WO2005093883A1

WO2005093883A1 - Reserve battery and its activation system

Info

Publication number: WO2005093883A1
Application number: PCT/EP2005/051370
Authority: WO
Inventors: Gerard Johan Martin Versleijen; Jos Jeroen Dijkshoorn; Emiel Van De Werf; Johannes Adrianus Straver
Original assignee: Thales Nederland B.V.
Priority date: 2004-03-29
Filing date: 2005-03-24
Publication date: 2005-10-06
Also published as: NL1025841C2

Abstract

This invention relates to high energy density batteries, of a reserve type, designed for long storage lifetime and fast activation, and their activation system. This invention solves the volume drawbacks of reserve battery's mechanical activating system using detonating means, which occupy less space. So, an object of this invention is a reserve battery's activation system adapted for breaking the reserve battery's container such that the battery is activated comprising an activating signal generator providing an activating electric signal and detonating means which are ignited by said activating electric signal. A further object of this invention is to provide an alternative to mechanical activating system for avoiding their drawbacks (dependency to environmental influences, geometrical tolerances, complexity and the usage of moving parts) with the above-described activating system whose activating signal generator is electronically implemented. By this way, the reserve battery's activation system is reduced again in term of volume.

Description

Reserve battery and its activation system

This invention relates to high energy density batteries, of a reserve type, and their activation system designed for long storage lifetime and fast activation.

In some applications, batteries are required which may be retained in inventory and storage for a long time before being called upon for use. Moreover, such batteries shall be kept in inactive condition during storage, but be subject to simple and rapid activation when they are placed into service. Furthermore, such batteries could have to be effective in operation in environments that may be subjected to very low sub-zero temperatures or very high terrestrial temperatures.

Developments in high energy density battery systems provide greater energy density than do conventional batteries. Therefore, such high- energy battery systems are adapted to many applications where the batteries are to be stored for long periods of non-use and to be available, immediately, for use in emergency situations.

For this object, reserve type batteries have been provided utilising such high-density battery cells, so they will be available for applications where the battery may be kept in storage and held in reserve for relatively long periods of time before being called into service.

In certain such applications, the battery should be able to be stored for a long period, up to 15 years, before the battery is called into service, and be able to be activated for immediate service when desired. For such purpose, reserve battery principles have been adapted to the high energy density systems like those based on lithium for example. The low temperature performance of the batteries of these systems is substantially better than those of conventional batteries. The primary high energy density batteries show good capacity retention for storage at room temperatures for only 1 to 2 years.

The degradation of the cell performance on storage is predominantly associated with the reactive lithium anode. The storage deficiencies of the high energy density systems are therefore obviated by the use of reserve type structures in which the electrolyte is kept isolated from the lithium anode, in a separate reservoir, during storage. In such an arrangement, a storage life of fifteen years is obtained without problems.

An example of such lithium reserve batteries contains a lithium anode, a carbon cathode and an organic electrolyte consisting of a mixture with liquid sulphur oxide.

In such batteries, a simple activating system is provided to simultaneously activate all the cells by opening the reservoir in each of the respective cells, to release the electrolyte and render each associated cell active.

These reserve cell batteries have to be able to fulfil several partially contradictionary requirements: survive drop tests acceleration and automatic gun loading system acceleration without activation versus activation at gun firing, whereas acceleration levels witnessed at gun firing be below those reached at drop tests and automatic loading.

Previously, the differentiation between drop test, automatic loading and gun firing is fulfilled by a mechanical system (e.g. acceleration force against spring load, breaking of a support under acceleration, acceleration force against mass inertia as described by the patent application filed under n° EP 03 104126), which initiates the opening of the electrolyte container.

One drawback of these mechanical systems is their dependency on the mechanical components with respect to different environmental influences, geometrical tolerances, complexity and the usage of moving parts. Due to these dependencies, the volume of the battery using mechanical activation systems may be too large for some applications, knowing that the current requirements for any kind of application are the reduction of the occupied space.

Another drawback of these mechanical systems is that the activation is a function of the acceleration. Considering, for example, some fuzes having the following properties: gun firing minimum acceleration about 1 000 g, drop test acceleration about 5 000 g and flick ramming (automatic loading) acceleration up to 5 000 g in the opposite direction. It is easy to understand that only complex mechanical activation systems can resist 5 000 g and break the container at only 1 000 g. Thus, these mechanical systems are normally only working when the gun firing acceleration is above the acceleration reached by the drop tests and automatic loading, so in a specific range of acceleration.

