A device for protecting a circuit during activation of a reserve battery and a method for protecting a circuit during activation of a reserve battery comprised in a device

Abstract

A device (100) for protecting a circuit during activation of a reserve battery (110), wherein the device (100) comprises: a reserve battery (110) which is inactive until activation, wherein the reserve battery (110) is configured to power a load (204); and a sensor (120) configured to determining (320) if the potential over the terminals (110a) of the reserve battery (110) fulfils a predetermined criterion; and a control unit (130) configured to electrically connect (330) the reserve battery (110) to the load (204) when the predetermined criterion is fulfilled. The disclosure further relates to a method (300) for protecting a circuit during activation of a reserve battery (110) comprised in a device (100).

Description

[0001] A DEVICE FOR PROTECTING A CIRCUIT DURING ACTIVATION OF A RESERVE BATTERY AND A

[0002] METHOD FOR PROTECTING A CIRCUIT DURING ACTIVATION OF A RESERVE BATTERY COMPRISED IN A DEVICE

[0003] Technical field

[0004] The present disclosure relates to a device for protecting a circuit during activation of a

[0005] 5 reserve battery and a method for protecting a circuit during activation of a reserve battery comprised in a device. More specifically, the disclosure relates to a device for protecting a circuit during activation of a reserve battery and a method for protecting a circuit during activation of a reserve battery comprised in a device as defined in the introductory parts of the independent claims.

[0006] Background art

[0007] Many explosive devices, e.g., missiles, projectile and bomb fuses, and various weapon systems, use a battery. An example of a popular type of battery for above mention devices is a reserve battery (aka stand-by battery). A reserve battery is a primary battery where at least one part of the battery is isolated until the battery needs to be used. In the situation when5 long storage is required, reserve batteries are used, since the active chemicals of the cell are separated until needed, thus reducing self-discharge.

[0008] A reserve battery should not be mistaken for a backup battery, since a reserve battery is inert until it is activated, while a backup battery is already functional, even if it is not delivering current.

[0009] A reserve battery can be activated in a numerous of ways, e.g., by adding electrolyte, which has been kept separated from the battery cells. The electrolyte can be stored in a capsule within the reserve battery and the electrolyte is released by mechanical means.

[0010] A problem with the solutions of the prior art is that batteries kept at low charge levels for extended periods can develop higher internal resistance. Increased resistance can limit the5 battery's ability to deliver power in a fast manner, potentially causing voltage sags and affecting device performance. This scenario may occur when the temperature surrounding the electrolyte is low and thereby affecting the temperature of the electrolyte itself, which will increase the time it takes to distribute the electrolyte into the battery cell.

[0011] There is thus a need for an improved activation procedure for a reserve battery. Summary

[0012] It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above mentioned problem.

[0013] According to a first aspect there is provided a device for protecting a circuit during activation of a reserve battery, wherein the device comprises: a reserve battery which is inactive until activation, wherein the reserve battery is configured to power a load; and a sensor configured to determining if the potential over the terminals of the reserve battery fulfils a predetermined criterion; and a control unit configured to electrically connect the reserve battery to the load when the predetermined criterion is fulfilled.

[0014] An advantage of the device as described above is that the reserve battery is electrically connected to the load only when the predetermined criterion is met. This secure that the charge in the reserve battery has reached a certain level enough to power the load. Further, it also secures that the circuit of the device has a reduced risk of develop internal resistance during the activation phase of the reserve battery.

[0015] In an example embodiment, the criterion is that the electric potential over the reserve battery terminals is 1500 mv.

[0016] According to some embodiments, the reserve battery comprises: a cell stack; and an ampoule comprising electrolyte, wherein the ampoule is configured to break upon experiencing an acceleration above a predetermined threshold in at least one predetermined direction; and wherein the reserve battery is configured to, upon the ampoule breaking, guide the electrolyte into the cell stack, thereby forming a closed circuit for at least part of the reserve battery thereby activating the reserve battery.

