Reusable protection device for protecting a rechargeable battery, and operating method therefor

Abstract

The invention relates to a reusable protection device (V) for protecting a rechargeable battery (10) from overheating as the rechargeable battery is charged by means of a charging device (12). The reusable protection device comprises a first housing element (3), which has an electrical circuit arrangement (B) having a first electrical switch (4), and a second housing element (1), which is rotatably connected to the first housing element, the two housing elements being rotatable between a closed position and open positions. Also, a band (9) is provided which can be fastened, at one end, to the first housing element and which is guidably held in the second housing element, such that a loop (9a) in which the battery to be charged can be securely fastened is formed between the band and the battery side. Only in the closed position, the first switch is closed so that a circuit for charging the battery can be closed. The circuit can be interrupted when an actual volume of the battery exceeds a target volume of the battery, by virtue of the fact that the second housing element can be rotated by means of a torque which is caused by the battery when the battery swells as a result of the volume increase and which acts on the second housing element via the tensioned and locked band.

Description

[0001] Reusable protective device for protecting a rechargeable battery and method of operation for such a device

[0002] Field of the invention

[0003] The invention relates to a reusable protective device for protecting a rechargeable battery and an operating method for such a device according to the respective independent claim.

[0004] background

[0005] Rechargeable batteries are well known. They are available in a wide variety of different designs. Shape and size can vary greatly depending on the application. Furthermore, such batteries differ in their electrical properties, such as charging time, energy density, efficiency, etc. These properties depend on the materials used. The most common batteries include lithium-ion batteries, which can be further subdivided into, for example, lithium polymer batteries (LiPo), lithium manganese batteries (LiMn), etc.

[0006] In general, the charging process with rechargeable batteries can be problematic due to the heat generated by the energy input. This can lead to the battery cell overheating or, as in the case of LiPo batteries, to the battery cell "swelling up", for example if such a battery cell is damaged, which can happen, for example, due to overloading during discharge or due to complete discharge. In the worst case, the battery cell can explode or catch fire, which of course must be prevented at all costs to avoid potential danger to the user and destruction of the battery. For this purpose, protection solutions have been developed for various battery types. While complex computer-aided protection systems with intelligent charging cycles have been developed for larger batteries, e.g. those found in electric vehicles, these solutions cannot be used for small batteries, such as those found in mobile phones.typically found in remote-controlled model airplanes, because they would be too big, too heavy and too expensive.

[0007] Solutions have also been developed for such "small format" applications. For example, there are devices for LiPo batteries that interrupt the charging current when the battery swells. This is achieved by a metal band tearing as the volume increases, thereby interrupting the circuit. This solution has the disadvantage that the protective device can only be used once. Other solutions, particularly for model vehicles where weight is not a major factor, use a hard-case battery where swelling is less of a problem. Using fewer battery cells can also be less of a problem, for example in applications for children.

[0008] Description of the invention

[0009] The object of the invention is to provide an improved protective device, in particular a reusable protective device.

[0010] The object is achieved in a first aspect of the invention with a reusable protective device for protecting a rechargeable battery from overheating during charging by means of a charger. The protective device has electrical connections so that one pole of the battery and the same pole of the charger can be connected to the protective device. It further comprises a first housing element with an electrical circuit which has a first electrical switch, and a second housing element which is rotatably connected to the first housing element by means of a first rotary joint arranged on a battery side of the first housing element. The two housing elements are rotatable between a closed position in which they rest against one another and open positions. The housing elements can be held in the closed position by means of a retaining force caused by a retaining device.Finally, the protective device comprises a strap which, on the one hand, can be fastened at one end to the first housing element and, on the other hand, is guided in the second housing element such that a loop is formed between the strap and the battery side, in which loop the battery to be charged can be received. The strap can be tensioned and locked in the second housing element so that the battery is firmly fixed to the battery side of the first housing element.

[0011] The first switch is open in the rest position and closed only in the closed position. Closing the first switch electrically connects the charger terminal to the same terminal on the battery, thus creating an electrical circuit for charging the battery when the battery is properly connected to the charger.

