RU2559841C1 - Device for protection of lithium-ion battery - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention relates to switching or locking bypass devices installed in parallel with each lithium-ion battery of space vehicle. Device comprising casing, fixed and movable contacts, electric heating and thermal elements, additionally has elastic and resilient membrane. The movable contact is made out of low-melting alloy and is arranged together with the electric heating element in the cavity limited by the casing, elastic membrane and one fixed contact. The cavity between the casing and elastic and resilient membranes is by one third filled with liquid with low specific heat of evaporation, acting as thermal element. In fixed contacts holes are made.

EFFECT: increased reliability of response, assurance minimum transient resistance of contacts and continuity of circuit during the battery operation as part of power supply system of the space vehicle during the entire service life.

3 dwg

Description

The present invention relates to electrical engineering and relates to switching (or rather, blocking) bypass devices installed in parallel to each of the batteries of the battery of the spacecraft (SC).

During the operation of rechargeable batteries (AB) as part of the spacecraft’s power supply system over a period of active life (CAC) of 10-15 years, a defect is likely to occur — a short circuit in one or more batteries connected in series. In this case, it is necessary to ensure that the discharge current of the remaining batteries flows around the defective battery, provided that the common circuit is continuous.

Known thermosensitive switch [1], containing a housing in which are movable and fixed contacts and a thermosensitive element made of foil tape material with a shape memory effect, adopted as an analogue.

The disadvantage of the above analogue is the impossibility of large currents flowing through its contacts - of the order of tens of amperes - with which the batteries of modern spacecraft are discharged. The scope of the analogue is limited to the alarm of the limit temperature, i.e. using as a sensor, thermal relay, thermal fire detector. The required transient resistance (not more than 150-200 μOhm) cannot be achieved in acceptable weight and size limitations only due to a thermosensitive element with a shape memory effect.

Closest to the claimed device is a bypass switch [2], adopted for the prototype, consisting of a housing with a working spring located in it, an actuator with a movable contact, fixed contacts, a fuse, a power actuator based on a thermosensitive element with a shape memory effect, an electric heating element .

The specified prototype has disadvantages arising from the operating conditions that occur during normal operation: space vacuum and CAC for 10-15 years.

Under the conditions of cosmic vacuum, the effect of the so-called diffusion welding is manifested, when during the “removal” from the surfaces of movable and fixed contacts, which are pre-springed, the latter self-clean at the atomic level, and the contact that was movable becomes stationary and the bypass device ceases to fulfill its target function, although with all ground tests, including acceptance tests, the device is working properly.

In addition, the working spring (position 2 in the description of the prototype) is during the CAC in a prestressed state. This is accompanied by a "draft" of the spring, when it cannot fully restore its original shape, and the force developed by it decreases.

The problem solved by the claimed device is to ensure the reliability of operation with continuity of the circuit and a minimum contact resistance of the contacts.

This problem is solved due to the fact that the inventive device for protecting a lithium-ion battery, consisting of a housing and fixed and movable contacts located therein, electric heating and heat-sensitive elements, elastic and elastic membranes, while the movable contact is made of fusible alloy and placed together with an electric heating element in a cavity bounded by a housing, an elastic membrane and one of the fixed contacts, and the cavity between the housing and the elastic and elastic membranes and a third is filled with a liquid with a low specific heat of vaporization, which simultaneously performs the role of a heat-sensitive element, and holes are made in the fixed contacts.

The technical result is achieved by the fact that in the proposed technical solution there are no prestressed links (springs), and the functions of the heat-sensitive element and the power drive are combined.

The invention is illustrated by drawings, which depict the following.

In FIG. 1 shows the inventive device in its original state.

In FIG. 2 - in activated.

In FIG. 3 shows the connection diagram of the device to the battery.

The device comprises a housing 1, fixed contacts 2 with holes 3, an electric heating element 4, covered with a layer of electrical insulation, located in the cavity between one of the fixed contacts, which is connected electrically and by an elastic membrane 5, the cavity is filled with fusible alloy 6, which is in the initial state in solid phase, on the other hand from the elastic membrane 5, in the cavity 7 there is a liquid with a low specific heat of vaporization, which simultaneously performs the role of a heat-sensitive element, the volume of the cavity 7 filled by a third and bounded by an elastic membrane 8, which in the initial state is not stressed.

