WO2017134346A1

WO2017134346A1 - Method for maintaining a battery

Info

Publication number: WO2017134346A1
Application number: PCT/FI2017/050059
Authority: WO
Inventors: Rauno Turunen; Juho TYSTER
Original assignee: Kemppi Oy
Priority date: 2016-02-03
Filing date: 2017-02-03
Publication date: 2017-08-10
Also published as: FI20165076A

Abstract

The invention is directed to a method for maintaining a battery, method comprising the steps of detecting a magnetic field between a battery powered device (10) and a battery charger(20), establishing communication between a wireless battery charger (20) and the battery powered device (10) to determine whether the battery powered device (10) is placed in the battery charger (20); and if communication between the wireless the battery charger (20) and the battery powered device(10) fails, indicating this to the user. The invention is also directed to a battery charger (20) comprising a primary coil (40) for inductive charging of a battery(110) of a battery powered device (10), a charger controller (60), means for forming a magnetic field (80) and means for communication (100) with a battery powered device (10).

Description

METHOD FOR MAINTAINING A BATTERY

FIELD OF THE INVENTION

The invention relates to wireless charging of batteries and optimization of lifetime of batteries and battery powered devices, and more particularly to a magnetic battery charger sensor and a charging logic of a battery with improved usability

BACKGROUND OF THE INVENTION

US 2005/0127878 A1 discloses a battery protection circuit including a safety circuit and an overpower circuit. The safety circuit monitors the voltage and current of at least one rechargeable cell within the battery pack, and disconnects the cell(s) from the external terminals of the battery pack when either the voltage becomes too high or low, or when excessive current is being drawn from the battery pack. The overpower circuit monitors the power being delivered to or sourced from the battery pack to the load. The overpower circuit actuates when the power exceeds a predetermined threshold, thereby simulating an overcurrent condition in the safety circuit. The overcurrent condition causes a disconnect means, like a transistor, to open, thereby disconnecting the cell(s) from the external terminals.; The battery protection circuit then latches in this disconnected state until a load is removed from the terminals of the battery pack.

US 201 1 /050000 A1 discloses a battery management system capable of safely disconnecting a charge/discharge current line from a battery pack in an over-charge condition is provided. The battery management system includes a charge/discharge relay including a relay switch coupled to a charge/discharge current path of a battery pack and a driving coil for driving the relay switch, a relay driving unit for controlling the driving coil, a motor control unit (MCU) for controlling the relay driving unit, the MCU being coupled to the relay driving unit, a switching device being coupled between the driving coil and the relay driving unit, and a switching control unit for controlling on/off operations of the switching device to control a current of the relay driving unit.

US 6184651 B1 discloses a contactless charging system wherein charging energy is transferred across an inductive coupler to charge a battery of a portable device, such as a two-way radio, cellular phone, paging device, or wireless communicator. The inductive coupler also provides a way for communicating at least one signal, such as to improve the charging process and the transfer of charging energy. Charging efficiency is improved by voltage regulation using feedback through the inductive coupler, or via a wireless RF link, and a controller in-circuit with the primary side of the inductive coupler. The controller may communicate information signals via inductive coupling, or via a wireless RF link, for communicating with other devices such as smart cards and microphones or for control or data transfer.

US 2005162125 A1 describes an integrated induction battery charge apparatus and an integrated induction charge battery. The integrated induction battery charge apparatus comprises a power supply for providing electric energy, a detection module to detect the charge battery and to generate a start signal when the charge battery is detected, an activation module, for receiving the start signal and turning on a power supply switch, and an induction module for transforming the electric energy to magnetic energy through electromagnetic induction. The activation module comprises as least one MOS-transistor, which is triggered and turned on by the activation signal to provide the required electric power for the induction module.

A problem with existing battery chargers and batteries is that if a battery powered device remains unused for a longer period of time i.e. the device is not charged for a longer period of time or the device is in the charger but the charger is not connected to the mains and thus not charging the battery, the batteries will slowly discharge which might lead to a situation wherein the charge of the battery falls below a critical point where they might be damaged from being under charged. If the charge of a battery falls below the critical point the battery cells are permanently damaged and battery capacity is lost.

Another problem is that a battery when not in use, will slowly discharge, and might after a long time in storage need be charged again before use.

