DE102010020294A1 - Rechargeable electrical energy storage unit for supplying electrical power to e.g. starter in motor car, has lithium ion accumulator and reverse polarity protection circuitry, which are accommodated in housing - Google Patents

Abstract

The unit (10) has a lithium ion accumulator (14) e.g. starter accumulator and traction accumulator, and a reverse polarity protection circuitry (24), which are accommodated in a housing (12). The circuitry comprises a switching element e.g. fuse (20), safety fuse and electrical controllable shift member, which is arranged in series with the accumulator. The shift member is designed as a FET power transistor or a relay. The circuitry comprises a diode (22) and a resistor, which are arranged in parallel connection with the accumulator to bypass current in the switching element.

Description

The present invention relates to a rechargeable electrical energy storage unit according to the preamble of claim 1, and to a use of such an energy storage unit.

Such energy storage units are required, for example, for vehicles (eg motor vehicles for road traffic) in order to provide an electrical energy source that is always available for vehicle operation.

In conventional vehicles can thus z. As the starter, the ignition system, the headlights and other power consumers are supplied with electrical energy. As long as the combustion engine is running at a sufficiently high speed, the electrical energy supplied by the electrical generator is available. When the engine is at a standstill (eg when parking) or when starting, however, an energy source independent of the internal combustion engine or an energy store is required.

In principle, different sources of electricity would be suitable for this purpose, but their use partly precludes technical or economic reasons. Of the different types of accumulators (eg lead, nickel-cadmium, nickel-metal hydride, nickel-zinc, lithium-ion accumulators), the lead-acid battery has become popular due to its favorable price and long experience with the Technology and satisfactory life as a starter battery for motor vehicles enforced. Also in many other areas of small traction, such as lifts, wheelchairs wheelchairs, caravans, cleaning machines, etc., the lead-acid battery is widely used.

With the development of new battery technologies, however, there are now more and more alternatives to replace the well-established but technologically far superior lead-acid battery.

With the new accumulator technologies, in particular z. As the lithium-ion technology, can be achieved advantageously high volumetric and gravimetric energy densities.

In the electrical power supply of DC powered electrical equipment is often called a "reverse polarity protection" is provided to prevent connection of the power supply with the wrong polarity (reverse polarity) and / or to limit or prevent damage caused by a reverse polarity.

It is known that usually the protection of electronic devices that are supplied with the DC voltage at the supply input of these devices. Reverse polarity protection circuits are present in many electrical DC consumers, but also in electricity suppliers, such. Chargers and UPS systems. So is an electronic reverse polarity z. B. already integrated in many battery chargers at the output of the charger. Thus, the output electronics of the charger should be protected to prevent damage to the electronics of the charger in case of accidentally wrong (wrong polarity) connecting the charger to the battery.

All known circuits for reverse polarity protection in a power supply from a battery or when charging a battery based on the protection of the electronics (the electrical consumer or the battery charger), however, the protection does not relate to the battery itself.

Such "battery polarity reversal protection", which protects the battery from damage in the case of a reverse polarity connected battery charger, has hitherto not been considered necessary in the established lead-acid batteries for reasons explained below.

In a polarity reversal of the lead-acid battery to the consumer usually speaks of the "consumer protection", ie z. B. a polarity reversal protection circuit that is integrated in the consumer.

When a polarity reversal of the lead-acid battery to a charger usually speaks in the charger integrated reverse polarity protection.

If two lead-acid batteries are connected in reverse polarity (eg jump start), high currents will flow through the battery, but due to the high specific heat capacity of the lead-acid battery, they will not overheat the battery to lead. The result of the polarity reversal of the battery can be different. If the current-carrying diverting elements are designed to be correspondingly solid, the battery temperature rises to a limited extent until the energy is exhausted relatively quickly and the battery has converted all the chemical energy via the electrical energy and then into thermal energy. If the diverting elements (internal / external) are undersized, overheating of the diverting elements, associated with possible damage to these elements, or melting of the connecting cables (jumper cables) occurs.

Even if there were an overheating of the lead-acid battery, it would take a longer time to seriously damage the battery Continuous massive tracking of the energy necessary, since the battery itself does not exotherm (heat dissipation) reacts, even with strong warming. That is, no additional energy is supplied from the active reaction materials contained in the lead-acid battery. Therefore, monitoring of the battery (eg, battery of a vehicle such as a starter battery) against reverse polarity for the purpose of protecting the battery has heretofore been totally unnecessary.

