DE102009002253A1 - Battery system with external circuit - Google Patents

Abstract

The invention relates to a battery system comprising: a) a battery having one or more cells; b) a measuring and control unit which determines the temperature and / or the voltage of individual, several or all battery cells continuously or periodically; c) an external circuit electrically connectable to the poles of the battery via one or more switches so that power can flow from one battery terminal to the other battery terminal via the external circuit; wherein the control unit controls the position of the switch or switches such that when exceeding a predetermined heat output and / or exceeding a predetermined voltage drop rate, the external circuit is conductively connected to the battery poles.

Description

State of the art

Vehicles, which require an electric machine to drive also an energy storage, usually an output voltage of ≥ 60 V DC or 25 V AC. With such high voltage sources special requirements for the protection of persons are required, so that appropriate protective measures are provided.

Usually Therefore, overcurrent protection with the help of fuses realized. In this way, the lines within the traction network against overheating and thus protected against fire.

kick within the energy store a short circuit on, for example through a perforation of a separator, so you can with this Do not recognize devices and methods described above.

By a short circuit inside a battery can be the battery or a battery cell in a critical state. In a Battery or battery cell in critical condition finds an unusual temperature and pressure increase instead. The consequence is often a so-called "burning through" the Battery or the battery cell, which destroys and even lead to the battery exploding.

A well-known source for a local short circuit within A lithium-ion battery is based on a dendrite formation in the lithium ion accumulator. When a dendrite is a certain size has reached, the dendrite can penetrate the Separatorfolie and perforate. This perforation then leads to a short circuit inside the battery.

task It is one or more disadvantages of the present invention Prior art to reduce or overcome. Especially It is an object of the invention to provide a battery system of reduces the consequences of a short circuit inside the battery or limited.

Disclosure of the invention

• a) eine Batterie mit einer oder mehreren Zellen;
• b) eine Mess- und Steuereinheit, die die Temperatur und/oder die Spannung einzelner, mehrerer oder aller Batteriezellen kontinuierlich oder periodisch bestimmt;
• c) einen externen Stromkreis, der mit den Polen der Batterie über einen oder mehrere Schalter elektrisch leitend verbindbar ist, so dass Strom von einem Batteriepol über den externen Stromkreis zum anderen Batteriepol fließen kann;

wobei die Steuereinheit die Stellung des oder der Schalter derart steuert, dass, bei Überschreitung einer vorher festgelegten Wärmeleistung und/oder bei Überschreitung einer vorher festgelegten Spannungsabnahmerate, der externe Stromkreis mit den Batteriepolen leitend verbunden wird.The object is achieved by providing a battery system, comprising:

• a) a battery with one or more cells;
• b) a measuring and control unit which determines the temperature and / or the voltage of individual, several or all battery cells continuously or periodically;
• c) an external circuit electrically connectable to the poles of the battery via one or more switches so that power can flow from one battery terminal to the other battery terminal via the external circuit;

wherein the control unit controls the position of the switch or switches such that when exceeding a predetermined heat output and / or exceeding a predetermined voltage drop rate, the external circuit is conductively connected to the battery poles.

The inventive solution is distinguished characterized by the consequences of an internal short circuit within a battery can be reduced. The invention Battery system has an external circuit, the only then conductively connected to the battery poles as soon as signs of an internal short circuit are detected. Once the external Circuit has been coupled, a current can be from the battery over flow the external circuit. The conductive parts of the external circuit are warming up. This will be energy removed from the battery with the short circuit and is not standing available to cause further damage in the battery. The heat inevitably in the short circuit is created, thus, from the short-circuit region to the entire battery cell or battery and the external circuit. By the invention Solution also leads to a reduction of the absolute discharge time the battery cell or the battery. This is the place of the Short circuit to a total reduced absolute maximum temperature.

