Patent Publication Number: US-11641043-B2

Title: Electric energy storage device and electric tool system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a continuation application of U.S. patent application Ser. No. 17/344,940 filed Jun. 10, 2021, U.S. Ser. No. 17/344,940 being a continuation application of PCT/CN2019/114230 filed Oct. 30, 2019. PCT/CN2019/114230 is related to and claims the benefit of priority of the following commonly-owned, presently-pending Chinese patent applications: serial No. 201811564074.2, No. 201811564236.2, No. 201811564279.0, No. 201811566089.2, No. 201822145919.6, No. 201822145933.6, No. 201822146566.1, No. 201822146585.4, No. 201822146597.7, all filed Dec. 20, 2018. The disclosures of the forgoing applications are hereby incorporated by reference in their entirety, including any appendices or attachments thereof, for all purposes. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to the field of power tools, in particular to an electric energy storage device and an electric tool system. 
     BACKGROUND 
     In the garden machinery and power tool industry, power tools are generally driven by rechargeable batteries, typically batteries consisting of a plurality of battery, and motors are driven by electrical energy stored in the batteries. After use, the voltage is reduced, the battery pack can be detached from the electric tool, and the external charging device is used for charging the battery pack. 
     The electric tool has a rated working voltage, different electric tools have different rated working voltages, and the output voltage of the battery pack is fixed, so that different battery packs need to be prepared to adapt to the electric tools with different rated working voltages, which the operation is complicated, the cost is increased, and the resource is wasteful. 
     Therefore, it is necessary to design an electric energy storage device and an electric tool system to solve the above problems. 
     SUMMARY 
     This disclosure provides an electric energy storage device which can provide three output voltages, and an electric tool system using the electric energy storage device. 
     To achieve the above object, the disclosure provides the following solution, an electric energy storage device which comprises four energy units with a substantially same voltage value, wherein each energy unit is provided with a positive electrode and a negative electrode, the electric energy storage device comprises a socket, and the socket comprises eight independently arranged electrode terminals; the eight electrode terminals comprise four positive terminals respectively connected with the positive poles of the four energy units and four negative terminals respectively connected with the negative poles of the four energy units. 
     In an embodiment, each electrode terminal is provided with a contact part formed by two arc-shaped elastic arms, and the socket comprises a communication terminal and a charging terminal. 
     In an embodiment, eight of the electrode terminals are evenly distributed into an upper row and a lower row, the polarities of the two electrode terminals corresponding to the upper position and the lower position are the same, and the corresponding two contact parts are vertically aligned. 
     In an embodiment, four electrode terminals located at two outer sides are correspondingly connected with positive electrodes and negative electrodes of two energy units respectively, and four electrode terminals located at the inner sides are correspondingly connected with positive electrodes and negative electrodes of the other two energy units respectively. 
     In an embodiment, the four electrode terminals in the upper row are a fourth negative terminal, a second negative terminal, a third positive terminal, and a first positive terminal, and the four electrode terminals in the lower row are a first negative terminal, a third negative terminal, a second positive terminal, and a fourth positive terminal. 
     In an embodiment, eight of the electrode terminals are arranged in a row and sequentially comprise a fourth negative terminal, a third negative terminal, a second negative terminal, a first negative terminal, a second positive terminal, a third positive terminal, a fourth positive terminal, and a first positive terminal. 
     To achieve the above object, the disclosure provides the following technical solution. An electric tool system includes an electric tool and the above electric energy storage device which is provided with a plug matched with the socket, the plug is provided with a plurality of male terminals, the plurality of male terminals are electrically connected with eight electrode terminals, and the four energy units form one of the following four connection states: a. four energy units are connected in parallel, b. each two of the four energy units are parallel connected first and then series connected therebetween, c. each two of the four energy units are series connected first and then parallel connected therebetween, and d. four energy units are connected in series. 
     In an embodiment, the plug includes a first male blade and a second male blade, the first male blade is connected to the four negative terminals of the four energy units, and the second male blade is connected to the four negative terminals of the four energy units. 
     In an embodiment, the first male blade and the second male blade are each provided with two contact arms, wherein each of the contact arms is in contact with two electrode terminals; or the first male blade and the second male blade are each provided with four contact arms; each of the contact arms is in contact with one of the electrode terminals. 