The present inventors have now recognized a problem associated with the imminent replacement of the lead-acid battery by new battery technologies, in particular, for. As the lithium-ion technology, considered and must be solved accordingly.

This problem is that such batteries would often be irreversibly damaged or even destroyed in the known "installation environments" with wrong polarity connection. This will be explained in more detail below using the example of the lithium-ion battery.

The problem concerns z. B. in particular the field of starter or small traction batteries, but also other applications such. B. Traction batteries of (pure) electric vehicles or hybrid vehicles (with a combination of internal combustion engine and electric motor).

• – Verwendung von alten Ladegeräten ohne oder mit fehlerhafter Verpolschutzelektronik und dabei verpolter Anschluss der Lithium-Ionen-Batterie an das Ladegerät
• – Verpolter Anschluss an eine Ladeeinrichtung in einem Fahrzeug (Bordnetz bzw. Lichtmaschine) beim Einbau der Batterie in das Fahrzeug
• – Verpolter Zusammenschluss von Batterien beim Fremdstart über Fremdstartkabel. Die bevorstehende Ablösung der Blei-Säure-Batterie durch modernere Batterietypen wie z. B. Lithium-Ionen-Batterien ist sicherlich durch eine Übergangsphase begleitet. Dabei kann es beispielsweise durchaus vorkommen, dass Fahrzeuge mit einer Lithium-Ionen-Anlasserbatterie Starthilfe durch Fahrzeuge mit Blei-Säure-Anlasserbatterie erhalten. Da die hier als ”Ladeeinrichtung” fungierende Blei-Säure-Batterie jedoch (aus den oben erläuterten Gründen) keinen Verpolschutz besitzt, fließt dann im Verpolungsfalle ein Kurzschlussstrom über beide Batterien.

As in the past with the lead acid battery it will happen also in the future that z. B. a starter battery lithium-ion base is inadvertently reversed polarity. Mainly the following scenarios are conceivable for polarity reversal of a lithium ion battery:

• - Use of old chargers without or with incorrect polarity reversal protection electronics and reverse polarity connection of the lithium-ion battery to the charger
• - Reverse connection to a charging device in a vehicle (electrical system or alternator) when installing the battery in the vehicle
• - Reverse polarity connection of batteries at the remote start over third party start cable. The upcoming replacement of the lead-acid battery by more modern types of batteries such. B. Lithium-ion batteries is certainly accompanied by a transitional phase. It may happen, for example, that vehicles with a lithium-ion starter battery get jump start by vehicles with lead-acid starter battery. However, since the lead-acid battery functioning here as "charging device" (for the reasons explained above) does not have polarity reversal protection, in the reverse polarity case, a short-circuit current flows over both batteries.

Similar to the lead-acid batteries flow in reverse polarity of the lithium-ion battery very high currents. The battery may be heated very much and the temperature increases much more than with the lead-acid battery, since the specific heat capacity of the lithium-ion battery is much lower and the energy density is much higher compared to lead-acid batteries. Battery (about factor 4 to 5). This overheating of the lithium-ion battery can lead to the thermally unstable state of the battery, so that active materials in decay can additionally release energy and it can come to the thermal runaway ("thermal runaway"). The battery generates more and more energy through an exothermic process, which is released to the environment. Excessive overheating due to heat buildup can ignite the combustible organic electrolytes. In addition, it leads to the disintegration of the electrolyte and gas formation, so that the possibly existing cell valves open (in cells with rigid housings) or the cells inflate.

Depending on the structure of the active reactants, the lithium ion-based battery is more or less sensitive to excessive overheating.

Most cathode materials in lithium ion cells decompose at temperatures above 200 ° C. The z. For example, commonly used nickel-cobalt-aluminum ("NCA") cathode material is relatively strong, followed by cobalt oxide. Manganese oxide and phosphate-based cathode materials still show the greatest stability. The high stability of even the delithiated crystal structure means that when the battery is briefly overcharged, oxygen and excess lithium are hardly released. Nevertheless, the organic electrolyte can burn.