[0012] The circuit can be interrupted if, during ongoing charging of the fixed battery, an actual volume of the battery exceeds a target volume of the battery, in that the second housing element can be rotated about the first rotary joint by means of a torque caused by the battery expanding due to the increase in volume and acting on the second housing element via the tensioned and locked band, overcoming the retaining force, as a result of which the housing elements can be transferred from the closed position to one of the open positions and the first switch can be opened in the process. The object is achieved in a second aspect of the invention, which is an alternative to the first aspect of the invention, with a reusable protective device for protecting a rechargeable battery from overheating during charging by means of a charger.The protective device has electrical connections so that one pole of the battery and the same pole of the charger can be connected to the protective device. It further comprises a first housing element with an electrical circuit which has a first electrical switch and an interrupter circuit connected in series with the switch. It further comprises a second housing element which is rotatably connected to the first housing element by means of a first rotary joint arranged on a battery side of the first housing element. The two housing elements are rotatable between a closed position in which they rest against one another and open positions. The housing elements can be held in the closed position by means of a retaining force provided by a retaining device.Finally, the protective device comprises a strap, one end of which can be fastened to the first housing element and the other end of which is guided in the second housing element, such that a loop is formed between the strap and the battery side, in which loop the battery to be charged can be received. The strap can be tensioned and locked in the second housing element, so that the battery is firmly fixed to the battery side of the first housing element.

[0013] The first switch is open in the rest position and closed only when the housing elements are closed. The breaker circuit is conductive in the rest position, regardless of the position of the housing elements, so that when the first switch is closed and the breaker circuit is conductive, the charger terminal can be electrically connected to the same battery terminal. This creates an electrical circuit for charging the battery when the battery is connected to the charger as intended.

[0014] The circuit can be interrupted if, while the fixed battery is being charged: a target volume of the battery is exceeded by an actual volume of the battery, in that the second housing element can be rotated about the first rotary joint by means of a torque caused by the battery expanding due to the increase in volume and acting on the second housing element via the tensioned and locked band, overcoming the retaining force, whereby the housing elements can be moved from the closed position to one of the open positions and the switch can be opened to interrupt the circuit, and / or a maximum permissible temperature of the battery is exceeded during charging, and the circuit can therefore be interrupted by means of the interrupter circuit.

[0015] A third aspect of the invention relates to a method for protecting a rechargeable battery from overheating when being charged by means of a charger, by means of a protection device according to the first or second aspect of the invention. The method comprises the following steps: a) connecting one pole of the battery to a first electrical terminal of the protection device and the same pole of the charger to a second terminal of the protection device, b) inserting the battery into the loop, c) tensioning the band to bring the housing elements into the closed position by pulling the band away from the second housing element and towards the first housing element, so that the battery is firmly fixed to the battery side of the first housing element, d) locking the band when the housing elements are in the closed position, and e) connecting the other pole of the battery directly to the same other pole of the charger.

[0016] The invention has the advantage of generally providing a reusable solution for protecting rechargeable batteries. This is achieved in the first variant of the device by interrupting the charging circuit by rotating the housing elements to an open position when the battery swells, which can occur particularly with LiPo batteries due to overheating. This makes it possible to simply return the device to the closed position of the housing elements the next time it is used. No repair is necessary.

[0017] A further advantage is that, due to the special design of the device with a loop that can be adjusted to the size of the battery in order to tightly enclose it, different sizes of batteries are possible.

[0018] The second variant of the device according to the invention has the aforementioned advantage over the first option. In addition, the second option offers the advantage that protection against overheating can be provided directly by temperature monitoring, so that even types of batteries that do not swell upon overheating can be protected. Combining the first and second options, the protective device thus accommodates a wide range of battery types.

[0019] The process shows that the device can be ready for use in just a few steps and with little effort by essentially only clamping the battery in the loop and closing the housing parts.