     In an embodiment, the plug includes a first male blade, a second male blade, and a third male blade, the first male blade is connected to the two negative terminals corresponding to two of the energy units, and the second male blade is connected to the two positive terminals corresponding to the other two energy units, and the third male blade is connected to the remaining four electrode terminals. 
     In an embodiment, the first male blade and the second male blade are each provided with two contact arms, and the third male blade is provided with four contact arms. 
     In an embodiment, the four contact arms of the third male blade are located in a row. 
     In an embodiment, the plug comprises a first male blade, a second male blade, a third male blade, a fourth male blade, and a fifth male blade, wherein the first male blade is connected with a negative terminal corresponding to one energy unit, the fifth male blade is connected with a positive terminal corresponding to the other energy unit, and the second male blade, the third male blade and the fourth male blade are connected with the remaining six electrode terminals in series. 
     In an embodiment, the first male blade and the fifth male blade are each provided with one contact arm, and the second male blade, the third male blade, and the fourth male blade each is provided with two contact arms respectively connected to different electrodes. 
     The disclosure also provides the following technical solution. An electric tool system includes a low-voltage electric tool, a medium-voltage electric tool, and a high-voltage electric tool. The electric tool system further comprises the above electric energy storage device, the low-voltage electric tool is provided with a low-voltage plug, the low-voltage plug cooperates with the socket and the four energy units are parallel connected; the high-voltage electric tool is provided with a high-voltage plug which cooperates with the socket and enables the four energy units are series connected; the medium-voltage electric tool is provided with a medium-voltage plug, and the medium-voltage plug cooperates with the socket and enables the four energy units are connected in a medium-voltage state to provide a medium-voltage. 
     The beneficial effects of the disclosure are: the electric energy storage device has a variety of output voltages, which increases the application range of the electric energy storage device and reduces the cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a parallel circuit diagram of four energy units of the disclosure. 
         FIG.  2    is a circuit diagram showing each two of the four energy units connected in parallel and then connected in series therebetween of the disclosure. 
         FIG.  3    is a circuit diagram showing each two of the four energy units connected in series and then connected in parallel therebetween according to the disclosure. 
         FIG.  4    is a circuit diagram of four energy units in series in the disclosure. 
         FIG.  5    is a perspective view of an electric energy storage device in accordance with the first embodiment of the disclosure. 
         FIG.  6    is a plug-in view of a low voltage plug and a conductive terminal according to the first embodiment of the disclosure. 
         FIG.  7    is a block diagram of the low voltage plug of  FIG.  6   . 
         FIG.  8    is a plug-in view of a medium voltage plug and a conductive terminal according to the first embodiment of the disclosure. 
         FIG.  9    is a structural view of the medium voltage plug of  FIG.  8   . 
         FIG.  10    is a block diagram of one of the medium voltage male blades of  FIG.  9   . 
         FIG.  11    is a plug-in view of a high voltage plug and a conductive terminal according to the first embodiment of the disclosure. 
         FIG.  12    is a structural view of the high voltage plug of  FIG.  11   . 
         FIG.  13    is a block diagram of two of the high voltage male blades of  FIG.  12   . 
         FIG.  14    is a perspective view of an electric energy storage device according to the second embodiment of the disclosure. 
         FIG.  15    is a plug-in view of a low-voltage plug and a conductive terminal according to the second embodiment of the disclosure. 
         FIG.  16    is a block diagram of the low voltage plug of  FIG.  15   . 
         FIG.  17    is a plug-in view of a medium voltage plug and a conductive terminal according to the second embodiment of the disclosure. 
         FIG.  18    is a structural view of the medium voltage plug of  FIG.  17   . 
         FIG.  19    is a plug-in view of a high voltage plug and a conductive terminal. 
         FIG.  20    is a structural view of the high voltage plug of  FIG.  19   . 
     
    
    
     DETAILED DESCRIPTION 
     In order to make objects, aspects, and advantages of the disclosure more apparent, the disclosure will describe in detail with the drawings and specific examples. 
     It should be noted that, in the drawings, wherein only structural and/or process steps have been shown and described in detail that are pertinent to the disclosure, other details that are not pertinent to the disclosure have been omitted so as not to obscure the disclosure with unnecessary detail. 
     Additionally, it should also be noted that the terms “comprises, comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. 