Against this background, it is an object of the present invention to develop a rechargeable electric energy storage unit of the type mentioned in particular for vehicles (eg in the automotive sector) in such a way that damage to the electrical or electrochemical battery accommodated in the case of reverse polarity is avoided becomes.

According to the invention this object is achieved in that the energy storage unit further comprises a housed in the housing of the energy storage unit Verpolschutzschaltung.

The invention also housed in this case of the energy storage unit battery, such as electrochemical lithium-ion battery or the like, preferably has its own housing, hereinafter also referred to as "battery case" (in the strict sense). In this case the polarity reversal protection circuit is preferably outside of this "battery case" housed (but within a housing surrounding the battery case). An accommodation of the polarity reversal protection circuit within a (inner) "battery case" should not be excluded in principle within the scope of the invention.

The polarity reversal protection circuit can be configured such that, in the case of a charging device connected to the energy storage unit (eg vehicle electrical system or eg starting aid battery of another vehicle), it shuts off or at least bypasses the (short-circuit) current flowing through the electric battery limited.

The polarity reversal protection (passive or active) integrated into an electrical energy storage unit (eg containing a lithium-ion battery) in the form of an electrical or electronic circuit according to the present invention can effectively protect the battery in the field of polarity. This can z. B. the otherwise possibly resulting danger of a "thermal runaway" are banned. The protection of the battery from a loss of function by reversing has z. B. for a lithium-ion battery in so far a high economic importance, as their manufacturing costs compared to the cost of a lead-acid battery even in mass production at the time (2009) are typically higher by a factor of about 5-15. Due to the structure of the lithium-ion battery would be without the reverse polarity protection according to the invention in a polarity reversal irreversible decline in capacity up to a total loss of function of the lithium-ion battery often inevitable. With the invention, however, a simple and inexpensive polarity reversal protection can be integrated into the battery, without causing high additional costs. This advantageously eliminates the risk that a thermal runaway occurs in the case of a battery used for the energy storage unit in the case of a binding.

Therefore, according to one embodiment, for. B. provided that the electrochemical battery is a lithium-ion battery. The term lithium-ion battery is intended here also include the developments created on the basis of this technology (eg, lithium polymer, lithium titanate, "super charge ion", lithium manganese, lithium iron phosphate Battery etc.).

In one embodiment, it is provided that the polarity reversal protection circuit comprises a shutdown element arranged in series with the battery. This makes it possible in a simple manner to switch off the current flowing in the Verpolfall via the battery (short-circuit). To increase the reliability or creation of redundancy, it is conceivable to arrange a plurality of shutdown elements in this series circuit.

For the formation of such a shutdown element, there are many possibilities.

For example, the shutdown element can be designed as a fuse. This is understood to mean an element which is irreversibly destroyed in the polarity due to the associated particularly large current and in this case assumes a high-impedance state. It can be z. B. to act a fuse in the strict sense, ie a sheathed or ungehäustes, at a well-defined current load melting metallic pipe section. In general, however, other fuses within the meaning of the invention are conceivable.

If a fuse is used, it is provided according to a particularly preferred development that the housing of the energy storage unit is designed so that a simple (in particular, for example, no tools requiring) replacement of a defective (destroyed) fuse is enabled.

In another embodiment, the shutdown element is designed as a self-resetting fuse. Like a normal fuse, the self-resetting fuse transitions into a high-resistance state when a well-defined current load is exceeded, so that the current flow at least substantially comes to a standstill. Unlike a conventional fuse, however, the self-resetting fuse is not destroyed in this case, but has the ability to return to the (low-impedance) initial state after a certain period of time.

Such self-resetting fuses are known as such, so that can be used in the context of the present invention advantageously in particular to these known embodiments. Suitable fuses are commercially available from different manufacturers, for example under the brand names "PolySwitch", "Multifuse", "Polyfuse" or "Everfuse".

Such self-resetting fuses are usually designed as a "PTC thermistor" d. H. as an element whose electrical resistance increases at high temperatures. Particularly suitable for the invention are PTC thermistors, the electrical resistance increases substantially jumpwise when exceeding a predetermined limit temperature.

Furthermore, the shutdown as an electrically controllable switching element, for. B. as a relay or a transistor (eg, bipolar transistor or FET).