[0017] According to some embodiments, the reserve battery comprises a damping element in which the ampoule is arranged.

[0018] According to some embodiments, the ampoule is a glass ampoule.

[0019] According to some embodiments, the sensor is a low-power sensor configured to not affect the potential over the reserve battery such that the reserve battery can reach the potential over the terminals of the reserve battery in order to fulfil the predetermined criterion without being affecting by the power needed by the low-power sensor. An advantage of the low-power sensor is that the power needed to supply the sensor is not significantly affecting the activation phase, i.e., the increasing charge of the reserve battery during the activation phase will not be significantly affected. In other words, the time it takes to charge the reserve battery to a certain potential will not be affected by the power consumed by the low-power sensor.

[0020] According to some embodiments, comprises a switch which is operatively connected to the control unit, and the switch is configured to electrically connect the reserve battery to the load when the predetermined criterion is fulfilled.

[0021] An advantage of the switch is that reserve battery cannot be electrically connected to the load until the switch has been closed, which only will occur when the predetermined criterion has been fulfilled. In an example embodiment, the control unit triggers the switch by mechanical means. In another example embodiment, the control unit triggers the switch by electrical means.

[0022] According to some embodiments, the switch is configured to, when the predetermined criterion is fulfilled, move from an initially open state to a closed state, wherein the closed state electrically connects the reserve battery to the load.

[0023] According to some embodiments, the device further comprises a timer.

[0024] In an example embodiment, the timer starts when the predetermined criterion is fulfilled. For example, when the potential reaches 1500 mV the reserve battery is connected to the load after a predetermined time e.g., 10 ms. In another example embodiment, the timer starts when the activation phase begin. In any scenario, the use of a timer is advantageously since the timer can be set to further secure that the reserve battery is not connected to the load until the predetermined criterion is fulfilled, and / or until the device has been transported to a safe distance corresponding to the time set by the timer. Put differently, since the viscosity of the electrolyte is temperature dependent, the time it will take for the electrolyte to be distributed within the cell may varies. The timer may be set to a predetermined time, e.g., 10 ms, which is long enough to secure that the reserve battery has obtained a predetermined charge. The reserve battery will not be connected to the load until the predetermined time has ended, even though the reserve battery has reached a predetermined charge sufficient to power the load. This reduces the risk of the load to be connected to the reserve battery before said reserve battery has reached a predetermined charge sufficient to power the load. In an example embodiment, the sensor configured to determining if the potential over the terminals of the reserve battery fulfils a predetermined criterion, is based in solely on a predetermined time controlled by a timer. In other words, the use of a timer replaces the other need for measuring the charge of the reserve battery. The predetermine time is configured to be long enough such that the charge of the reserve battery is determined to be sufficiently to power the load.

[0025] In an example embodiment, the load comprises an explosive charge.

[0026] According to a second aspect there is provided an arrangement for protecting a circuit of an explosive device during activation of a reserve battery comprised in a device according to the first aspect. The arrangement for an explosive device comprises: a load comprising an explosive charge; and the device according to the first aspects.

[0027] In another example embodiment, the load is connected to an explosive charge, i.e., the load and the explosive charge is two operatively connected external entities.

[0028] According to a third aspect there is provided a method for protecting a circuit during activation of a reserve battery comprised in a device according to the first aspect.

[0029] The method comprises the following steps: activating the reserve battery; determining if the potential over the terminals of the reserve battery fulfils a predetermined criterion and / or determining if a predetermined time has elapsed since the reserve battery was activated; electrically connecting the reserve battery to a load, if the criterion is fulfilled and / or if a predetermined time has elapsed since the reserve battery was activated.

[0030] In one embodiment, the reserve battery is electrically connecting to a load when the potential over the terminals of the reserve battery fulfils a predetermined criterion.

[0031] In one embodiment, the reserve battery is electrically connecting to a load when a predetermined time, controlled by a timer, has elapsed since the reserve battery was activated. The predetermined time may be set on basis on knowledge of the viscosity and / or the temperature of the environment of the reserve battery.