This invention solves the volume drawbacks using detonating means, which use little space. These detonating means are placed on or close to the container within the battery housing, for opening the container filled with electrolyte.

So, an object of this invention is a reserve battery's activation system for breaking at least one reserve battery's container by shock-wave such that the battery is activated, the container being hermetically closed said activation system comprises an activating internal signal generator providing an activating electrical signal and detonating means providing a shock-wave which are ignited by said activating electrical signal.

Advantageously, detonating means are not affecting the chemistry of the reserve battery's cell and/or the reserve battery's electrolyte during battery operation.

A further object of this invention is to provide an alternative to mechanical activating systems for avoiding their drawbacks (dependency to environmental influences, geometrical tolerances, complexity and the usage of moving parts) with the above described reserve battery's activation system whose activating signal generator is electronically implemented inside the hermetically sealed battery. By this way, the reserve battery's activation system is reduced again in term of volume.

Another embodiment of this invention is to allow activation even though acceleration levels witnessed at gun firing are below those reached at drop tests and automatic loading. For this purpose, the above mentioned activating signal generator discriminates between a short and a long acceleration upon predetermined acceleration duration.

The invention relates also to a reserve battery comprising: - a cell of electrodes, - a hermetically closed container filled with a liquid electrolyte, - a housing in which the said cell and the container are placed, and - an activating system as described previously placed at least partially within the housing. When opening the container by igniting said activation system's detonating means, the electrolyte is sprayed over the anode -cathode of the cell activating the battery faster than with any other mechanical activating system.

Further features and advantages of the invention will be apparent from the following description of examples of embodiments of the invention with reference to the drawing, which shows details essential to the invention, and from the claims. The individual details may be realised in an embodiment of the invention either severally or jointly in any combination. -Figure 1, a scheme of a reserve battery with an activation system, according to the invention, -Figure 2, a diagram giving drop test, flick ramming and firing accelerations examples of the reserve battery in fuze applications, -Figure 3, a scheme example of the activating signal generator according to the invention, -Figure 4, a scheme of a piezo element used as sensor means and power source in the activating signal generator according to the invention, -Figures 5a and 5b, diagrams showing the voltage at the piezo element 31 output, at the capacitor 327 and at the igniter I respectively during a short and a long acceleration, -Figure 6, a scheme of a system of batteries having a common activation system. In the following, the explanation will be given for the specific application of gun fired ammunition, but the described activation system may be used in any application using reserve battery.

Figure 1 shows a scheme of a reserve battery with an activation system 30 (see Figure 3) according to the invention, the reserve battery being hermetically closed. A reserve cell battery as used in gun fired ammunition is a battery in which typically the liquid electrolyte 22 is stored inside the battery's housing 40, separated from the anode-cathode cell 10, in a hermetically closed container 21 within the battery's housing 40. The activation system comprises an activating internal signal generator 31-32 providing an activating electric signal to detonating means 33. The detonating means 33, e.g. a pyrotechnical device, are placed on the container 21 (e.g. glued on the glass of the container 21) or sufficiently close to the container 21 such as the detonating means's detonation breaks the container 21. The activating signal generator 31 ,32 is electronically implemented inside the hermetically sealed battery.

The velocity of the electrolyte release is independent of acceleration level because of the detonation force. Actually, the detonating means's blast sprays the electrolyte 22 through the battery over the cell 10. Such a detonating activation system 30 activates the battery faster than existing activation systems, fulfilling in this way one of the main requirements for batteries. Moreover, this kind of activation does not affect the battery's chemical elements. Indeed, the detonating means 33 are not affecting the chemical elements of the reserve battery's cell 10 and/or the reserve battery's electrolyte 22 during battery operation. Furthermore, it is easy to see that such detonating activation system 30 occupies little space within the battery's housing 40 compared with mechanical activation systems.

An advantageous embodiment of this invention, as an alternative to mechanical activation systems, is for reserve battery activation system development the choice of an electronic implementation. The purpose of the battery in gun firing application is to be activated only at gun firing not at drop test neither at flick ramming even tough acceleration levels witnessed at gun firing are below those reached at drop tests and automatic loading.

The accelerations during the drop-, flick ramming- and firing low charge events can be expected in the proportion shown in figure 2. Figure 2 gives the acceleration G in m/s² on the Y-axis in function of the time t in ms on the X-axis. The dashed curve A1 represents a drop test acceleration, the dotted curve A2 a flick ramming acceleration and the dashed-dotted curve A3 a firing low charge acceleration. As seen with the examples of figure 2:

- the drop's peak acceleration is around 55000 m/s² and its acceleration duration around 0.1 ms;

- the flick ramming peak acceleration is around 35000 m/s² and its acceleration duration around 0.2 ms; - the firing low charge's peak acceleration is around 9000 m/s² and its acceleration around 6.0 ms.