[0020] Brief description of the drawings Further embodiments, advantages, and applications of the invention will become apparent from the dependent claims and from the following description with reference to the figures. In the drawings:

[0021] Fig. 1 is a side view of an arrangement for charging a battery with a protective device according to the invention in a first open intermediate position,

[0022] Fig. 2 is a side view of the arrangement for charging a battery with a protective device according to the invention in a closed position,

[0023] Fig. 3 is a side view of the arrangement for charging a battery with a protective device according to the invention in a second open position,

[0024] Fig. 4 is a side view of a first housing element of the protective device of Fig. 1,

[0025] Fig. 5 and 6 each show a side view of components of detail A from Fig. 1, and

[0026] Fig. 7 is a side view of a second housing element of the protective device from Fig. 1.

[0027] Ways to implement the invention

[0028] For the sake of simplicity, a rechargeable battery is referred to throughout the text as a rechargeable battery or rechargeable cell or similar.

[0029] Fig. 1 shows an arrangement for charging a battery 10 with a protective device V according to the invention. The arrangement further comprises a charger 12. The charger 12 is electrically connected to the negative pole of the battery 10 by means of the negative pole.

[0030] The protective device V comprises a first housing part 3 and a second housing part 1 which are rotatably connected to one another by means of a first pivot joint 1a (Figs. 4, 7). In this figure, the battery to be charged has not yet been inserted and the first and second housing parts are in a first open position, which is also referred to as the intermediate position. In this state, the battery cannot be charged.

[0031] The figure also shows two detailed views A and B, which are described in detail later. Detailed view A shows components of the second housing element 1, and detailed view B shows components of the electrical circuit for charging / discharging the battery.

[0032] Fig. 2 shows the protective device from Fig. 1, but with the battery inserted. Here, the first and second housing parts are in a closed position, allowing charging of the battery.

[0033] Fig. 3 shows the protective device from Fig. 1 in the event of a fault in which the battery is swollen and the protective device is acting to disconnect the electrical charging circuit, hereinafter also referred to as the circuit. When the electrical charging is interrupted, the two housing elements move from the closed position, in which they rest against each other, to an open position.

[0034] The individual elements of Figures 1-3 will now be described in detail with the aid of Figures 4-7. First, the components themselves are described, followed by any interactions with other components.

[0035] Fig. 4 shows a carrier body 1 of the second housing element, which is fastened to the first housing element 3 by means of the first rotary joint. A first side 1c of the carrier body rests against a first side 3b (Fig. 7) of the first housing element in the closed position and does not rest against the first side of the first housing element in any of the open positions. In this context, it is noted that due to the rotation about the first rotary joint 1a, a plurality of open positions is possible, depending on how far the housing elements are rotated about the first rotary joint. Therefore, the plural form of open positions is referred to throughout the document.

[0036] The carrier body 1 of the second housing element comprises a locking pin 7, which projects from the first side 1c so far that in the closed position its free end comes to lie in a recess 5a (Fig. 3) in the first housing element.

[0037] Fig. 5 shows a strap guide element 2 rotatably mounted in or on the support body 1 of the second housing element by means of a second pivot joint 1b. The support body preferably comprises lateral ears in which a hinge joint is held as a second pivot joint. A first side of the strap guide element 2 faces the first side of the first housing element (see, for example, Fig. 1) and is formed from a first surface section 2a and a second surface section 2b. The two surface sections do not lie in the same plane.

[0038] Furthermore, a first magnet 6.1 of a retaining device is shown.

[0039] Fig. 6 shows a clamping lever 8 of the second housing element, which is rotatably mounted in the band guide element 2 by means of a third pivot joint 1c and serves to lock the band 9 (Fig. 1-3). The clamping lever comprises a second magnet 6.2, which is arranged such that the second magnet of the clamping lever 8 and the first magnet 6.1 of the band guide element attract each other.

[0040] In summary, the tape guide element 2 is rotatably mounted in the carrier body 1, and the clamping lever 8 is rotatably mounted in the tape guide element 2. These two rotary movements can be performed independently of one another, which is illustrated by the two independent rotary joints 1b and 1c. However, it is preferred if a single rotary joint is used, which is also designed as a hinge, which reduces complexity and material requirements. In this case, the tape guide element is held between the ears of the carrier body, and the clamping lever is held between further ears of the tape guide element.