[0032] According to some embodiments, where in the step of activating the reserve battery comprises: breaking the ampoule the method comprises electrolyte; and distributing the electrolyte into a cell stack comprised in the reserve battery. According to some embodiments, the method further comprises a step of accelerating the device, which precedes the step of activating the reserve battery.

[0033] Effects and features of the second aspect and the third aspect are to a large extent analogous to those described above in connection with the first aspect. Embodiments mentioned in relation to the first aspect are largely compatible with the second aspect and the third aspect.

[0034] The present disclosure will become apparent from the detailed description given below. The detailed description and specific examples disclose preferred embodiments of the disclosure by way of illustration only. Those skilled in the art understand from guidance in the detailed description that changes and modifications may be made within the scope of the disclosure.

[0035] Hence, it is to be understood that the herein disclosed disclosure is not limited to the particular component parts of the device described or steps of the methods described since such device and method may vary. It is also to be understood that the terminology used herein is for purpose of describing particular embodiments only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context explicitly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may include several devices, and the like. Furthermore, the words "comprising", "including", "containing" and similar wordings does not exclude other elements or steps.

[0036] Brief descriptions of the drawings

[0037] The above objects, as well as additional objects, features and advantages of the present disclosure, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings.

[0038] Figure la-lc depicts illustrative views of the device according to an embodiment of the present disclosure.

[0039] Figure 2 depicts a block diagram depicting the arrangement according to an embodiment of the present disclosure. Figure 3 depicts a flow chart depicting the method according to an embodiment of the present disclosure.

[0040] Detailed description

[0041] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person.

[0042] Fig. la-lb show the first aspect of this disclosure being a device 100 for protecting a circuit during activation of a reserve battery 110 (further illustrated in Fig. lc). The device 100 comprises a reserve battery 110 and a sensor 120. The reserve battery 110 is inactive until activation, i.e., the reserve battery is a so-called reserve battery (not to be mistaken for a backup battery). The reserve battery 110 is configured to power a load 202. The sensor 120 is configured to determining if the potential over the terminals 110a of the reserve battery 110 fulfils a predetermined criterion. An example of such criterion is that the electrical potential over the terminals 110a is above a predetermined threshold e.g., 1500 mV. The criterion is set such that the electrical potential in the reserve battery is determined to be sufficiently high so that the reserve battery 110 can power the load 220. Further, the criterion is set such that it reduces the risk of developing internal resistances during the activation phase of the reserve battery 110.

[0043] Nevertheless, until said criterion is fulfilled, the reserve battery 110 is not connected to the load 202. The operation of connecting the battery 110 to the load 202 is controlled by a control unit 130. The control unit 130 is thereby configured to electrically connect the reserve battery 110 to the load 202 when said predetermined criterion is fulfilled (seen in Fig. lb).

[0044] The reserve battery 110 comprises a cell stack 112 and an ampoule 117 which comprising electrolyte 117a. The ampoule 117 is configured to break upon experiencing an acceleration above a predetermined threshold in at least one predetermined direction. For example, if the device 100 is located in a grenade launched into the air, the acceleration of the grenade will cause the ampoule to break (see further details below). The ampoule 117 is configured to break such that the electrolyte 117a will be enabled to reach the cell stack 112. The reserve battery 110 is configured to guide the electrolyte 117a into the cell stack 112, thereby forming a closed circuit for at least part of the reserve battery 110 thereby activating the reserve battery 110. When the electrolyte 117a reached the cell stack 112 the electric potential in the battery 110 start to increase.

[0045] The reserve battery 110 comprises a damping element 114 in which the ampoule 117 is arranged. The object of the damping element 114 is to protect the ampoule 117 from undesired breaking. In other words, the damping element 114 is arrange to hold and protect the ampoule 117 until it is time to activate the reserve battery 110.

[0046] The glass ampoule 117 is configured to easily break when leaving the damping element 114. Preferably, the ampoule 117 is a glass ampoule 117.

