reference value can be the equivalent resistance minuses the default resistance value, or the equivalent resistance is divided by the default resistance value. 
     Then, the control module  13  is used to compare the quality reference value and a default threshold (step S 46 ). If the quality reference value is larger than the default threshold, the protection function will be started (step S 47 ). In fact, the protection function of the battery module detecting device  1   a  can be shown on the display  14  in the form of text or image, or warned by the default buzzer of the battery module detecting device  1   a . Further, the battery module detecting device  1   a  can also have the cut-off function to stop the power provided by the battery module  2   a  to protect the circuit after the protection function is started. 
     Above all, with the battery module detecting device and the battery module detecting method of the invention, the equivalent resistance of any connecting devices or wires on the battery module and load can be instantly and dynamically computed during the process of using the battery module. By doing so, the inconvenience that the low ohmmeter can not measure the contact resistance of the connecting device can be solved. With monitoring the variation of the equivalent resistance, whether the assembled parts of the battery module are loosed or the contacting resistance becomes larger can be effectively monitored. The invention can be used to the real time detection and monitoring of all kinds of batteries such as the electric vehicle battery, the torpedo batteries, the submarines battery, or any other system using the battery pack as power supply (e.g., the battery pack of UPS). With the battery module detecting device of the invention, the state of the entire battery module can be controlled to prevent the hazard caused by the battery module, so that the cost of maintaining the battery module will be highly reduced and the safety of the battery module will be enhanced. 
     Although the present invention has been illustrated and described with reference to the preferred embodiment thereof, it should be understood that it is in no way limited to the details of such embodiment but is capable of numerous modifications within the scope of the appended claims.