In this case, it is provided according to a development that the polarity reversal protection circuit further comprises a circuit part for detecting a Verpolfalles and for driving the switching element. Since the polarity reversal protection circuit is accommodated in the housing of the energy storage unit, the electrical battery also accommodated in the housing can advantageously be used for the electrical supply of said circuit part. If the circuit part is to be supplied with a voltage of a value which deviates from the value of the already existing battery voltage, a corresponding voltage adjustment can take place via a DC / DC converter device, which converts the battery voltage to a voltage value suitable for supplying the circuit part. It should be remembered, however, that when a trap occurs, the battery voltage quickly collapses and then changes to negative (reverse polarity). However, this problem can z. Example, by means of suitable design of the DC / DC converter or a combination of several DC / DC converters, as described below under an exemplary embodiment, are solved.

Alternatively or in addition to the arrangement of a shutdown element in series with the battery, it is provided according to an embodiment that the polarity reversal protection circuit comprises a bridging device arranged in parallel with the battery for current diversion in Verpolfall. The bridging device can, for. B. be designed so that in Verpolfall at least 30%, in particular at least 50% of the current flowing through the energy storage unit (short-circuit) current over the lock-up device and thus flow past the battery. This reduces the current load of the battery accordingly.

In an embodiment it is provided that the bridging device comprises at least one diode. In the simplest case, the bridging device consists of a diode which is arranged in the reverse direction parallel to the battery. In Verpolfall then flows from the relevant charging device (eg vehicle electrical system) of the energy storage unit impressed current at least appreciably or even substantially completely on this diode and not on the battery.

Instead of such a diode, a plurality of diodes may be connected in parallel and / or series connected to each other and arranged as a diode arrangement in total in parallel with the battery. This can z. B. in a simple way the current carrying capacity of the bridging device formed therewith be increased.

In one embodiment, the bridging device is designed so that it permanently withstand the load caused by the Verpolfall, so it is not destroyed. However, it should not be ruled out that the lock-up device, similar to the fuse already described above, will be operationally destroyed in the coil, in which case, as with the above-described fuses, easy access to the replacement of the bridging element (s) should be provided. The benefit of such a one-time bypass device is that the (short-circuit) current is at least partially kept away from the battery for at least a short time, so that for a response of an additionally provided protective mechanism such. As the above-mentioned shutdown (in series with the battery), or a Verpolschutzschaltung in the charger, more time remains.

In general, it is sufficient if the polarity reversal protection circuit has either at least one shut-off element arranged in series with the battery or a bridging device arranged in parallel to the battery. Alternatively, however, the polarity reversal protection circuit can also have both the at least one switch-off element and the bridging device.

A particularly preferred use of the energy storage unit is its use for a vehicle, for example as a starter battery of a conventional motor vehicle or as a traction battery of an electric vehicle or hybrid vehicle.

For traction batteries of electric and hybrid vehicles, although often a "reverse polarity protection" is provided on the battery unit to be installed, which reliably prevents special design of the battery terminal poles on the one hand and the connection cable terminals, a vergolten installation of the battery. However, this is usually not the case for starter and traction batteries since their terminals, i. H. the battery posts projecting from the housing are very strongly standardized (eg "cone pole" for 85-90% of the batteries as standard) and therefore do not allow any additional mechanical shaping of the connections to achieve mechanical reverse polarity protection.

The invention will be further described by means of embodiments with reference to the accompanying drawings. They show:

1 an energy storage unit according to a first embodiment,

2 an energy storage unit according to a further embodiment,

3 an energy storage unit according to a further embodiment,

4 an energy storage unit according to a further embodiment,

5 an energy storage unit according to another embodiment, and

6 an energy storage unit according to another embodiment.

1 shows a rechargeable electrical energy storage unit 10 , which in the illustrated embodiment z. B. is intended for installation in a motor vehicle to provide the so-called starter battery.

The energy storage unit 10 has a housing 12 , which is formed in practice, for example, approximately cuboid and in which an electric battery 14 is housed from a plurality of interconnected battery cells. Deviating from the simplified representation according to 1 For example, the battery cells can be interconnected in a combined series / parallel circuit.

The battery 14 is in the illustrated embodiment, a lithium-ion battery with a correspondingly advantageous high volumetric and gravimetric energy density.