[0041] Fig. 7 shows the first housing element 3. As mentioned, this is designed such that it is connected to the second housing element by means of the first rotary joint 1a. It has the first side 3b mentioned in the context of Fig. 4 and a further battery side 3a. Furthermore, a further first magnet 6 is provided on the first side 3b. The circuit from detail B of Fig. 1 is shown inside the first housing part and is responsible for establishing or interrupting the electrical circuit necessary for charging the battery.

[0042] The circuit comprises a switch (microswitch) 4. When the switch 4 is closed, it connects a positive pole of the charger 12, which charger is electrically connected to the device by means of a first charging cable 11a, to the battery to be charged. The device is in turn connected to the positive pole of the battery by means of a second charging cable 11b. As already mentioned, the negative poles of the charger and the battery are directly connected by means of a third charging cable 11c. If the switch 4 is open, no current can flow and the charging process is interrupted. An overcurrent protection device 13 is also provided in the circuit. Finally, the circuit has a button 5 which can be actuated by a user of the protective device. The button 5 is designed such that it is in contact with the switch 4 and can bring it into the closed position.

[0043] The circuit also includes an interrupter circuit 14, which is to be described later and is preferably designed as a bimetallic switch. The functioning of the protective device V will be explained below using the components already described.

[0044] First, the fixing of the battery will be explained. In Fig. 1, the battery is shown outside the loop formed by the band 9. In this configuration, the battery cannot be charged because the switch 4 is open. This is intended to prevent the battery from being charged while bypassing the protective function. Fig. 2 shows the battery clamped in the loop and being charged (switch 4 closed). For this purpose, the battery was inserted into the loop and the band was tightened at the free end 9a (Fig. 1) by pulling it essentially to the right in the figure while the clamping lever 8 is pressed and released after tightening. Tightening the band causes the second housing element 1 to rotate towards the first housing element and tends to assume the closed position because pulling on the free end of the band creates a torque related to the first pivot joint 1a.In this state, the housing parts are in the open intermediate position and the clamping lever abuts against the button 5. To assume the closed position, the button 5, the function and design of which will be explained later, simply has to be pressed. This causes the housing parts to jump into the closed position because the magnets 6 and 6.1 attract each other. However, it is also possible to pull the band 9 at the same time. This brings the housing elements into the closed position in which the battery is firmly fixed in the loop. "Firmly" in the context of the document means that the battery has essentially no play and is firmly fastened in the loop by being pressed against the aforementioned battery side 3a (also called the pivot side) of the first housing element (Fig. 7).The protective device is preferably designed such that the fixing (tightening) of the battery can only be carried out when the housing elements are in the closed position. This ensures that when the protective device is used as intended, the battery can only be charged when it is also firmly tensioned. Of course, the protective device is designed such that at least one charging cable 11a, 11b, 11c for closing the circuit for charging the battery can only be connected after the battery has been locked / fixed in the closed position of the housing elements. For example, the charging cable 11b can be provided with a pin which is plugged into the device, which is illustrated by the circle at the end of the charging cable in Fig. 1. When the housing elements are in the closed position, the band is locked in the band guide element by means of the clamping lever.

[0045] Now we will explain how to remove the battery or interrupt the charging process due to an error.

[0046] As stated, the circuit is broken when the housing elements are moved from the closed position to an open position, which can be intentional when the battery is fully charged, or can happen automatically in the event of a fault. The user can bring about this simply by pulling the second housing element away from the first housing element. It is preferred that rotation of the second housing element from the closed position to an immediately subsequent open position causes the band to loosen slightly, i.e. the loop to enlarge, in order to facilitate the intended removal of the charged battery, since the user can then grip the loop and loosen it further. With reference to Fig.5 the band can therefore be guided in the band guide element 2 in such a way that a rotation of the band guide element such that the first surface section 2a is aligned parallel to the first side 3b of the first housing element corresponds to an enlargement of the loop, and a rotation of the band guide element such that the second surface section 2b is aligned parallel to the first side of the first housing element corresponds to a reduction in the loop.

[0047] In the event of a fault, expansion of the battery (Fig. 3) causes a fault torque related to the first pivot joint, since the band is simultaneously locked in the band guide element by the clamping lever. This causes the second housing element to rotate away from the first housing element, which in turn leads to an interruption of the electrical circuit.