     First Embodiment 
     The disclosure provides an electric energy storage device  100  including four energy units. The voltage value of each energy unit may be substantially the same, meaning that the measured voltage value of each of the four energy units may be nV, or n±5% V. The four energy units can output three different voltages based on different configurations of series or parallel connections: 
     As shown in  FIG.  1   , all four energy units are connected in parallel, and the electric energy storage device  100  may output a low voltage of nV; 
     As shown in  FIG.  2   , the four energy units are divided into two pairs, each pair including two energy units connected in parallel, and the two pairs may then be connected in series. Alternatively, as shown in  FIG.  3   , the four energy units are divided into two pairs, each pair including two energy units connected in series, and the two pairs may then be connected in parallel. In the above two cases, the electric energy storage device  100  may output a medium voltage of 2*nV; 
     As shown in  FIG.  4   , when all four energy units are connected in series, the electric energy storage device  100  may output a high voltage of 4*nV. 
     It should be noted that each of the energy units may be a single battery or other energy carrier, or an electrical combination of multiple batteries or energy carriers (also called as a first string of battery cells, a second string of battery cells, a third string of battery cells, a fourth string of battery cells); the electric energy storage device includes, but is not limited to, a lithium battery, a nickel-hydrogen battery, cadmium nickel batteries, and/or other rechargeable batteries. When a battery is used as an energy unit, the electric energy storage device  100  may also be referred to as a battery pack. 
     As shown in  FIG.  5   , the electric energy storage device  100  may include a housing (not shown) and a socket. Four energy units may be accommodated in the housing (the housing has a battery interface for connecting with the power tools, the battery interface has a latch disposed on the interface for maintaining a mechanical and electrical connection between the battery interface and a power interface of power tools), and the socket is electrically connected with the four energy units. The socket  110  is disposed on one side of the electric energy storage device  100 , and contains a plug interface for connecting with a mating-plug of the power tool. The socket  110  comprises a body  106  and multiple conductive terminals mutually independent of each other and arranged in the body  106 , the conductive terminals are electrically and mechanically connected with a circuit board disposed inside the housing. 
     As shown in  FIG.  6   , the multiple conductive terminals comprise eight electrode terminals each of which is electrically connected to the positive or the negative electrodes of the four energy units. Specifically: the eight electrode terminals include a first positive terminal  111  and a first negative terminal  112  respectively connected to the positive and negative electrodes of the first energy unit; a second positive terminal  113  and a second negative terminal  114  respectively connected to the positive and negative electrodes of the second energy unit; a third positive terminal  115  and a third negative terminal  116  respectively connected to the positive and negative electrodes of the third energy unit; and a fourth positive terminal  117  and a fourth negative terminal  118  respectively connected to the positive and negative electrodes of the fourth energy unit. 
     The conductive terminals may also include a communication terminal  107  and a charging terminal  108  arranged outside the eight electrode terminals. The communication terminal  107  and the charging terminal  108  need to be separately arranged on two opposite ends of the conductive terminals, so that damage to the electric energy storage device caused by high voltage during charging can be prevented, and the service life of the electric energy storage device can be prolonged. 
     In this embodiment, the eight electrode terminals may be evenly distributed into two rows (an upper row and a lower row), and the communication terminal  107  and the charging terminal  108  are respectively arranged on two sides of the two rows of electrode terminals. That is, four electrode terminals located on the outer sides of the upper row and the lower row are connected with positive electrodes and negative electrodes of two energy units, the four electrode terminals located on the inner sides of the upper row and the lower row are connected with positive electrodes and negative electrodes of the other two energy units. Further, the two electrode terminals corresponding to the positive electrodes and the negative electrodes of the same energy unit are arranged in a diagonal relation. Specifically, the electrode terminals in the upper row are, from left to right, a fourth negative terminal  118 , a second negative terminal  114 , a third positive terminal  115 , and a first positive terminal  111 ; the electrode terminals in the lower row are, from left to right, a first negative terminal  112 , a third negative terminal  116 , a second positive terminal  113 , and a fourth positive terminal  117 . 