A first (negative) connection of the battery 14 is with a first (negative), out of the case 12 outstanding pole 16 connected, and a second (positive) connection of the battery 14 is with a second (positive), out of the case 12 outstanding pole 18 connected, wherein in the connecting line between the positive battery terminal and the positive pole 18 a fuse 20 (in series with the battery 14 ) is arranged. Further, a diode 22 in parallel (antiparallel) to the battery 14 arranged.

In this embodiment form the fuse 20 and the diode 22 one in the housing 12 housed passive polarity reversal protection circuit 24 which the battery 14 in the case of an inadvertently compensated connection of the energy storage unit 10 to the relevant vehicle electrical system or a charging device protects.

Although this is shown in the schematic representation of 1 not explicitly shown, so does the battery 14 as such in practice expediently own a "battery case", in which the mandatory for the battery function required "electrochemical components" are housed. Depending on the battery type, this may be z. B. electrolytes (eg., Liquid or gel-like to solid (eg, films, membranes, etc.), electrolyte electrodes, separators, etc., and line connections for interconnecting multiple "battery cells." Within such a battery case can about The same applies to the polarity reversal protection circuit according to the invention, the components of which can thus be accommodated inside and / or outside the battery housing 24 at least within the case 12 but preferably housed outside a "battery case" optionally arranged therein.

To illustrate the function of the polarity reversal protection circuit 24 is in the right part of the 1 one polarity reversed to the energy storage unit 10 connected charging voltage source 26 symbolizes which at the battery poles 16 . 18 the battery 14 a suitable for charging their voltage U applies, but this as shown with the wrong polarity.

The in this "Verpolfall" about the energy storage unit 10 flowing short-circuit current can in the illustrated embodiment, the battery 14 not damaging, because, depending on the design of the diode 22 (with regard to the internal resistance of the battery 14 ), a significant proportion of this current across the diode 22 and thus on the battery 14 passed by. Regardless of this, an excessive current in the coil will be through the battery 14 after a short while, to stop the fuse 22 blows.

The fuse 20 is dimensioned in terms of their current carrying capacity that at an energy extraction from the energy storage unit 10 maximum discharge current (eg during starting) does not yet cause the fuse to blow 20 leads.

For the design of the diode 22 There are different possibilities. For example, it can be provided that this diode 22 is destroyed in the trap by the high current load. In this case, the diode uses 22 to protect the battery 14 in the period from the beginning of the Verpolfalles until their destruction or until the melting of the fuse 20 , However, it is also possible to use the diode 22 be designed for a permanent resistance to this current load.

An advantage of the illustrated embodiment is that during a discharging process (eg starting operation) the polarity reversal protection circuit 24 does not cause a power-consuming voltage drop. Depending on the specific design of the protective elements 20 . 22 However, after a postponement a replacement of these elements may be required. Therefore, should be on the case 12 an access to the replacement of the blown fuse 20 (and possibly the destroyed diode 22 ) to be available. Preference is given to the housing 12 one or more receiving spaces provided for these elements, to which a tool-free access can take place (eg., By the respective elements in a freely accessible from the outside recess (indentation) of the housing 12 be arranged or by such a simple access is created after releasing a receiving space cover or the like).

Although in the in 1 illustrated embodiment, both a "shutdown" (fuse 20 ) as well as a "bridging device" (Diode 22 ) is provided, the reverse polarity protection would also work if either the shutdown element or the bridging device would be omitted.

In the following description of further embodiments, the same reference numerals are used for equivalent components, each supplemented by a small letter to distinguish the embodiment. In this case, essentially only the differences from the embodiment (s) already described are discussed and, moreover, reference is hereby explicitly made to the description of previous exemplary embodiments.

2 shows a further embodiment of an energy storage unit 10a in which a polarity reversal protection circuit 24a again from a series connection with a battery 14a arranged fuse 20a and a diode connected in parallel 22a is formed. In contrast to the embodiment according to 1 is the fuse 20a however, in series with the parallel arrangement of the battery 14a and the diode 22a arranged so that in the case of polarity the sum of the over the battery 14a and the diode connected in parallel 22a flowing short-circuit current through the fuse 20a flows.

With the in 2 hatched area around the diode 22a should be symbolized that instead of a single diode and a "diode array" consisting of several interconnected (parallel and / or serial) may be provided at this point.