[0048] Now we will explain how the housing elements are preferably held permanently in the closed position.

[0049] Fixing the battery so that it is pressed firmly against the battery side of the first housing element tensions the band and thus creates a permanent torque against the first pivot joint. This torque would cause the second housing element to be pulled away from the first housing element, as explained above for the event of a fault. When the protective device is in operation, a greater retention force / greater counter torque to this permanent torque must be provided in order to hold the housing elements in the closed position. They are intended to only move into an open position if either the user overcomes this retention force / counter torque using their own strength, or to be more precise, the difference between the permanent torque and the retention force / counter torque, or the fault torque caused by the inflation of the battery overcomes this difference in the event of a fault.This retaining force is generated by means of a retaining device comprising the two first magnets 6, 6.1. In the embodiment shown, the first housing element on the first side and the band guide element on the second section each have one of the two first magnets. The first magnets are arranged such that they attract one another and thereby provide the retaining force.

[0050] Now we will explain how the magnets interact in different positions of the housing elements to provide different functions.

[0051] By rotating the tape guide element 2 relative to the carrier body 1, either the first 2a or the second surface section 2b can be aligned parallel to the first side 3b of the first housing element.

[0052] When the first surface section is aligned parallel, it is in the same plane as the first side of the carrier body. Only in the closed position does the first side of the carrier body, together with the first surface section of the band guide element, rest against the first side of the first housing element, as can be seen in Fig. 2. It can be seen from the figure that the magnet 6. 1 is not parallel to the magnet 6. This position of the first magnets relative to one another defines the retaining force when the housing elements are in the closed position. However, it does not correspond to a maximum attractive force of the magnets. This is also not necessary since, as explained above, only a differential force is required to open the housing elements.In this embodiment, the percentage by which the actual volume of the battery may exceed the target volume until the circuit can be interrupted by moving the housing parts from the closed position to one of the open positions while the battery is being charged can be adjusted depending on the strength of the first magnets. In other words, by appropriately selecting the first magnets, the time at which the protective function is triggered can be adjusted in the event of a fault as the battery continues to expand.

[0053] When the second surface section 2b is aligned parallel, it projects beyond the plane of the first side of the carrier element in the direction of the first side of the first housing element and, in an open intermediate position, rests against the first side of the first housing element as a spacer to the first side of the carrier element, so that the closed position of the housing elements cannot be assumed. This is visible in Fig. 1: the carrier body 1 does not rest against the surface 3b (Fig. 7) of the first housing element. In the open intermediate position, the first magnets are arranged parallel to one another and provide the aforementioned maximum attractive force. This is advantageous when considering the case shown in Fig. 1, in which the battery is not inserted in the loop, in order to prevent the closed position of the housing elements from being assumed and the protective effect of the device being circumvented.Obviously, charging the battery outside the loop could lead to excessive inflation, overheating, and fire or explosion. In other words, this arrangement of the first magnets and the corresponding contact surfaces 2b and 3b represents a safety feature. In the figures, the designations N and S in the magnets represent the poles of the respective magnets.

[0054] A further magnet 6.2 is provided in the clamping lever. It is arranged in such a way that it attracts the first magnet 6.1. Detailed view A in Figure 1 shows an arrangement of the clamping lever 8 relative to the strap guide element 2, with the clamping lever being pressed by the user. This allows the strap 9 to be easily pulled through the strap guide element to reduce the loop and secure the battery in the loop. If the clamping lever is released by the user, the force of attraction between the first magnet 6.1 and the second magnet 6.2 causes it to spring into the position shown in Figure 1 and clamp the strap. This makes operation easier for the user. The closing and opening of the circuit using the button 5 mentioned above is described below, with reference to the movement of the housing elements relative to one another.