[0047] The sensor 120 is a low-power sensor 120 configured to not affect the potential over the reserve battery 110 such that the reserve battery 110 can reach the potential over the terminals of the reserve battery 110 in order to fulfil the predetermined criterion without being affecting by the power needed by the low-power sensor 120.

[0048] The device 100 comprises a switch 130a being operatively connected to the control unit 130, and the switch 130a is configured to electrically connect the reserve battery 110 to the load 202 when the predetermined criterion is fulfilled.

[0049] In other words, the switch 130a is configured to, when the predetermined criterion is fulfilled, move from an initially open state sO (Fig. la) to a closed state si (Fig. lb), wherein the closed state si electrically connects the reserve battery 110 to the load 202.

[0050] The device 100 comprises a timer 140. The timer 140 is a low energy timer, which is activated when the cell stack 114 reaches predetermine level.

[0051] When the timer 140 is activated, a predetermined time starts to countdown. The countdown time is long enough to secure that the electrolyte 117a has been distributed and the reserve battery 110 has obtained a predetermined charge sufficient to drive the load 202.

[0052] Since the time in which the reserve battery 110 reaches the predetermined charge to drive the load may varies. The timer 140 reduces the fluctuation in time of when to connect the reserve battery 110 to the load 202, i.e., the variation in time from the breaking of the ampule until the reserve battery 110 connects to the load 202 is reduced. Since the 140 is a low energy timer, the timer 140 is enable to more or less start at the same time regardless of the viscosity of the electrolyte 117a. However, as stated above, the time it takes for electrolyte 117a to be distributed in the cell stack and leading to that the reserve battery 110 reaches the predetermined charge to drive the load varies. The predetermined time is configured to be long enough such that the variation of the viscosity of the electrolyte 117a is limited. When the countdown has ended the reserve battery 110 is electrically connects the to the load 202.

[0053] For example, if the electrolyte has lower viscosity, the electrolyte will be distributed faster than in another example in which the electrolyte has higher viscosity. In both scenarios, the timer 140 is set to a predetermined time which is long enough to secure that the reserve battery 100 has obtained a predetermined charge regardless of the current viscosity of the electrolyte 117a.

[0054] Figure lc show a close up schematically illustration of a reserve battery 100. The figure depict that the electrolyte 117a is separated from the cell stack 114 by the ampoule 117. The damping material at least partly cover the ampoule 117 and protects the ampoule 117 from unintentional breaking. The ampoule 117 is configured to move from the damping device 114 and break upon impact on a structure 118. The electrolyte 117a will then be guided in to the cell stack 112.

[0055] Figure 2 shows the second aspect of this disclosure being an arrangement 200 for an explosive device. The arrangement comprises a load 204 comprising an explosive charge 204. The arrangement also comprises the device 100 according to the first aspect.

[0056] The arrangement 100 may be a grenade or a missile, or a part thereof. In one example, the arrangement 100 is a grenade launched from a grenade launcher (not shown). The force driving the grenade forward towards a target will create an acceleration force acting on the grenade causing the ampule 117 to move from the damping element 114 and thereby break. The electrolyte 117a comprised in the ampoule 117 will be guided and distributed into the cell stack 112. The electrolyte 117 will thereby forming a closed circuit for at least part of the reserve battery 110 and in that way activating the reserve battery 110. The activation phase of the reserve battery 110 is thereby initiated.

[0057] Figure 3 shows the third aspect of this disclosure. Fig.3 shows a method for protecting a circuit during activation of a reserve battery 110 comprised in a device 100 according to the first aspect. The method comprises the following steps:

[0058] Activating 310 the reserve battery 110.

[0059] Optionally, the step of activating 310 the reserve battery 110 comprises the steps of:

[0060] Breaking 310a the ampoule 117 which comprises the electrolyte 117a; and Distributing 310b the electrolyte 117a into the cell stack 112, which is located in the reserve battery 110.