More generally, the drop test and flick ramming acceleration have usually a time base below 1 ms, whereas the gun firing acceleration has a time base above 5 ms.

So, another advantageous embodiment of this invention is an activation system 30 capable of discriminating between short and long acceleration durations, e.g. for discriminating on one hand drop test A1 and flick ramming A2 events from on the other firing low charge A3 event. For example, the activation system 30 may comprise an element 31 as sensor means and power source for respectively measuring the acceleration and transducing it in an acceleration electric signal. Piezo elements are known as pressure sensor and may be used as acceleration sensor due to this pressure measurement function. For this purpose, the element 31 may be a piezo element used as both sensor means and power source. The piezo element 31 transduces an increasing axial forward acceleration into an electrical current.

The piezo element 31 may comprise a mass M and the piezo itself P as shown in more detail by the example of figure 4. This piezo P may comprise several layers (7 layers Lι-L on figure 4) depending on the acceleration to be measured and the power consumption of the electrical circuit.

The piezo element 31 is connected to an electrical circuit 32, which differentiates between different accelerations: short high and smaller but longer accelerations, e.g. respectively caused by drop test A1 and automated loading A2 (also called flick ramming) on the one hand and by an actual gun firing A3 on the other (in the gun fired ammunition applications) by discriminating between the characteristic time scale events. If the circuit 32 decides that it is fired with a gun, it will ignite a pyrotechnical device 33, which releases the electrolyte 22 from the container 21.

So, as the activation is not based on the acceleration force but on time effects of events, rotation is not required for activation as in some mechanical activation systems. Figure 3 shows a sensor-electrical activating signal generator 31-

32. This activating signal generator comprises an element 31 as sensor means and power source. These two functions may also be separated in two connected elements (not shown). The sensor means measure the acceleration in time. The power source provides acceleration electric signal function of the measured acceleration, this acceleration electric signal will be use to ignite the pyrotechnical device 33. This element 31 is coupled to an electric circuit used as threshold means 32.

These threshold means 32 discriminate between the duration of the measured accelerations and a predetermined acceleration duration such as the threshold means provide an activating electric signal when the measured acceleration has a longer duration than the predetermined acceleration duration.

As shown by figure 3, the electric circuit may comprise standard available components: e.g. Zener diode 321 , resistances 321-322-323-326- 328, transistors 324-325, and capacitors 327-329. This electric circuit is powered by the piezo element 31 and charges a capacitor 327 within a fixed duration (e.g. corresponding to a predetermined acceleration duration allowing to discriminate between short and long duration independently of the acceleration increase). When the capacitor 327 is charged, the electrical circuit 32 releases the charge of the capacitor 327 to the pyrotechnical device 33.

The voltage threshold is a function of the predetermined acceleration duration above which the detonating means are ignited. This voltage threshold is fixed by the electrical components used comprised between the element 31 and the capacitor 327.

The predetermined acceleration duration, in gun firing ammunition applications, depends on, and is fixed to discriminate between, on the one hand drop and flick ramming acceleration duration and on the other hand firing low charge acceleration duration. E. g. for the examples of acceleration durations given by figure 2, the predetermined acceleration duration may be fixed between 2 and 5 ms. A safety resistor 328 could be used to avoid unintended ignition.

The threshold means comprise this safety resistor 328. This safety resistor conducts a leakage current such that the capacitor will always be emptied.

Using such an electric circuit as threshold means 32 for discriminating between the acceleration duration of different events allows tuneable activation time by changing standard electrical components 321- 329.

Another advantage of using such an electric circuit as threshold means 32 is that the electrical-detonating activation system 30 is cheaper than mechanical activation systems, as the electrical components are off- the-shelf components.

A further advantage using electrical-detonating activation system 30 is that at least some parts of the electrical-detonating activation system 30 : the activating signal generator 31-32 can be tested before use, and even be re-used which is not the case with a mechanical activation system.

The pyrotechnical device 33 is ignited by the electrical circuit 32 and opens the container 21.

Figures 5a and 5b show the voltage at the piezo element 31 output, at the capacitor 327 and at the igniter I, respectively during a short

A1 , A2 and a long acceleration A3. These examples are given for a piezo element 31 with a 5nF piezo capacitance providing a 300μA current at 23°C. The voltages are given in Volt on the Y-axis as function of time t in ms on the X-axis.