[0055] As mentioned, the first housing element comprises the button 5 which can be actuated by the user of the protective device. The detailed view B in each of Figures 1, 2 and 3 shows the respective position of the button in interaction with the aforementioned locking pin 7 (Fig. 4). In the rest position the button is not pressed, which means that it does not act on the switch 4 and the switch is open. This is preferably achieved by providing a spring which is relaxed when the button is not pressed and tensioned when the button is pressed. The non-pressed position of the button corresponds to the view in Fig. 1. It is also visible that the locking pin does not reach the button, which is prevented by the aforementioned spacer function of the second partial surface 2b of the second housing element. The housing elements can only be moved into the closed position when the button is pressed. Fig.It is also evident from Fig. 1 that even if the user were to pull on the strap 9 so hard that the corresponding torque would theoretically cause the support body to rotate into the position in which the first partial surface 2a would rest against the first housing element, this would not be possible due to the stop of the locking pin on the button. Thus, assuming the closed position in the configuration shown in Fig. 1 is impossible.

[0056] Fig. 1 also shows the recess 5a, which is formed by the head of the key 5 being smaller in diameter than the key body. The recess is only accessible to the locking pin when the key is in the pressed position, as can be seen in Fig. 2. The recess is preferably arranged such that the key can be locked in the pressed position. This is achieved by pulling the second housing element with the carrier body towards the first housing element when the key is pressed, allowing the free end of the locking pin to penetrate the recess. If the free end of the locking pin remains in this position, the pin cannot return to its rest position under the permanent action of the spring, as can be seen in detail B in Fig. 2.The pressed button can be permanently locked, preferably during the battery charging process. It can only be released in the event of an increase in battery volume or due to user intervention when moving the housing elements from the closed position to one of the open positions, thus returning it to the rest position.

[0057] The protective device according to the invention can be manufactured in various sizes, wherein the length L (Fig. 2) of the device is preferably decisive for the maximum extension in this direction of a largest battery that can be used with the respective device. For the best possible protective effect, it is preferred if either the length or the width of the largest battery that can be used with a specific protective device does not exceed the length L or only slightly, preferably between 5% and 10%. The battery is then clamped in the loop with this smaller dimension (length or width).

[0058] According to the second variant of the protective device according to the invention, the circuit from detail B has an interrupter circuit 14, which is preferably designed as a bimetallic switch. This advantageously also ensures protection for non-expanding batteries, which merely heat up in the event of a fault, if the interrupter circuit is used in combination with the protective circuit for expanding batteries described above. However, it can also be used on its own as an alternative. The preferred bimetallic switch is preferably arranged directly on the battery side of the first housing element, so that its protective effect can develop as quickly as possible when the temperature of the battery increases. It is designed such that it interrupts the circuit when a fixed limit temperature is reached. The functional principle of a bimetallic switch is known and will not be explained in more detail here.

[0059] Alternatively, the interrupter circuit can be an electronic circuit that electronically interrupts the circuit when a programmable temperature limit is reached. Especially if the interrupter circuit is programmable, the protective device can be advantageously adapted to different battery types.

[0060] The method for operating the protective device according to the invention will now be summarized , the steps of which have already been indirectly described .

[0061] In a first step, one pole of the battery is connected to a first electrical terminal of the protection device and the same pole of the charger is connected to a second terminal of the protection device, e.g. the positive pole, in the example shown.

[0062] The battery is then inserted into the loop and the band is tensioned to bring the housing elements into the closed position by pulling the free end of the band away from the second housing element and towards the first housing element so that the battery is firmly fixed to the battery side of the first housing element.

[0063] Finally, the other terminal (here, the negative terminal) of the battery is connected directly to the same other terminal of the charger. This step and the first step can be interchanged.

[0064] As described in the illustrated embodiment, a preferred but optional step may consist of holding the button down during battery charging until the housing elements are moved into the closed position. The button is then locked and can be released. However, other arrangements for closing and opening the circuit may also be used, particularly in which the closing of the circuit occurs independently of moving the housing elements into the closed position and only the interruption of the circuit is coupled to the rotational movement for moving the housing elements into an open position.

[0065] It is noted that the protective device according to the invention can be used not only when charging a battery but also when discharging a battery.

[0066] Although preferred embodiments of the invention have been described, it is to be understood that the invention may be practiced in other ways within the scope of the following claims. Terms used in the description such as "preferred," "particularly," "advantageous," etc., refer only to optional and exemplary embodiments.