An advantage over the embodiment according to 1 is that the fuse 20a thus also as protection for the diode 22a Can serve (or diode array), as in the case of burning through the fuse 20a also by the diode 22a flowing electricity comes to a standstill.

In 2 dashed lines are still two other possible locations of fuses 20a ' and 20a '' on which fuses alternatively or in addition to the fuse 20a can be arranged.

3 shows a further embodiment of an energy storage unit 10b with a polarity reversal protection circuit 24b , The circuit 24b corresponds largely to the example in accordance 1 used protection circuit 24 , but with the difference that instead of a fuse a self-resetting fuse 28b is used.

A self-resetting fuse (eg, "PolySwitch" fuse element with monolithic structure) responds in circuits to overcurrent similar to a normal fuse. Unlike a normal backup, which does not reset itself and is not reusable, the self-resetting fuse resets itself after the power has been interrupted. Thus, a replacement of the backup is no longer necessary. The fuse can z. B. contain a solid state material which is filled with elemental carbon and thus conductive polymer. The electrical resistance of this material increases with increasing temperature. The current flow through the element causes Joule's heat, which leads to an increase in the temperature and thus the resistance. If the current exceeds a certain value, Joule heat transfers the element to a high resistance state (i.e., the element switches). In this condition, the voltage drop across the fuse increases and the current reaches a value far below the normal state. When designing, it must also be taken into account here that the fuse does not cause tripping in the case of operational starting currents.

The position of the self-resetting fuse 28b could be different too 3 can be selected, for example, as in 4 shown.

4 shows a further embodiment of an energy storage unit 10c with a polarity reversal protection circuit 24c like the example according to 3 from one in series with a battery 14c arranged self-resetting fuse 28c and a diode or diode array arranged in parallel 22c is formed. In contrast to the embodiment according to 3 is the fuse 28a however, in series with the parallel arrangement of the battery 14c and the diode 22c arranged so that in the case of polarity the sum of the over the battery 14c and the diode connected in parallel 22c flowing short-circuit current through the fuse 28c flows.

In 4 dashed lines are two more possible locations of fuses 28c ' and 28c '' on which fuses alternatively or in addition to the fuse 28c can be arranged.

5 shows a further embodiment of an energy storage unit 10d with a polarity reversal protection circuit 24d , Here, as a variant of the protective circuits according to the 1 to 4 provided as a bridging device instead of a diode (or diode array), a transistor protection circuit. This includes a transistor 30e , which normally locks (without polarity reversal) and is turned on in the Verpolfall. For detecting the Verpolfalles and for driving the transistor 30d is the base terminal of the transistor 30d as shown via a resistor 32d with the collector terminal of the transistor 30d (or the negative connection) of the battery 14d connected.

The polarity reversal protection circuit formed by the transistor circuit 24d is in this example thus an active circuit for the implementation of the bridging device.

Deviating from the illustration in 5 In addition, at least one switch-off element could be connected in series with the battery 14d be arranged (for example, a fuse and / or self-resetting fuse).

6 shows a further embodiment of an energy storage unit 10e with an active polarity reversal protection circuit 24e ,

The polarity reversal protection circuit 24e includes a DC / DC converter 34e , a detection and control circuit 36e , a switching transistor 38e and a current measuring resistor (shunt) 40e ,

The current measuring resistor 40e is in series with a battery 14e arranged. The detection and control circuit 36e is used to measure the resistance 40e decreasing voltage, which is representative of the over the battery 14e flowing electricity is. A Verpolfall is easily recognizable by the fact that the resistance 40e measured voltage drop assumes a particularly large value (and has the corresponding polarity). Upon detection of a Verpolfalles switches the detection and control circuit 36e the associated switching transistor 38e off, so that the short-circuit current comes to a standstill and the battery 14e is protected. The switching transistor 38e This is in series with the battery 14e arranged and thus serves as a shutdown.

For the electrical supply of the detection and control circuit 36e this is with the output of the DC / DC converter 34e connected, which input side with the battery 14e , ie their negative and positive battery terminals are connected.

It should be noted that in polarity the polarity of the input of the illustrated DC / DC converter 34e applied voltage reverses. Nevertheless, to ensure the power supply of the active monitoring, even with negative input voltage of the converter, it makes sense, the converter z. B. as an insulating converter, which can generate a positive output voltage from a negative input voltage. For example, a transformer used in the DC / DC converter can ensure galvanic isolation between input and output, with the ground terminal of the input being assigned to the positive output terminal, thus producing a negative output voltage to the negative output terminal, that is, the DC / DC converter acts as a polarity or voltage changer.

