CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Entry of PCT/EP2018/062198, filed May 11, 2018, entitled “ENERGY STORAGE SYSTEM FOR A VEHICLE,” which claims priority to German Patent Application 10 2017 110 218.3, filed Nov. 5, 2017, entitled “ENERGY STORAGE SYSTEM FOR A VEHICLE”.

The present application relates to an energy storage system for a vehicle, in particular to a starter battery for a vehicle.

As a general rule, 12 volt lead-acid batteries are usually used as starter batteries for vehicles. These are designed to start a drive unit in the form of an internal combustion engine and to maintain the function of the onboard electrical system; i.e. the starter battery provides the high current required when starting the vehicle. While the vehicle is traveling, the starter battery can furthermore supply voltage to an onboard electrical system of the vehicle and be charged.

The starter battery usually has a multiplicity of battery cells that are connected electrically together. However, the individual battery cells are individually sealed off from their surroundings and other battery cells for example via a cell housing.

On account of the electrochemical reactions that occur in the starter battery during a charging or overcharging process, a gas mixture made up at least of hydrogen, oxygen and carbon dioxide typically collects in an upper cell space or gas space. In a valve-regulated lead-acid battery, a considerable amount of oxygen can diffuse in the direction of negative electrode plates during operation and be subject to a recombination reaction forming water there; however, hydrogen and carbon dioxide cannot be so easily removed again.

Since the gas pressure in the gas space increases constantly, for safety reasons, each battery cell is conventionally equipped with a (dedicated) one-way valve, which opens whenever the gas pressure in the upper region of the cell space reaches a predetermined or predeterminable opening pressure.

After a particular quantity of gas has escaped, the gas pressure in the battery cell drops and the vent valve closes as soon as the gas pressure reaches a predetermined or predeterminable closing value.

It is assumed here that all battery cells have an identical or similar gas pressure and an identical or similar gas composition in their upper region. However, in practice, it can be established that the individual vent valves exhibit a significant variation in their manners of operation.

First, the actual opening and closing pressures of the vent valves often do not coincide with the predetermined or predeterminable values. Furthermore, the actual opening- and closing-pressure values change during the operation of the battery or during the lifetime of the battery, specifically as a result of aging of the vent valves, in particular under difficult and demanding conditions, for example with high temperatures, overcharging, and/or the occurrence of acid vapor.

Here, particular vent valves can even remain “virtually open” for a long time, resulting in a slower recombination process and greater water loss.

In short, such conventional energy storage systems thus have the drawback that the individual battery cells, at least after a certain operating time, no longer have the same or a similar gas pressure and an identical or similar gas composition, with the result that the performance of the individual battery cells can also worsen or change.

Moreover, as a result of such a configuration of a starter battery, it is even possible for individual cells to fail completely, with the result that, in the worst case, the starter battery is no longer capable of starting the vehicle or of supplying the onboard electrical system with energy.

Since, in such energy storage systems, the individual battery cells are configured such as to be separated from one another and sealed, such battery cells have to be tested for their cell-to-cell gas tightness, in particular before they are used.

Therefore, the invention is based on the object of providing an energy storage system that does not have the limitations of the prior art and can furthermore be produced more easily, quickly and cost-effectively. In addition, the energy storage system is intended to ensure increased quality and safety.

With regard to the energy storage system, the object on which the invention is based is achieved by the subject matter of independent claim1. Further embodiments are set out in the dependent claims.

Therefore, according to the invention, an energy storage system for a vehicle, in particular a starter battery for a vehicle, is specified. The energy storage system has a multiplicity of energy storage cells for providing and/or storing electrical energy, and a housing that has a multiplicity of wall elements that bound an interior of the housing. In this case, the housing is configured to accommodate the multiplicity of energy storage cells in the interior of the housing. Furthermore, a multiplicity of dividing walls for subdividing the interior of the housing into a multiplicity of chambers are arranged in the interior of the housing. Each chamber is moreover configured to accommodate an energy storage cell, wherein a fluidic connection is formed between the individual chambers. In this case, a vent valve is arranged on one of the wall elements, preferably a cover element, of the housing in each case in a region assigned to a corresponding chamber, wherein at least one of the vent valves is an active vent valve and the rest of the vent valves are blind plugs.