Claims

Patent claims 1. Reusable protective device (V) for protecting a rechargeable battery (10) from overheating during charging by means of a charger (12), wherein the protective device has electrical connections (10a) so that a pole of the battery and the same pole of the charger can be connected to the protective device, further comprising - a first housing element ( 3 ) with an electrical circuit (B ) which has a first electrical switch ( 4 ), - a second housing element (1) which is rotatably connected to the first housing element by means of a first rotary joint (1a) arranged on a battery side (3a) of the first housing element, wherein the two housing elements are rotatable between a closed position in which they abut one another and open positions, wherein the housing elements are held in the closed position by means of a retaining force caused by a retaining device, - a band ( 9 ) , which can be fastened at one end to the first housing element and at the other end is guided in the second housing element in such a way that a loop ( 9a ) is formed between the band and the battery side , in which loop the battery to be charged can be received , wherein the band can be tensioned and locked in the second housing element so that the battery is firmly fixed to the battery side of the first housing element , wherein the first switch is open in the rest position and closed exclusively in the closed position , wherein by closing the first switch the pole of the charger can be electrically connected to the same pole of the battery so that when the battery is connected to the charger as intended , an electrical circuit for charging the battery can be closed , The circuit is interruptible if, during charging of the fixed Battery an actual volume of the battery exceeds a target volume of the battery, in that the second housing element can be rotated about the first rotary joint by means of a torque caused by the battery expanding due to the increase in volume and acting on the second housing element via the tensioned and locked band, overcoming the retaining force, whereby the housing elements can be transferred from the closed position into one of the open positions and the first switch can be opened.

2. Reusable protective device for protecting a rechargeable battery from overheating during charging by means of a charger, wherein the protective device has electrical connections so that a pole of the battery and the same pole of the charger can be connected to the protective device, further comprising - a first housing element with an electrical circuit which has a first electrical switch ( 4 ) and an interrupter circuit ( 14 ) connected in series with the first switch, - a second housing element which is rotatably connected to the first housing element by means of a first rotary joint arranged on a battery side of the first housing element, wherein the two housing elements are rotatable between a closed position in which they abut one another and open positions, wherein the housing elements are held in the closed position by means of a retaining force caused by a retaining device, - a band which can be fastened at one end to the first housing element and which can be guided in the second housing element in such a way that a loop is formed between the band and the battery side, in which loop the battery to be charged can be received, wherein the band can be tensioned and locked in the second housing element, so that the battery is firmly fixed to the battery side of the first housing element, wherein the first switch is open in the rest position and closed exclusively in the closed position of the housing elements and wherein the interrupter circuit is current-conducting in the rest position regardless of the position of the housing elements, so that when the first switch is closed and the interrupter circuit is current-conducting, the pole of the charger can be electrically connected to the same pole of the battery, so that when the battery is connected to the charger as intended, an electrical circuit for charging the battery can be closed,wherein the circuit is interruptible if, during ongoing charging of the fixed battery: a target volume of the battery is exceeded by an actual volume of the battery, in that the second housing element can be rotated about the first pivot joint by means of a torque caused by the battery expanding due to the increase in volume and acting on the second housing element via the tensioned and locked band, overcoming the retaining force, whereby the housing elements can be moved from the closed position to one of the open positions and the switch can be opened to interrupt the circuit, and / or a maximum permissible temperature of the battery is exceeded during charging, and the circuit can therefore be interrupted by means of the interrupter circuit. 3 . Protection device according to claim 2 , wherein the interrupter circuit is a bimetallic switch which is arranged directly on the battery side of the first housing element and is designed in such a way that it interrupts the circuit when a fixed limit temperature is reached , or wherein the interrupter circuit is an electronic circuit which interrupts the circuit when a programmable limit temperature is reached .