Alternatively, two DC / DC converters, each with one output, could also be interconnected in such a way that one converter supplies a positive output voltage when the input voltage is positive, and the other DC / DC converter is connected as a voltage changer. The connection point of the two transducer outputs may be assigned a ground potential, whereby the negative output of the second transducer provides a negative voltage relative to the ground connected positive output.

Regardless of the specific embodiment of the DC / DC converter, the polarity reversal protection circuit could 24e differing from the illustrated embodiment also include an energy storage (eg, capacitor or the like), which in normal operation of the energy storage unit 10e is charged or charged, and from which in Verpolfall then the further supply of the detection and control circuit 36e he follows. In the presence of a turn-off element, such as the illustrated switching transistor 38e , This further supply from the energy storage is advantageous only for a very short period of time required because by switching off the shutdown element (here: switching transistor 38e ) immediately returns to normal battery voltage 14e is available at the input of the relevant DC / DC converter (or directly on the energy storage such as capacitor). For measuring the battery current by measuring the voltage drop across the current measuring resistor 40e can the detection and control circuit 36e z. B. comprise a comparator, which compares this voltage drop with a predetermined reference value and when exceeding the reference value by the voltage drop, the described shutdown of the switching transistor 38e triggers. Such a comparator can in a conventional manner z. B. be implemented by means of an operational amplifier.

Instead of the switching transistor 38e (here: FET power transistor) could z. B. a bipolar transistor or other suitable (electrically controllable) switching element can be used (eg, a relay).

To increase the reliability of the polarity reversal protection circuits in the embodiments of the 5 and 6 For example, a further cut-off element could be arranged in series with the battery, for example a fuse or a self-resetting fuse as already described above.

In an active Verpolschutzschaltung, which in particular has a functioning in Verpolfall power supply, such. B. in the example according to 6 provided, according to a very advantageous development additionally monitoring of other operating parameters of the relevant energy storage unit, in particular the battery contained therein, take place. As another operating parameter z. Example, a temperature of the battery to be monitored, for example, to cause a shutdown of the battery current even when exceeding a predetermined maximum temperature.

The invention may, for. B. for use as integrated in an energy storage installation unit polarity reversal protection for starter batteries in vehicles with internal combustion engine but also in particular as integrated polarity reversal protection in lithium-ion batteries in small traction vehicles in industrial use (cleaning vehicles, wheelchairs wheelchairs, caravans).

Claims (10)

Rechargeable electrical energy storage unit ( 10 ) with one in a housing ( 12 ) accommodated battery ( 14 ), characterized in that the energy storage unit ( 10 ) further in the housing ( 12 ) accommodated polarity reversal protection circuit ( 24 ) having. Energy storage unit according to claim 1, wherein the battery ( 14 ) is a lithium-ion battery. Energy storage unit according to one of the preceding claims, wherein the polarity reversal protection circuit ( 24 ) in series with the battery ( 14 ) arranged shutdown element ( 20 . 28 . 38 ). Energy storage unit according to claim 3, wherein the shutdown element ( 20 . 28 . 38 ) as a fuse ( 20 ) is trained. Energy storage unit according to claim 3, wherein the shutdown element ( 20 . 28 . 38 ) as a self-resetting fuse ( 28 ) is trained. Energy storage unit according to claim 3, wherein the shutdown element ( 20 . 28 . 38 ) as electrically controllable switching element ( 38 ) is trained. Energy storage unit according to claim 6, wherein the polarity reversal protection circuit ( 24 ) a circuit part ( 36 ) for detecting a Verpolfalles and for driving the switching element ( 38 ). Energy storage unit according to one of the preceding claims, wherein the polarity reversal protection circuit ( 24 ) one in parallel with the battery ( 14 ) arranged bridging device ( 22 . 32 ) for power diversion in Verpolfall includes. Energy storage unit according to claim 8, wherein the bridging device ( 22 . 32 ) at least one diode ( 22 ). Use of an energy storage unit ( 10 ) according to one of the preceding claims for a vehicle.

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