     Each of the electrode terminals  111 ,  112 ,  113 ,  114 ,  115 ,  116 ,  117 , 118  is provided with a contact part. The contact part comprises two arc-shaped elastic arms which protrude oppositely, and a vertical plugging gap is formed between the two elastic arms, in which a male blade of a connecting plug may be inserted. The polarity of the two electrode terminals corresponding to the positions in the upper row and the lower row may be the same, and the two contact parts are vertically aligned and can be contacted with the same connecting-plug male blade. For example, the fourth negative terminal  118  located at the first position of the upper left row may aligned with the contact part of the first negative terminal  112  located at the first position of the lower left row, and so on. 
     The electric energy storage device  100  of the disclosure is capable of providing energy to a plurality of power tools having different rated voltages, each of the power tools having a corresponding plug that interfaces with a receptacle  110  of the electric energy storage device  100 . The plug may include an insulating base (not shown) and a plurality of male blades mounted on the insulating base (not shown). Different electric tools are provided with different plugs, and different plugs may be provided with male blades in different arrangement states, in order to generate different connection states with the eight electrode terminals of the socket, so that different connection states are formed among the four energy units to form different output voltages. Each of the plugs further includes a communication male blade coupled with the communication terminal  107 , and a charging male blade coupled with the charging terminal  108 . The communication male blade and the charging male blade may not participate in voltage output, so no additional details are disclosed. 
       FIG.  6    shows a situation in which the socket  110  of the electric energy storage device  100  can be configured to insert a low-voltage plug  120  (shown in  FIG.  7   ) of a low-voltage electric tool. 
     As shown in  FIG.  7   , the low-voltage plug  120  includes a communication male blade  124  and a charging male blade  125  located at the two outermost sides, in order to be mated respectively with the communication terminal  107  and the charging terminal  108 . The low-voltage plug  120  further includes two independently disposed low-voltage male blades  121  and  122 . Specifically, the male blade  121  may include two oppositely disposed contact arms  1211 ,  1212 , a connection portion  1213  connects the two contact arms  1211  and  1212 , and a voltage output portion  1214  may be connected to the contact arm  1211  and the contact arm  1212 . The two low-voltage male blades  121  and  122  have a similar structure. Taking the low-voltage male blade  121  as an example, the contact arms  1211  and  1212  are located at the front end, and the voltage output part  1214  are respectively located at the rear end, of the low-voltage male blade  121 . The contact arms  1211  and  1212  and the voltage output part  1214  are vertically arranged, and the voltage output part  1214  and one of the contact arms  1211  and  1212  are located in the same vertical plane. The connection portion  1213  may horizontally connect the bottom edges of the two contact arms  1211 ,  1212  near one side of the voltage output portion  1214  at the middle section of the low-voltage male blade  121 . 
     Referring back to  FIG.  6   , when the socket  110  is mated with the low-voltage plug  120 , each of the contact arms  1211  and  1212  (of the low-voltage male blades  121  and  122 ) may be connected to a corresponding contact portion of two electrode terminals, which are up-down aligned. Specifically, the contact arm  1211  of the low voltage male blade  121  may be plugged into the fourth negative terminal  118  and the first negative terminal  112 , and simultaneously the contact arm  1212  may be plugged into the second negative terminal  114  and the third negative terminal  116 . That is, the low voltage male blade  121  connects the negative electrodes of the four energy units together. 
     The contact arm  1221  of the low voltage male blade  122  may be plugged into the third positive terminal  115  and the second positive terminal  113 , and simultaneously the contact arm  1222  may be plugged into the first positive terminal  111  and the fourth positive terminal  118 . That is, the low voltage male blade  122  connects the positive electrodes of the four energy units together. Thus, the low-voltage male blade  121  and the low-voltage male blade  122  may connect four energy units in parallel, and as shown in  FIG.  1   , and the electric energy storage device  100  may output through two voltage outputs  1214 ,  1224  a low voltage of nV for the low-voltage power tool. 
       FIG.  8    shows a situation in which the socket  110  of the electric energy storage device  100  can be configured to insert a medium voltage plug  130  (shown in  FIG.  9   ) of a medium voltage electric tool. 