[0061] Determining 320a if the potential over the terminals of the reserve battery 110 fulfils a predetermined criterion.

[0062] Determining 320b if a predetermined time has elapsed since the reserve battery 110 was activated 310.

[0063] Electrically connecting 330 the reserve battery 110 to a load 202, if the criterion is fulfilled, and / or if a predetermined time has elapsed since the reserve battery 110 was activated 310.

[0064] Optionally, the method 300 may further comprises a step of

[0065] Accelerating 301 the device 100, which precedes the step of activating 310 the reserve battery.

[0066] The person skilled in the art realizes that the present disclosure is not limited to the preferred embodiments described above. The person skilled in the art further realizes that modifications and variations are possible within the scope of the appended claims. Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed disclosure, from a study of the drawings, the disclosure, and the appended claims.

Claims

CLAIMS1. A device (100) for protecting a circuit during activation of a reserve battery (110), wherein the device (100) comprises: a reserve battery (110) which is inactive until activation, wherein the reserve battery (110) is configured to power a load (204); and a sensor (120) configured to determining (320) if the potential over the terminals (110a) of the reserve battery (110) fulfils a predetermined criterion; and a control unit (130) configured to electrically connect (330) the reserve battery (110) to the load (204) when the predetermined criterion is fulfilled, wherein the reserve battery (110) comprising: a cell stack (112); and an ampoule (117) comprising electrolyte (117a), wherein the ampoule (117) is configured to break upon experiencing an acceleration above a predetermined threshold in at least one predetermined direction; and wherein the reserve battery (110) is configured to, upon the ampoule (117) breaking, guide the electrolyte (117a) into the cell stack (112), thereby forming a closed circuit for at least part of the reserve battery (110) thereby activating the reserve battery (110).

2. The device (100) according to any of the preceding claims, the reserve battery (110) comprising a damping element (114) in which the ampoule (117) is arranged.

3. The device (100) according to any of the preceding claims, wherein the ampoule (117) is a glass ampoule (117).

4. The device (100) according to any of the preceding claims, wherein the sensor (120) is a low-power sensor (120) configured to not affect the potential over the reserve battery (110) such that the reserve battery (110) can reach the potential over the terminals of the reserve battery (110) in order to fulfil the predetermined criterion without being affecting by the power needed by the low-power sensor (120).

5. The device (100) according to any of the preceding claims, further comprises a switch (130a) which is operatively connected to the control unit (130), and the switch (130a) is configured to electrically connect the reserve battery (110) to the load (204) when the predetermined criterion is fulfilled.

6. The device (100) according to claim 5, wherein the switch (130a) is configured to, when the predetermined criterion is fulfilled, move from an initially open state (sO) to a closed state (si), wherein the closed state (si) electrically connects the reserve battery (110) to the load (204).

7. The device (100) according to any of the preceding claims, wherein the device (100) further comprises a timer (140).

8. An arrangement (200) for an explosive device, comprises: a load (204) comprising an explosive charge (204); and the device (100) according to any of claim 1-7.

9. A method (300) for protecting a circuit during activation of a reserve battery (110) comprised in a device (100) according to claim any of claim 1-7, the method comprises the following steps: activating (310) the reserve battery (110); determining (320a) if the potential over the terminals of the reserve battery (110) fulfils a predetermined criterion and / or determining (320b) if a predetermined time has elapsed since the reserve battery (110) was activated (310); electrically connecting (330) the reserve battery (110) to a load (204), if the predetermined criterion is fulfilled and / or if the predetermined time has elapsed since the reserve battery (110) was activated (310).

10. The method (300) according to claim 9, where in the step of activating (310) the reserve battery (110) comprises: breaking (310a) the ampoule (117) comprising electrolyte (117a); and distributing (310b) the electrolyte (117a) into a cell stack (112) comprised in the reserve battery (110).

11. The method (300) according to any of claim 9-10, wherein the method (300) further comprises a step of accelerating (201) the device (100), which precedes the step of activating (310) the reserve battery.

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