The advantages of the invention are obvious. Firstly, product and production costs can be lowered, specifically, for the one part, by reducing the number of active vent valves that are required, and, for the other part, in that conventional housings can be developed or retrofitted easily by replacing the conventional (sealed) dividing walls with the dividing walls according to the invention, which are configured to allow a fluidic connection between the individual chambers, specifically without it being necessary to provide new production tools for the housing.

The reduction in the number of active vent valves is also accompanied by quicker manufacture of the energy storage system, since the production time for a vent valve, which is relatively complicated compared with a blind plug, is shorter, this at the same time also lowering the production costs.

Furthermore, time and costs can be saved because it is possible to dispense with the test for cell-to-cell tightness.

It is also possible, after the electrolyte has been fed to the energy storage cells, for all the energy storage cells to be evacuated equally. As a result, only one vacuum pump is now required rather—as previously conventional—one for each chamber, with the result that the production complexity can be kept low.

Furthermore, the battery quality can be improved, specifically in that, the formation of the fluidic connection between the individual chambers ensures that the individual energy storage cells are vented equally and thus at least substantially no quality differences can form in the individual energy storage cells on account of different gas pressures and/or gas compositions of the individual energy storage cells.

Moreover, it is also possible for the inspection costs and the inspection work to advantageously be reduced, specifically in that, for safety purposes, it is now necessary to check the gas pressure, the gas composition and/or the gas flow of only one space, rather than the gas pressure, the gas composition and/or the gas flow of each individual energy storage cell as in conventional energy storage systems. Therefore, safety issues related to gas management can be handled better when only one active vent valve or two active vent valves are present compared with when—as in conventional energy storage systems—each energy storage cell has a dedicated vent valve.

These and further advantageous effects can also be found in the dependent claims.

According to one further aspect of the invention, at least one of the vent valves is in the form of a blind plug.

According to one further aspect of the invention, exactly one active vent valve is arranged on the one wall element, in particular on the cover element, of the housing, specifically preferably such that the active vent valve is assigned to a chamber that is arranged in a central region of the interior of the housing.

According to one further aspect of the invention, two active vent valves are arranged on the one wall element, in particular on the cover element, of the housing, specifically preferably such that the two active vent valves are assigned to two chambers that are separated from one another via at least one (further) chamber that is assigned a blind plug.

According to one further aspect of the invention, each dividing wall has at least one opening for forming the fluidic connection between the individual chambers.

According to one further aspect of the invention, at least one of the multiplicity of dividing walls, in particular all of the dividing walls, has/have in each case exactly one opening in an upper region of the particular dividing wall.

According to one further aspect of the invention, the one opening per dividing wall is arranged such that at least two adjacent dividing walls have the opening in an offset manner, in particular in an alternately offset manner, specifically preferably in an upper end region or in one of two upper corner regions of the dividing walls.

According to one further aspect of the invention, at least one dividing wall, in particular all of the dividing walls, has/have an opening in an upper, central region of the particular dividing wall.

According to one further aspect of the invention, at least one of the multiplicity of dividing walls, in particular all of the dividing walls, has/have in each case exactly two openings in an upper region of the particular dividing wall, wherein the two openings are preferably arranged in each case in two upper end regions or in two upper corner regions of the corresponding dividing wall.

According to one further aspect of the invention, a membrane is formed in at least one of the openings, in particular in each opening.

According to one further aspect of the invention, the active vent valve is in the form of a one-way valve with a predetermined or predeterminable venting pressure, wherein the one-way valve is in this case integrated preferably into a vent plug.

According to one further aspect of the invention, the blind plugs are in the form of vent plugs, which are configured to seal off the interior of the housing.

According to one further aspect of the invention, the energy storage system is a lead-acid battery.

According to one further aspect of the invention, the energy storage system is in the form of a valve-regulated lead-acid battery, in particular of a valve-regulated absorbent glass mat (AGM) lead-acid battery.

The invention is described in more detail below, including with regard to further features and advantages, on the basis of the description of embodiments with reference to the accompanying drawings.