     As shown in  FIG.  9   , the medium voltage plug  130  includes a communication male blade (not labeled) and a charging male blade (not labeled) located on the two outermost sides, in order to respectively be mated and plugged into the communication terminal  107  and the charging terminal  108 . The medium voltage plug  130  includes three independently set medium voltage male blades  131 ,  132 ,  133 . The three medium voltage male blades  131 ,  132 ,  133  may be installed on an insulating base (not shown). The medium voltage male blade  131  may include two contact arms  1311 ,  1312 , a connection portion  1313  connecting the two contact arms  1311 ,  1312 , and a voltage output portion  1314  connected with the contact arms  1311  and  1312 . The medium voltage male blade  132  may include two contact arms  1321 ,  1322  opposite to each other, a connection portion  1323  connecting the two contact arms  1321 ,  1322 , and a voltage output portion  1324  connected to the contact arms  1321  and  1322 . The two medium-voltage male blades  131 ,  132  are arranged side by side. 
     The structure of the medium-voltage male blades  131 ,  132  may be substantially the same as that of the low-voltage male blades  121 ,  122  of the low-voltage plug, except that the vertical height may be relatively low. That is, the male blades  131  and  132  may be connected to the four electrode terminals in the lower row of the socket  110 . As shown in  FIG.  10   , the medium-voltage male blade  133  includes four contact arms  1331 ,  1332 ,  1333 ,  1334  arranged side by side, and three connection portions  1335 ,  1336 ,  1337  connecting the adjacent contact arms  1331 ,  1332 ,  1333 ,  1334  in pairs. The medium voltage male blade  133  are provided above the two medium voltage male blades  131 , 132  for connection with the four electrode terminals in the upper row of the socket  110 . 
     Returning to  FIG.  8   , when the socket  110  is mated with the medium voltage plug  130 , the contact arms  1311 ,  1312  of the medium voltage male blade  131  mate respectively with the first and third negative terminals  112  and  116  which are in the lower row. The contact arms  1321 ,  1322  of the medium voltage male blade  132  are respectively plugged into the second positive terminal  113  and the fourth positive terminal  117  located in the lower row. That is, the medium voltage male blade  131  connects two negative electrodes of the first and third energy units in parallel, and the medium voltage male blade  132  connects two positive electrodes of the second and fourth energy units in parallel. 
     The contact arms  1331 ,  1332 ,  1333 ,  1334  of the medium voltage male blade  133  are plugged into four electrode terminals located in the upper row. Specifically, the contact arms  1331 ,  1332  and the connection piece  1335  connect the fourth negative terminal  118  and the second negative terminal  114  of the second group in parallel, and the contact arms  1333 ,  1334  and the connection piece  1337  connect the third positive terminal  115  and the first positive terminal  111  in parallel. In combination with the connection of the two preceding medium voltage male blades  131 ,  132  to the lower electrode terminals, the first and third energy units are already in parallel, and the second and fourth energy units are already in parallel. Finally, the first and third energy units (which are connected in parallel) and the second and fourth energy units (which are connected in parallel) are connected in series through the connection piece  1336  of the medium-voltage male blade  133 , so that each two of the four energy units are connected in parallel and then connected in series therebetween, as shown in  FIG.  2   , the electric energy storage device  100  may output through the two voltage output parts  1314 ,  1324  a medium voltage of 2*nV for the medium-voltage power tool. 
     It can be seen in different embodiments, that the plug can be configured as a combination of male blades in various forms, such that when the plug is mated with the socket  110 , each two of the four energy units are connected in series and then connected in parallel therebetween to output a voltage of 2*nV. Similarly, as shown in  FIG.  3   , the energy units of  FIG.  3    can be viewed respectively from top to bottom as first, third, second, and fourth units. The connection is compared with the connection according to the connection state in  FIG.  3   , which will not be described in detail herein. 
       FIG.  11    shows a situation in which the socket  110  of the electric energy storage device  100  can be configured to insert a high-voltage plug  140  (shown in  FIG.  12   ) of a high-voltage electric tool. 
     As shown in  FIG.  12   , the high-voltage plug  140  includes a communication male blade (not numbered) and a charging male blade (not numbered) which are located at the two outermost sides, in order to respectively be matched and plugged with the communication terminal  107  and the charging terminal  108 . The high voltage plug  140  includes five independently disposed high voltage male blades  141 ,  142 ,  143 ,  144 ,  145  mounted on a base (not shown). The high voltage male blades  142 , 143  are located in the upper row, the high voltage male blades  141 ,  144 ,  145  are located in the lower row, and the high voltage male blade  144  is located between the high voltage male blades  141 , 145 . 