A problem with some larger devices, such as welding devices is that when not in use for a longer period of time they are programmed to enter standby or alternatively hibernation in order to save power. A battery powered device should still be able to recognize when it is connected to a wireless charger even though being in hibernation. This has traditionally been solved by using a capacitive or other kind of RF-connection communicating with the charger in order to establish whether the device is in the charger or not. A problem with this solution is complexity which causes unreliability issues especially when the device is in a harsh EMC environment which are out of norms. Another problem with this solution is though that this is energy consuming and after a number of attempts might lead to a situation where the battery is discharged below the critical point and the battery is thus damaged.

In existing solutions, the charging process cannot be started from powerless state or without any active communication between the charger and the device to be charged. BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a magnetic battery charger and a charging logic so as to overcome the above problems or at least to alleviate the above disadvantages. Another object of the invention is to provide a magnetic battery charger that is easy to use and which will avoid any situations of misuse, even in a state when the charger is not coupled to the mains or the battery powered device is in hibernation, i.e. virtually powerless.

The objects of the invention are achieved by a method for maintaining a battery, comprising the steps of detecting a magnetic field between a battery powered device and a battery charger, establishing communication between a wireless battery charger and the battery powered device to determine whether the battery powered device is placed in the battery charger and starting a battery maintenance function upon receipt to the communication and if communication between the wireless the battery charger and the battery powered device fails, indicating this to the user and, a battery charger comprising a primary coil for inductive charging of a battery of a battery powered device, a charger controller, means for forming a magnetic field and means for communication with a battery powered device.

The preferred embodiments of the invention are disclosed in the dependent claims.

An advantage of magnetic battery charger sensor of the invention is that a magnetic battery charger sensor in a battery charged device automatically wirelessly detects that the device is placed in the charger without any further actions of the user, and automatically starts the battery maintenance function. The use of a magnetic charger sensor minimizes the power consumption in an idle state, e.g. when in storage.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

Figure 1 is shows a battery powered device;

Figure 2 is shows a battery powered device placed in a charger; and

Figure 3 is a flow chart of the process of switching from operation mode to the battery maintenance function;

DETAILED DESCRIPTION OF THE INVENTION

The following embodiments are exemplary. Although the specification may refer to "an", "one", or "some" embodiment(s), this does not necessarily mean that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may be combined to provide further embodiments.

In the following, features of the invention will be described with a simple example of a device architecture in which various embodiments of the invention may be implemented. Only elements relevant for illustrating the embodiments are described in detail.

The invention relates to a magnetic battery charger sensor. The invention also relates to a battery maintenance logic for maintaining a battery, which battery maintenance logic can be started from a powerless state.

According to the invention a battery charged device, such as a welding machine, or another power tool and a charger thereof comprise a magnetic sensor and a permanent magnet. When the battery powered device is placed in the charger, the magnetic sensor and the magnet form a connection by means of a magnetic field. This connection together with a controller is used to activate a maintenance function in the electronics of either the device or the charger, i.e. wherein it is determined whether the battery needs to be charged or not, based on signals given from both the controller of the device and that of the charger.

When a user places a device in a charger a magnetic field between a magnetic sensor and a magnet in the device and the charger forms a magnetic field. The magnetic field then activates a function in a control logics of the charger or optionally the device that will turn on the battery maintenance process.

Alternatively, a magnetic field is already present in the charger even before placing the device in the charger. This may e.g. be realized using passive magnets or the like.

No other action is needed from the user apart from placing the device in the charger. The maintenance is started automatically, no user-initiated commands have to be given or buttons have to be pressed.

No galvanic electric contact between the charger and the device is needed, neither is there any need for any mechanic protrusions or the like to activate the maintenance process. According to an embodiment of the invention a device to be charged may have at least three modes of operation: ON, STANDBY and HIBERNATION.

Here ON mode refers to a mode of operation, e.g. in case the device is a welding device ON mode equals a welding mode.

Here STANDBY is a power-saving mode in which the device is ready to be switched to ON mode due to a command from the user interface. Here HIBERNATION refers to a state of inactivity of most components of the device. When the battery voltage drops below a threshold, where normal STANDBY would no longer be safe for the battery integrity, e.g. 3 volts/cell in standby mode a controller of the device will detect this and set the device in a hibernation mode where all controllable functions are then turned off.

Figure 1 shows an exemplary structure of a battery powered device that may be powered by a charger according to the invention. The battery powered device 10 comprises a secondary coil 30, a controller 50 and a magnetic sensor and a magnet 70. The device also comprises a radio frequency transceiver or inductive loop 90 and a battery 1 10 as well as a secondary converter 120. The device may further comprise power electronics 140, a user interface 150, a welding cable 160 as well as a grounding cable 170 for a work piece.