The device is connected to the positive burner 10 of the battery An with a fixed contact 2, which is electrically connected to one of the contacts of the electric heating element 4, the second contact of which is connected to the cathode of the diode 9. Another fixed contact 2 and the anode of the diode 9 are connected to the negative boron 11 of the battery An.

The device operates as follows. During operation of the battery in one or more batteries, a partial damage to the separator may occur due to a technological defect or violation of the operating conditions. If a short circuit occurs in the battery — a local local defect of the electrode block — it will begin to discharge with the total load current and current arising from a local defect that only heats the battery. In such an emergency, a defective battery will begin to quickly lose its residual capacity, as compared to serviceable ones. Its electrode block warms up and the battery is depressurized. Further development of the emergency situation is the “drying up" of the electrode block when the electrolyte vapor leaves the gap between the boron and the melted insulator. The consequence of this will be a breakdown of the faulty battery, and the voltage on its bourne will be reversed (reverse polarity), as the battery circuit remains closed through the load.

During the polarity reversal, the diode 9 is connected, connected in series with the electric heating element 4, the resistance of which is selected from the condition of a voltage drop of about 2.5-3 V, when the load current flows through it, but the current circuit is not interrupted, and the power dissipated on the electric heating element 4, is about 50-60 watts.

The low-melting alloy 6 passes into the liquid phase, the liquid in the cavity 7 passes into the gaseous phase, the vapor pressure in the cavity 7 increases. This leads to the deformation of membranes 5 and 8, and the low-melting alloy 6, which plays the role of a movable contact, is forced out through holes 3 in one of the fixed contacts 2 from the cavity 6 into the intercontact space, shorting them.

The volume of the fusible alloy is selected with a certain margin, the excess of which passes through the holes 3 in another fixed contact. The voltage between the fixed contacts 2 drops to zero, the diode 9, connected in series with the heating element 4, is locked, the temperature of the alloy 6 decreases, and it again goes into the solid phase.

Given that the device is located directly on the battery, an increase in its temperature to + 40- + 60 ° С will also cause an increase in the temperature of the low-melting alloy 6 and liquid with a low specific heat of vaporization, which act as a heat-sensitive element. The remaining Δt ° before melting of the low-melting alloy 6 and boiling of a liquid with a low specific heat of vaporization is overcome in 2.5-3 sec.

The technical efficiency of the claimed device, in contrast to the prototype, lies in the fact that there are no prestressed elements (springs) in it, and the sliding spring-loaded contacts are replaced by a contact made of a low-melting alloy, which is not subject to diffusion welding in vacuum, which ensures its reliability , continuity of the battery circuit and minimum transition resistance between the contacts during operation of the battery as part of the spacecraft power supply system for the entire CAC for 10-15 years.

An example of a specific implementation. To ensure uniform distribution of the fusible alloy 6 in the cavity between the contacts 2 (Fig. 2), the holes 3 are staggered. The electric heating element 4 must be electrically isolated from the low-melting alloy 6, for which it is covered with alundum, similarly to how the heater is isolated from the cathode in electric vacuum devices. As the fusible alloy 6, a Wood alloy can be selected with a melting point of 65 ° C. The elastic membrane 5 must be an electrical insulator, have a sufficient margin of linear elongation and at the same time be resistant to elevated temperatures, a polymer film such as fluoroplastic meets these requirements. Ethyl alcohol with a boiling point of + 78 ° C can serve as a liquid with a low specific heat of vaporization. Because in the activation mode of the device through the diode 9 the load current of the battery will flow, then in order to dissipate as little power as possible on it, it should be selected with a Schottky barrier.

Information sources

1. RF patent No. 22010129, IPC Н01Н 37/46, Н01Н 37/32, Н01Н 61/06, 2003.

2. RF patent No. 2415489, IPC Н01Н 37/00, 2006.

Claims (1)

 A device for protecting a lithium-ion battery, consisting of a housing and fixed and movable contacts located therein, electric heating and thermosensitive elements, characterized in that elastic and elastic membranes are additionally introduced into it, while the movable contact is made of fusible alloy and placed together with an electric heating element in a cavity bounded by a housing, an elastic membrane and one of the fixed contacts, and a cavity between the housing and the elastic and elastic membranes and a third full of liquid with a small specific heat of vaporization simultaneously performs the role of the thermally responsive member, the stationary contacts in the openings.

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