     As shown in conjunction with  FIG.  12    and  FIG.  13   , the high-voltage male blade  141  includes a contact arm  1411  to which the first negative terminal  112  is inserted, and a voltage output portion  1412  is connected to the contact arm  1411 . The high-voltage male blade  145  includes a contact arm  1451  and a voltage output part  1452  connected with the contact arm  1451 , and the contact arm  1451  is in contact with the fourth positive terminal  117 . 
     The high voltage male blade  142  includes two oppositely disposed contact arms  1421 ,  1422 , and includes a connection portion  1423  connecting the contact arms  1421 ,  1422 . The high voltage male blade  143  includes two oppositely disposed contact arms  1431 ,  1432 , and includes a connection portion  1433  connecting the contact arms  1431 ,  1432 . The high voltage male blade  144  includes two oppositely disposed contact arms  1441 ,  144 , and includes a connection portion  1443  connecting the contact arms  1441 ,  1442 . Contact arm  1421  is positioned directly above contact arm  1411 , contact arm  1422  is positioned directly above contact arm  1442 , contact arm  1431  is positioned directly above contact arm  1441 , and contact arm  1432  is positioned directly above contact arm  1451 . 
     Returning to  FIG.  11   , when the socket  110  is paired with the high voltage plug  140 , the contact arm  1411  of the high voltage male blade  141  is in connection with the first negative terminal  112 ; the contact arm  1451  of the high voltage male blade  145  is in connection with the fourth positive terminal  117 . The contact arms  1421 ,  1422  of the high voltage male blade  142  are respectively connected with the fourth negative terminal  118  and the third positive terminal  115 . That is, the positive electrode of the third energy unit and the negative electrode of the fourth energy unit are connected in series. The contact arms  1431 ,  1432  of the high-voltage male blade  143  are respectively connected with the second negative terminal  114  and the first positive terminal  111 . That is, the positive electrode of the first energy unit and the negative electrode of the second energy unit are connected in series. 
     The contact arms  1441 ,  1442  of the high voltage male blade  144  are respectively connected with the third negative terminal  116  and the second positive terminal  113 . That is, the positive electrode of the second energy unit and the negative electrode of the third energy unit are connected in series. The high voltage male blades  142 , 143  and  144  connect four energy units in series. As shown in  FIG.  4   , the electric energy storage device  100  outputs a voltage of 4*nV to the high voltage power tool through two voltage outputs  1412 ,  1452 . 
     Second Embodiment 
     As shown in  FIG.  14   , which is another embodiment of the electric energy storage device, it differs from the electric energy storage device  100  of the first embodiment in the arrangement of the conductive terminals. 
     The electric energy storage device  200  includes a housing (not shown), four energy units (also called as a first string of battery cells, a second string of battery cells, a third string of battery cells, a fourth string of battery cells) housed within the housing, and a socket  210  electrically connected to the four energy units. As shown in conjunction with  FIG.  15   , the socket  210  includes a body  206  and multiple independently arranged conductive terminals housed in the body  206 . The multiple conductive terminals may include eight electrode terminals electrically connected to positive and negative electrodes of four energy units through a circuit board. Specifically, a first positive terminal  211  and a first negative terminal may be connected to positive and negative electrodes of a first energy unit  212 , a second positive terminal  213  and a second negative terminal  214  may be connected to the positive and negative electrodes of the second energy unit, a third positive terminal  215  and a third negative terminal  216  may be connected to the positive and negative electrodes of the third energy unit, and a fourth positive terminal  217  and a fourth negative terminal  218  may be connected to the positive and negative electrodes of the fourth energy unit. The multiple conductive terminals may further include a communication terminal and a charging terminal (not shown) in addition to the eight electrode terminals. 
     In this embodiment, the eight electrode terminals may be arranged in a line, from left to right, as the fourth negative terminal  218 , the third negative terminal  216 , the second negative terminal  214 , the first negative terminal  212 , the second positive terminal  213 , the third positive terminal  215 , the fourth positive terminal  217 , and the first positive terminal  211 . The contact portion of each electrode terminal is substantially the same as the contact portion referred to in the first embodiment. 
     The electric energy storage device  200  of the disclosure is also capable of supplying energy to various power tools having different rated voltages, each power tool being provided with a plug which interfaces with the same socket  210  of the electric energy storage device  200 . The different plugging configurations may use different connection states established among the eight electrode terminals of the socket  210 . Specifically, the different connection states are formed among the four battery packs to generate different output voltages, which can be seen with reference to  FIGS.  1  to  4   . Each plug comprises a communication male blade (not shown) matched and plugged with the communication terminal, and a charging male blade (not shown) matched and plugged with the charging terminal, which is for voltage input. 