Figure 2 shows an exemplary structure of the device of figure 1 placed in a battery charger according to an embodiment of the invention. The battery charger comprises a primary coil 40 a charger controller 60 a magnetic sensor and a magnet 80. The battery charger additionally comprises a radio frequency transceiver or inductive loop 100 for communicating with the battery powered device and a primary converter 130.

According to an embodiment of the invention inductive charging is used for charging the battery of the battery powered device. An induction coil, or primary coil in the charger is used to create an alternating electromagnetic field and a second induction coil or secondary coil in the battery powered device takes power from the electromagnetic field and converts it back into electric current in the secondary converter to charge the battery. The two induction coils in proximity combine to form an electrical transformer. A primary converter in the battery charger is used for converting an electric current to power for the primary coil in order to create the magnetic field.

According to a preferred embodiment controller 50 monitors the state of the battery cells during battery maintenance mode and if needed controls converter 120 to raise the voltage of the battery cells to a voltage level determined by the controller. Converter 120 receives the needed charging energy from secondary coil 30 and converts it to voltage suitable for the battery 1 10 and adjusts the current. If sensor 70 detects that controllers 50 and 60 are not in contact with each other and communication between communication means 90 and 100 is not detected, i.e. no charger is detected, the battery maintenance function is not continued. Controller 60 may also be used for controlling converter 130 to convert mains voltage AC into a suitable level for primary coil 40.

According to one embodiment the device may comprise a separate power supply between the sensor 70 and the controller for providing an excitation voltage for the controller 50. According to another embodiment controller 50 and sensor 70 may be on a single circuit board or realized as a single circuit instead of as separate components.

In hibernation mode, only sensor 70 of the device is in operation. When sensor 70 senses a magnetic field, it activates controller 50. When sensor 70 is in an ON-mode controller 50 attempts communication with controller 60 of the battery charger through communication means 90 and 100 of the device and the charger. If there is no response from controller

60 of the charger, controller 50 sets the device into operation mode after a delay. When controller 60 responds through communication means 90 and 100, the controller 50 of the device turns on the battery maintenance function. When in hibernation controller 50 is inactive and can be activated by sensor 70.

According to one embodiment of the invention the device may simultaneously be in an ON mode, i.e. in operation as using the battery maintenance function as the welding power is not taken directly from the mains voltage.

According to an embodiment of the invention a permanent magnet (70, 80) and a magnetic relay (70, 80) are used for creating and sensing the magnetic field when the device is placed in the charger. This enables a situation wherein the maintaining function of the battery may be started in a fully powerless state. I.e. no power is needed for the communication between the battery charger and the device in order to start the maintenance process. According to this embodiment the permanent magnet may be situated in either the charger or the battery powered device.

Figure 3 is a flow chart of an exemplary process of maintaining a battery of a battery powered device. When in operation (hibernation or standby or on) mode, if the magnetic sensor 70 of the battery charged device does not sense a magnetic field it stays in operation mode, meaning there is no attempt to establish RF-communication with the charger. If a magnetic field is detected by the sensor, the device will send out a RF-signal. If a reply is received a battery maintenance function is started. If no reply is received in a predetermined amount of time or alternatively number of attempts this will be indicated to the user and the device goes back to the operation mode where it was. The predetermined amount of time is from some minutes to half an hour. The charging logic according to the invention functions according to the following method: While in sleep mode, i.e. hibernation, the magnetic sensor relay is in an off mode. In other words, there is no attempt of communication between the battery powered device and the charger and the conclusion is that the device is not in the charger.

When the device is placed in the charger, a magnetic field is formed between the magnetic sensor and the magnet which turns on the magnetic sensor relay establishing that there is a communication between the charger and the battery powered device. When a connection is confirmed controller 50 starts the battery maintenance function. If the battery needs to be charged, charging is initiated, if no charging is needed the device stays in the operation mode where it was.

According to an embodiment, when the device is placed in the charger and it is established that there is a communication between the charger and the battery powered device, but the charger is not connected to the mains power, this will be indicated on the user interface of the device. This enables the user to connect the charger to the mains power and avoid situations where the user thinks that the batteries of the device are being charged when that is in fact not the case. The indication to the user may be made by Ul-message, i.e. a text or other alert appearing on the user interface of the device, by LED off / LED on, sound signal, or the like.

In a case where no communication can be established between the charger and the device, the device will go back to operation mode and a new attempt to establish a connection according to the previously described will take place after a predefined amount of time, for example a few minutes or half an hour. Alternatively, a number of attempts is used.