4. Protection device according to one of the preceding claims, wherein the second housing element comprises a carrier body (1) which is fastened to the first housing element by means of the first rotary joint, wherein a first side (1c) of the carrier body abuts a first side (3b) of the first housing element in the closed position and does not abut the first side of the first housing element in any of the open positions. 5 . Protection device according to claim 4 , wherein the second housing element comprises a band guide element ( 2 ) rotatably mounted in the carrier body relative to the latter, wherein a first side of the band guide element (2) faces the first side of the first housing element and is formed from a first surface section (2a) and a second surface section (2b), wherein the two surface sections do not lie in the same plane, wherein by rotating the band guide element relative to the carrier body either the first or the second surface section can be aligned parallel to the first side of the first housing element, wherein when the first surface section is aligned parallel, it is in the same plane as the first side of the carrier body and exclusively in the closed position the first side of the carrier body together with the first surface section of the band guide element rests against the first side of the first housing element, wherein, when the second surface section is aligned parallel, it projects beyond the plane of the first side of the carrier element in the direction of the first side of the first housing element and, in an open intermediate position, rests against the first side of the first housing element as a spacer to the first side of the carrier element, so that the closed position of the housing elements cannot be assumed.

6. A protective device according to claim 5, wherein the retaining device comprises two first magnets (6, 6.1), wherein the first housing element on the first side and the band guide element on the second section each have one of the two first magnets, wherein the first magnets are arranged such that they attract each other, wherein in the open intermediate position the first magnets are arranged in parallel and provide a maximum attractive force, and in the closed position are arranged non-parallel and provide the retaining force which is less than the maximum attractive force.

7. Protective device according to claim 5 or 6, wherein the band can be guided in the band guide element in such a way that a rotation of the band guide element such that the first surface section is aligned parallel to the first side of the first housing element corresponds to an enlargement of the loop, and a rotation of the band guide element such that the second surface section is aligned parallel to the first side of the first housing element corresponds to a reduction of the loop.

8. Protective device according to claim 7, wherein the protective device is designed such that the fixing of the battery can be carried out exclusively in the closed position of the housing elements.

9. A protective device according to any one of the preceding claims, wherein the first housing element comprises a button operable by a user of the protective device (5), wherein the button is not pressed in the rest position, wherein the housing elements can only be moved into the closed position when the button is pressed.

10. Protection device according to claim 9, wherein the pressed button can be permanently locked during the intended charging of the battery and can be released only in the event of an increase in volume of the battery when the housing elements are transferred from the closed position to one of the open positions, so that it reaches the rest position.

11. Protection device according to claim 10, wherein the carrier body of the second housing element comprises a locking pin (7) which projects from the first side so far that in the closed position its free end comes to lie in a recess (5a) in the first housing element, wherein the recess for the locking pin is only accessible when the button is in the pressed button position, and wherein the recess is arranged such that the button can be locked in the pressed button position.

12. Protection device according to one of the preceding claims, wherein the second housing element further comprises a clamping lever (8) rotatably mounted in the band guide element relative to the latter for locking the band.

13. Protection device according to claim 12 and 6, wherein the clamping lever comprises a second magnet (6.2) arranged such that the second magnet and the first magnet of the tape guide element attract each other.

14. Protection device according to one of the preceding claims and claim 6, wherein a percentage by which the actual volume of the battery may exceed the desired volume until the circuit can be interrupted during ongoing charging of the battery by transferring the housing parts from the closed position to one of the open positions is adjustable depending on the strength of the first magnets.

15. Method for protecting a rechargeable battery from overheating when being charged by means of a charger, by means of a protection device according to one of the preceding claims, comprising the following steps: a) connecting one pole of the battery to a first electrical terminal of the protection device and the same pole of the charger to a second terminal of the protection device, b) inserting the battery into the loop, c) tensioning the band to bring the housing elements into the closed position by pulling the band away from the second housing element and towards the first housing element, at the same time so that the battery is firmly fixed to the battery side of the first housing element, d) locking the band when the housing elements are in the closed position, and e) connecting the other pole of the battery directly to the same other pole of the charger. 16 . Method according to claim 15 and claim 7 , wherein after step c ) or during step c ) an intermediate step is carried out : cl ) pressing the button and keeping the button pressed until the housing elements are in the closed position .

17. Use of the protective device according to one of claims 1 to 14 for protection during charging of lithium polymer batteries.

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