       FIG.  15    shows a situation where the conductive terminals of the socket  210  of the electric energy storage device  200  are matched with the low-voltage male blade of the low-voltage plug  220  of a low-voltage electric tool. 
     Referring to  FIG.  16   , the low-voltage plug  220  includes two independently disposed low-voltage male blades  221 , 222  mounted on an insulating base (not shown). The low-voltage male blade  221  includes four contact arms  2211 ,  2212 ,  2213 ,  2214  arranged side by side, three connection portions  2215 ,  2216 ,  2217  each connecting two of the adjacent contact arms, and a voltage output part  2218  connecting with the contact arms  2211 ,  2212 ,  2213 ,  2214 . The voltage output part  2218  is arranged on the rear side of the low-voltage male blade  221  and can be connected with one of the contact arms  2211 ,  2212 ,  2213 , 2214  lies in the same vertical plane. The low-voltage male blade  222  includes four contact arms  2221 ,  2222 ,  2223 ,  2224  arranged side by side, three connection portions  2225 ,  2226 ,  2227  each connecting two of the adjacent contact arms, and a voltage output portion  2228  connecting to the contact arms  2221 ,  2222 ,  2223 ,  2224 . The low-voltage male blade  222  may have a similar structure as the low-voltage male blade  221 . 
     Referring back to  FIG.  15   , when the socket  210  is mated with the low-voltage plug  220 , the contact arms  2211 ,  2212 ,  2213 ,  2214  of the low-voltage male blade  221  are sequentially in connection with the fourth negative terminal  218 , the third negative terminal  216 , the second negative terminal  214 , and the first negative terminal  212 . That is, the contact arms  2211 ,  2212 ,  2213 ,  2214  are connected in parallel with the negative electrodes of the four energy units. The contact arms  2221 ,  2222 ,  2223 ,  2224  of the low-voltage male blade  222  are sequentially in connection with the second positive terminal  213 , the third positive terminal  215 , the fourth positive terminal  217 , and the first positive terminal  211 . That is, contact arms  2221 ,  2222 ,  2223 ,  2224  are connected in parallel with the positive electrodes of the four energy units. Thus, two low-voltage male blades  221 , 222  are coupled in parallel to four energy units, and as shown in  FIG.  1   , the electric energy storage device  200  may outputs an nV voltage for the low-voltage power tool through two voltage outputs  2218 ,  2228 . 
       FIG.  17    shows a situation in which the conductive terminals of the socket  210  of the electric energy storage device  200  are matched with the medium voltage male blades of the medium voltage plug  230  of a medium voltage electric tool. 
     As shown in connection with  FIG.  18   , the medium voltage plug  230  includes three independently arranged medium voltage male blades  231 ,  232 ,  233  positioned side by side, with the medium voltage male blades  231 ,  232 ,  233  being mounted on a base (not shown). The medium voltage male blade  231  includes two oppositely disposed contact arms  2311 ,  2312 , a connection portion  2313  connecting the contact arms  2311 ,  2312 , and a voltage output portion  2314  connecting to the contact arms  2311 ,  2312 . The medium-voltage male blade  232  includes two oppositely arranged contact arms  2321  and  2322 , a connection portion  2323  connecting the contact arms  2321  and  2322  and a voltage output part  2324  connecting with the contact arms  2321  and  2322 . The medium-voltage male blade  233  includes four contact arms  2331 ,  2332 ,  2333 ,  2334  arranged side by side, and three connection portions  2335 ,  2336 ,  2337  each connecting two adjacent contact arms. 
     Returning to  FIG.  17   , when the socket  210  is mated with the medium voltage plug  230 , the two contact arms  2311 ,  2312  of the medium voltage male blade  231  are mated respectively with the fourth negative terminal  218  and the third negative terminal  216 . The two contact arms  2321 ,  2322  of the medium voltage male blade  232  are respectively plugged with the second positive terminal  213  and the first positive terminal  211 . The four contact arms  2331 ,  2332 ,  2333 ,  2334  of the medium voltage male blade  233  are sequentially plugged with the second negative terminal  214 , the first negative terminal  212 , the third positive terminal  215 , and the fourth positive terminal  217 . Thus, the first and second energy units are connected in parallel, and the third and fourth energy units are first connected in parallel and then connected in series with the first and second energy units (which are connected in parallel). As shown in  FIG.  2   , the electric energy storage device  200  outputs a voltage of 2*nV to the medium voltage power tool through the two voltage outputs  2314 ,  2324 . 