A situation may also arise where a communication is established due to a magnetic field detected while the device is not in the charger, e.g. if the device is placed on a magnetic table and the magnetic sensor is switched on. In this case the device will go back to its original operation mode since no communication with the charger could be established and a new attempt to establish a connection according to the previously described will take place after a predefined amount of time, for example a few minutes or half an hour. Alternatively, a number of attempts is used.

One advantage of the method and magnetic battery charging sensor according to the invention is that the construction of both the charger and the device remains simple. The charger itself doesn^'t include any charging logic. Another advantage is that there are no parts which are sensitive to being damaged due to impact or dirt. Optical identification for example is sensitive to dirt. Mechanical protrusions or buttons or switches are sensitive to impact, dirt and wear. A galvanic or electric coupling is another alternative but the problems are the same as listed before. Harsh out of norm EMC environment will also have effects which cannot be forecasted and that way may cause an unreliable connection.

A magnetic sensor enables a fully tight construction without any galvanic connections, and lacking mechanical or electrical connections which might be damaged or faulty due to dirt. At the same time a magnetic connection enables a construction without any buttons or commands needed from the user. The operation can thus be fully automatic without any other input from the user other than placing the device in the charger. Thus, is a scenario possible wherein a device may be in hibernation and is activated only when the magnetic sensor is activated.

A further advantage of the invention is that when in hibernation the invention enables the device to "wake up" or start when placed in the charger, since the "waking up" is a passive event, i.e. the presence of the magnetic field triggers a communication and wakes the device from hibernation. The communication between the device to be charged and the charger is not an active continuously occurring communication. In other words, neither the charger nor the device is continuously sending out communication attempts. This occurs only once a magnetic field is first detected.

Another advantage of the method and the magnetic battery charging sensor according to the invention is that it is very user friendly. The charger will always work as intended as the user does not have to switch it on or place the battery powered device very carefully in the charger. Furthermore, as it is indicated on the user interface of the battery charged device if the charger is not connected to the mains power or for some other reason is unable to start the battery maintenance function, situations do not arise where the user thinks that the battery powered device is being charged when it is not.

An advantage of the invention is that the magnetic battery charger sensor in a battery charged device automatically wirelessly detects that the device is placed in the charger, and automatically starts the battery maintenance function without the user even noticing, but energy is still saved while in hibernation since no active components are needed for the charging to start. Even if the charger is not connected to the mains, i.e. is powerless, it will still be recognized by the device placed in the charger and an indication can be given to the user to connect the charger to the mains power.

It is apparent to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.

Claims

A method for maintaining a battery, characterized in that the method comprises the steps of:

detecting a magnetic field between a battery powered device and a battery charger; establishing communication between a wireless battery charger and the battery powered device to determine whether the battery powered device is placed in the battery charger; and

if communication between the wireless the battery charger and the battery powered device fails, indicating this to the user.

The method for maintaining a battery according to claim 1 , further comprising a step of starting a battery maintenance function upon receipt to the communication.

The method for maintaining a battery according to claim 1 or 2, characterized in that if no magnetic field is detected no communication attempt is made.

The method for maintaining a battery according to claim 1 or 2, characterized in that if no communication can be established the battery maintenance function is not started.

The method for maintaining a battery according to claim 3 or 4, wherein the step of detecting will be repeated and after a delay or attempts will go to operation mode if no magnetic field has been detected or no communication has been established.

The method for maintaining a battery according to claim 1 , characterized in that the battery maintenance function comprises the steps of establishing whether the battery needs to be charged and starting a battery charging function if the battery needs to be charged or entering an operation mode.

The method of maintaining a battery according to claim 1 , characterized in that if the battery maintenance function cannot be started an indication is shown to the user.

A battery charger characterized in that it comprises:

a primary coil for inductive charging of a battery of a battery powered device;

a charger controller;

means for forming a magnetic field; and

means for communication with a battery powered device.

9. The battery charger according to claim 6, characterized in that it is configured for charging a device comprising a secondary coil, a controller, means for forming a magnetic field, means for communicating with the charger, a battery to be charged and a secondary converter.

10. The battery charger according to claim 8 or 9, wherein the means for forming the magnetic field is a magnet and/or a magnetic sensor.

1 1 . The battery charger according to claim 8 or 9, wherein the means for communication is a RF transceiver.

12. The battery charger according to claim 8 or 9, wherein the means for communication is an inductive loop.

13. The battery charger according to claim 7 or 8, wherein the means for forming the magnetic field is a permanent magnet and a magnetic relay.