As shown with figure 5a, for a short acceleration - e.g. drop test A1 or a flick ramming A2-, the acceleration decreases before the capacitor is charged. This implies that the voltage \ (dotted curve) produced by the element 31 decreases, so the voltage V₂ (dashed dotted curve) at the capacitor 327 decreases before the capacitor 327 is charged. Thus, as shown by the plain line, the capacitor 327 does not transmit its charge to the igniter I: the voltage V₃ at the igniter remains zero and the igniter I does not provide the activating electric signal to the detonating means 33. So, the battery is not activated.

As shown with figure 5b, for a long acceleration -e.g. firing low charge A3, the acceleration increases during a sufficiently long duration for the capacitor to be charged. This implies that the voltage \ (dotted curve) produced by the element 31 increases and remains at a saturation level during a sufficiently long duration, so the voltage V₂ (dashed dotted curve) at the capacitor 327 increases during a sufficiently long duration to charge the capacitor 327. Thus, as shown by the peak of the plain line, the capacitor 327 transmits its charge to the igniter I: the voltage V₃ at the igniter shows a peak when the capacitor transmits its charge and the igniter I provides the activating electric signal to the detonating means 33. So, the battery is activated.

As shown by figure 6, the activation system could be common to many batteries, e.g. N batteries: one activating signal generator 31-32 is common to all the batteries being coupled to the detonating means 33 33_N of each batteries Bi to B_N. Thus, it is also possible to one battery whose activation system is split in two parts: the first part, detonating means 33, within the battery housing 40 and the second part, activating signal generator 31-32, outside the battery housing 40.

Reserve battery with such detonating activation system may be used by linear motor and more generally by any driven mechanical system.

Another application to this electrical-detonating activation system is in all kinds of collision-based activation systems of reserve type batteries in transport applications.

More generally, such activation system may be any reserve battery whose volume requirements are too low for allowing the use of existing activation systems.

Claims

1. Reserve battery's activation system for breaking at least one reserve battery's container by shock-wave (21) such that the battery is activated characterised in that, the container being hermetically closed said activation system (30) comprises an activating internal signal generator (31 , 32) providing an activating electrical signal and detonating means (33) providing a shock-wave which are ignited by said activating electrical signal.

2. Reserve battery's activation system according to the preceding claim characterised in that the detonating means (33) are not affecting the chemistry of the reserve battery's cell (10) and/or the reserve battery's electrolyte during battery operation.

3. Reserve battery's activation system according to any of the preceding claims characterised in that the activating signal generator (31 ,32) is electronically implemented inside the hermetically sealed battery.

4. Reserve battery's activation system according to any of the preceding claims characterised in that the activating signal generator (31 ,32) discriminates between a short (A1 , A2) and a long acceleration (A3) upon a predetermined acceleration duration.

5. Reserve battery's activation system according to the preceding claim characterised in that the activating signal generator (31 ,32) comprises sensor means for measuring the acceleration, a power source for providing an acceleration electric signal function of the measured acceleration, threshold means (32) for discriminating the duration of the measured accelerations upon a predetermined acceleration duration such as the threshold means provides an activating electric signal when the measured acceleration has a longer duration than the predetermined acceleration duration.

6. Reserve battery's activation system according to the preceding claim characterised in that a piezo element (31 ) comprises both the sensor means and the power source.

7. Reserve battery's activation system according to the preceding claim characterised in that the threshold means (33) comprises a capacitor (327), which is charged during the measured acceleration duration.

8. Reserve battery's activation system according to the preceding claim characterised in that the threshold means comprise a safety resistor (328) such as said resistor avoids unintended activating electric signal.

9. Reserve battery comprising: - a cell (10) of electrodes, - a hermetically closed container (21 ) filled with a liquid electrolyte (22), - a housing (40) in which the said cell (10) and the container (21) are placed, and - an activating system (30) according to any of the preceding claims placed at least partially within the housing (40).

10. Reserve battery according to the preceding claim characterised in that the detonating means (33) are placed on or close to the container (21).

11. Reserve battery according to any of the preceding claims characterised in that the detonating means (33) and the container (21) are placed such that the detonating means' detonation breaks the container (21 ).

12. Reserve battery according to any of the preceding claims characterised in that the detonating means (33) and the container (21) are placed such that the detonating means' detonation sprays the electrolyte (22) over the cell (10).