The battery system according to the invention has one or more batteries, wherein a battery may each have one or more cells. For the purposes of the present invention, a battery can be understood to mean any energy store which stores energy by means of electrochemical processes. In particular, this includes energy storage to understand, which one or more in series and give if necessary, also contain parallel connected accumulator and / or battery cells. Preferred electrochemical energy stores can be battery cells, in particular of the type Pb - lead-acid battery, NiCd - nickel-cadmium battery, NiH2 - nickel-hydrogen battery, NiMH - nickel-metal hydride battery, Li-ion - lithium-ion battery, LiPo - lithium Polymer Battery, LiFe - Lithium Metal Battery, Li-Mn - Lithium Manganese Battery, LiFePO ₄ - Lithium Iron Phosphate Battery, LiTi - Lithium Titanate Battery, RAM - Rechargeable Alkaline Manganese, Ni Fe - Nickel-Iron Battery, Na / NiCl - Sodium Nickel Chloride High-Temperature Battery SCiB - Super Charge Ion Battery, Silver-Zinc Battery, Silicone Battery, Vanadium Redox Battery and / or Zinc Bromine Battery , The energy store can have one or more cells. The battery preferably has at least one lithium-ion cell.

The battery system according to the invention has at least one external circuit, which is electrically conductively connected to the poles of the battery via one or more switches, so that current can flow from one battery pole via the external circuit to the other battery pole. The external circuit preferably has a material with good conductivity, preferably of> 10 ⁶ S / m (at 25 ° C.), particularly preferably of> 10 × 10 ⁶ S / m, very particularly preferably of> 50 × 10 ⁶ S / m. The material having particularly good conductivity may be, for example, copper or a material having a conductivity not inferior to that of copper.

Of the external circuit has one or more switches. The switches are designed and positioned in such a way that over the position of the switches is a current flow from a first battery pole over the external circuit to a second Batteriepol regular and / or can be made controllable and / or interrupted. There are the switches in a position that has such a current flow interrupts and will be closed only if an appropriate Signal from the measuring and control unit is emitted. in principle All standard and / or controllable switch types can be used be used in electrical circuits. The expert has no difficulty selecting switch types and dimensions which used in combination with a selected battery can be. In particular, a relay can be used as a switch As long as the battery system in normal operation or runs in the loading mode, the switches are preferably open before and interrupt a flow of current through the external Circuit.

Prefers the external circuit is next to one or more switches and conductive connections essentially no further electrical Consumers on.

Of the external circuit may preferably have a resistance Re, which is lower than the resistance Rs of a standardized one Short circuit for a battery of the same type and the same Dimensioning like the battery used in the battery system. Thereby is achieved that the power is preferred over the external Circuit is flowing and not over the place of the battery internal Short circuit. The value of a standardized short circuit Rs can not be specified absolutely for all battery systems, but varies from battery type to battery type and hangs for the same battery type of the dimensioning of the used Battery off. The expert has no difficulty for a particular battery of known type and dimensions determine the value of a standardized short circuit Rs. To the expert can batteries of the same type and dimensions under different, standardized short circuit conditions test the achievable Rs value. The batteries are preferred same type and dimensioning under standardized Conditions tested, with the conditions to the respective, too expected operating conditions of the battery to be used are. The value of a standardized short circuit Rs can then for example, as an arithmetic mean of all or selected measured Rs values. The value of one standardized short circuit Rs can also be the lowest, under the permitted battery operating conditions expected or measured resistance value of a battery short circuit match or based on it.

Prefers the external circuit is isolated from the battery. there The external circuit can be thermally insulated from the battery be, and / or fireproof separated. Battery, Measuring and control unit and / or external circuit can be arranged in a common housing, wherein the external circuit an insulation and / or a device for at least partial cooling of the external circuit may include.

The external circuit can be configured at least partially cooled. In principle, any cooling principle can be used. Preferably, the electrical circuit to an air cooling, liquid cooling and / or one or more latent heat storage. The basic function of a latent heat storage is to absorb heat and release it when needed. It is characterized by a La tentwärmespeicher characterized in that a phase transition between a solid phase and a liquid phase with increasing heat input is not continuous. The temperature of a latent heat storage in the solid state increases continuously with increasing heat input. From a certain threshold temperature T _melt , the temperature of the latent heat storage remains constant despite further increasing heat input until complete melting of the medium in the latent heat storage, and only then increases again. Suitable latent heat storage are known in the art. In particular, latent heat storage can be used which contain paraffin or similar compounds.

The Battery system has at least one measuring and control unit, which is designed such that the temperature and / or the voltage single, multiple or all battery cells continuously or periodically is determinable. Suitable temperature and / or voltage measuring devices are known in the art. In doing so, the measuring function and the control function in two separate from each other Devices be realized or to a common unit summarized.