     It can be seen in other embodiments, the plug may be provided as a combination of other types of male blades so that when the plug is mated with the socket  210 , each two of the four energy units are connected in series and then connected in parallel therebetween to output a voltage of 2*nV, which will not be described in detail herein. 
       FIG.  19    shows a situation where the conductive terminals of the socket  210  of the electric energy storage device  200  are matched with the high-voltage male blades of the high-voltage plug  330  of a high-voltage electric tool. 
     As shown in connection with  FIG.  20   , the high voltage plug  240  includes five independently disposed high voltage male blades  241 ,  242 ,  243 ,  244 ,  245  mounted on a base (not shown). Here, the high-voltage male blade  241  includes a contact arm  2411  and a voltage output portion  2412  connected to the contact arm  2411 . The high voltage male blade  245  includes a contact arm  2451  and a voltage output  2452  connected to the contact arm  2451 . The high voltage male blade  242  includes two contact arms  2421 ,  2422  and a connection portion  2423  connecting the two contact arms  2421 ,  2422 . The high-voltage male blade  243  includes two contact arms  2431 ,  2432  and a connection portion  2433  connecting the contact arms  2431 ,  2432 . The high voltage male blade  244  includes two contact arms  2441 ,  2442  and a connection portion  2443  connecting the contact arms  2441 ,  2442 . 
     Returning to  FIG.  19   , when the socket  210  is mated with the high voltage plug  240 , the contact arm  2411  of the high voltage male blade  241  is mated with the fourth negative terminal  218 , the contact arm  2451  of the high voltage male blade  245  is mated with the first positive terminal  211 , and the contact arms  2421 ,  2422  of the high voltage male blade  242  are mated with the fourth positive terminal  217  and the third negative terminal  216  respectively, so that the third and fourth energy units are connected in series. The contact arms  2431  and  2432  of the high-voltage male blade  243  are respectively plugged with the third positive terminal  215  and the second negative terminal  214 , so that the third and second energy units are connected in series. The contact arms  2441  and  2442  of the high-voltage male blade  244  are respectively plugged with the second positive terminal  213  and the first negative terminal  212 , so that the second and first energy units are connected in series. That is, the high-voltage male blades  241 ,  242 ,  243  are connected in series with four energy units, the contact arm  2411  of the high-voltage male blade  241  is inserted into the fourth negative terminal  218 , and the contact arm  2451  of the high-voltage male blade  245  is inserted into the first positive terminal  211 . As shown in  FIG.  19   , the electric energy storage device  100  outputs a voltage of 4*nV to the high-voltage power tool through the two voltage output portions  2412 ,  2452 . 
     In summary, four energy units with substantially the same voltage are respectively matched and plugged with a low-voltage plug, a medium-voltage plug, and a high-voltage plug through electrode terminals. Specifically, the four energy units may be mutually connected in parallel to output a low voltage; each two of the four energy units may be parallel connected first and then series connected therebetween or each two of the four energy units may be series connected first and then parallel connected therebetween to output a medium voltage, or the four energy units may be mutually connected in series to output a high voltage. Therefore, the same electric energy storage device can selectively supply power to three electric tools with different rated working voltages. Such an operation is simple and convenient, and the cost is reduced. 
     Therefore, although the disclosure has been described herein with reference to specific embodiments, freedom of modification, various changes and substitutions are intended to be included in the above disclosure, and it should be understood that, in some cases, on the premise of being without departing from the scope and sprit of the proposed disclosure, some features of the disclosure will be adopted without corresponding use of other features. Therefore, many modifications can be made to adapt specific environments or materials to the essential scope and spirit of the disclosure. The disclosure is not intended to be limited to specific terms used in the following claims and/or specific embodiments disclosed as best ways to implement the disclosure, but the disclosure will include any and all embodiments and equivalents falling within the scope of the appended claims. Therefore, the scope of the disclosure will only be determined by the appended claims.