The Control unit is designed and positioned in the battery system, that it can control the position of the switch or switches. When exceeded a predetermined heat output and / or exceeded a predetermined voltage reduction rate, controls the control unit the position of the switch or switches such that the external circuit is conductively connected to the battery poles and a current flow is manufactured by a first battery pole over the external circuit towards a second battery pole.

absolute Values for the predetermined heat output and / or voltage decay rates can not be for everyone Battery systems according to the invention binding and depend on the selected battery type, the selected battery dimensioning and / or from the operating state. The expert has no difficulty for a selected battery corresponding values for determine the heat output and / or voltage reduction rate. Preferred are for the predetermined heat output and / or voltage decay values selected at a short circuit, but not during normal operation or a charging process of the battery used. there the value (s) can be set in such a way that when one or both values are exceeded with a significant probability of an internal short circuit in the Battery or a battery cell is present. The values are preferred selected so that the probability is greater than 80%, more preferably more than 95%, is very particular preferably more than 99%.

The present invention also includes an electrical load, containing a battery system according to the invention. It does not matter that consumers and the battery system form a structural unit, but that consumers and inventive Battery system so functionally in contact that the battery system can supply the consumer with electrical energy. In particular, can the consumer is a motor vehicle. Here are the term "motor vehicle" all powered vehicles that use a battery to power of at least one component of the motor vehicle, regardless of which drive these vehicles have. In particular, includes the term "motor vehicle" HEV (electric hybrid vehicles), PHEV (plug-in hybrid vehicles), EV (electric vehicles), fuel cell vehicles, as well as all vehicles that use a battery at least partially Use supply of electrical energy.

The Invention will be described below with reference to the accompanying drawings exemplified.

1 shows a schematic representation of a battery system according to the invention.

2 shows the heat output (W) of an external circuit battery system according to the invention with a current flow through the external circuit of 200 A / m ² and a diameter of the short circuit of 4.62 microns. Here, heat_internal = sum of the heat output at the location of the short circuit and heat output of the entire battery cell; heat_short = heat output at the location of the short circuit; heat_gen = heat output of the whole battery cell; heat_external = heat output of the external circuit; heat_trans_internal = heat transfer from the battery cell to the location of the short circuit; heat_trans_surround = Heat transfer from the environment to the battery cell.

3 shows the heat output (W) of a battery system without external circuit with a diameter of the short circuit of 4.62 microns (designation as in 2 ).

4 shows the temperature (° C) and voltage (V) over time in the battery cell and at the location of the short circuit with a short circuit diameter of 4.62 μm. Here, Cell temp, i = 0: temperature of the battery cell without external circuit; Cell temp, i = 200 A / m ² : temperature of the battery cell with external circuit at a current flow of 200 A / m ² ; Short temp, = 0: Temperature at the location of the short circuit without external circuit; Short temp, i = 200 A / m ² : temperature at the location of the short circuit with external circuit at a current flow of 200 A / m ² ; Voltage, i = 0: voltage during short-circuit without external circuit; Voltage, i = 200 A / m ² : Voltage during short-circuit with external circuit at a current flow of 200 A / m ² .

5 shows the electrochemical energy (Wh) released at one with a short-circuit diameter of 4.62 μm. I = 0: total electrochemical energy without external circuit; i = 200 A / m ² : total electrochemical energy with external circuit at a current flow of 200 A / m ² ; internal only, i = 200 A / m ² : internally released electrochemical energy with external circuit at a current flow of 200 A / m ² .

1

battery system

2

battery with plus and minus pole

3

external Circuit with resistance Re

4

switch

5

measurement and control unit

6

internal Short circuit with resistance Rs

Exemplary embodiment the invention:

In 1 an exemplary embodiment of the battery system according to the invention is shown. The battery system 1 has a battery 2 with two poles, one plus and one minus. The poles of the battery 2 are over a switch 4 with an external circuit 3 connected. The external circuit 3 has a resistance Re. During normal operation and / or during charging of the battery 2 is the switch 4 opened in front, allowing a current flow between battery 2 and external circuit 3 is interrupted. Furthermore, the battery system 1 a measuring and control unit 5 on which the temperature and voltage of the battery 2 measures over time. Kicks in the battery 2 an internal short circuit 6 with a resistance Rs, the temperature in the battery rises 2 suddenly and the voltage across the battery 2 suddenly takes off. Exceeding a predetermined heat output and / or exceeding a predetermined voltage drop rate causes the measuring and control unit 5 the closure of the switch 4 and the external circuit 3 will be with the poles of the battery 2 conductively connected. Now at least a part of the energy of the cell can be connected via the connected external circuit 3 from the battery 2 subtracted from. If the resistance Rs> Re, the current even flows preferably via the external circuit 3 and the consequences of the internal short circuit 6 for the battery 2 are diminished.

Simulation of a battery system according to the invention with a short-circuit diameter of 4.62 μm (corresponds to a resistance Rs of 0.01 ohm m ² ):
The simulation was simulated with the "Dualfoil" model Doyle et al. Doyle, TF Fuller and J. Newman, J. Electrochem., Soc., 140 (1993), 1526). and Fuller et al. (TF Fuller, M. Doyle and J. Newman, J. Electrochem., Soc., 141 (1994), 1 ; TF Fuller, M. Doyle and J. Newman, J. Electrochem. Soc. 141 (1994), 982) expected. The parameters used are shown in Table 1. layer parameters anode separator cathode Thickness (μm) 55 25 50 porosity 0.34 0.4 0.29 Capacity (mAh / cm ² ) 30 30 battery cell External heat transfer coefficient (W / m ² - K) 80 Separator surface (cm ² ) 700 cell surface 42 Heat capacity (J / kg - K) 900 Table 1: Parameters for the calculation of the simulation

The results of the simulation are in the figures 2 to 5 summarized. In 2 and 3 is the released heat output shown for an external circuit model ( 2 ) and without external circuit ( 3 ). It turns out that the connection of an external circuit leads to a reduction in the heat output released at the location of the short circuit. As in 4 This also leads to a reduced maximum temperature peak at the location of the short circuit. The released heat output of the whole battery cell increases through the external circuit, but is now distributed over the entire battery cell and less concentrated at the location of the short circuit. The connection of an external circuit also significantly reduces the absolute discharge time of the battery cell. Ie. the absolute amount of energy released in the battery cell is reduced (see 5 , Internal only curve), which in turn leads to a reduced increase in temperature at the location of the short circuit. 5 also shows that the absolute energy evolution curve for a cell with an external circuit has a steeper slope. Since the absolute energy of the two cells is constant and equal, the absolute discharge time is significantly reduced for a battery cell with an external circuit.

All in all leads the connection of an external circuit to a Reduction of the absolute discharge time and a reduction of the absolute temperature peak at the location of the short circuit. The heat development is from a local place of short circuit now to the entire Cell and the external circuit distributed. The danger of another Damage or endangerment of the system and the Environment by the short circuit is thus reduced.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited non-patent literature

• Doyle et al. Doyle, TF Fuller and J. Newman, J. Electrochem., Soc., 140: 1526 (1993)). [0027]
• Fuller et al. (TF Fuller, M. Doyle and J. Newman, J. Electrochem., Soc.141 (1994), 1 [0027]
• TF Fuller, M. Doyle and J. Newman, J. Electrochem. Soc. 141 (1994), 982) [0027]

Claims (10)

Battery system comprising: a) a battery with one or more cells; b) a measuring and control unit, the temperature and / or the voltage of individual, several or all battery cells determined continuously or periodically; c) an external circuit that connects to the poles of the battery one or more switches is electrically conductively connected, so that power from a battery post via the external circuit can flow to the other battery pole; the control unit the position of the switch or switches such that, when exceeded a predetermined heat output and / or exceeded a predetermined voltage drop rate, the external circuit is conductively connected to the battery poles. Battery system according to claim 1, characterized the battery has at least one lithium-ion cell. Battery system according to one of the preceding claims, characterized in that for the predetermined Heat output and / or voltage reduction rate values selected who are in a short circuit, but not during one Normal operation or charging the used battery occur. Battery system according to one of the preceding claims, characterized in that the external circuit is a resistor Re, which is lower than the resistance Rs of a standardized Short circuit for a battery of the same type and the same Dimensioning like the battery used in the battery system. Battery system according to one of the preceding claims, characterized in that the external circuit no further having electrical consumers. Battery system according to one of the preceding claims, characterized in that the external circuit of the battery isolated present. Battery system according to one of the preceding claims, characterized in that the external circuit at least partially is designed cooled. Battery system according to claim 7, characterized in that that the external circuit is air-cooled, liquid-cooled and / or one or more latent heat storage is cooled. Consumers with a battery system after one of the Claims 1 to 8. Consumer according to claim 9, wherein the consumer a vehicle is.