Technical field

The present disclosure relates to an energy transfer device for an electric power tool or the like.

Background

Electric power tools are usually powered with battery packs that are inserted in a slot in the power tool. While one battery pack is used, another may be charged in a charger unit. Proposals have been made to instead include batteries in backpacks to allow for more stored energy.

A general problem associated with problem with power tools and their energy supply arrangements is how to provide efficient and flexible use of batteries and the like.

Summary

One object of the present disclosure is therefore to provide an energy transfer device that provides for improved efficiency and flexibility. This object is achieved by means of an energy transfer device as defined in claim 1. More specifically, in an energy transfer device for a power tool or the like, the transfer unit connects a storage side to a charge/discharge-, C/D-, -side. The storage side comprises connectors for at least two batteries, and the C/D-side comprises a charge/discharge-, C/D-, connector for a power tool or the like, wherein the transfer unit is configured both to simultaneously and sequentially connect the batteries to the C/D-connector. This allows the batteries to be charged and discharged in a number of different ways, and a charging- or discharging strategy may be optimized for instance depending on the status of the respective batteries. This allows the energy transfer device to adapt to any situation and provide a close to optimum performance.

The energy transfer device may comprise at least one converter and at least one connecting device, and be configured to either connect a battery to the C/D- connector directly via the connecting device or in an up- or down-converting manner via the converter. This allows the flexibility of either connecting the battery to a charger or a tool or similar with small or no switching losses via the connecting device or, if up- or down-conversion or balancing between different batteries is needed, via the converter.

It is also possible to provide two or more converters, which each are configured to connect a battery to the C/D-connector in an up- or down-converting manner.

A connecting device may be in the form of a static switch.

The converter may a Buck-Boost converter, such as a four-switch Buck-Boost converter. Such a converter provides the advantage of allowing both up- and down converting. Alternatively, the converters may be a converter in the group comprising: Buck-converters, Boost-converters and similar topology converters.

It is possible to provide a connecting device and a converter connected in parallel for each battery to individually choose the means for energy transfer for each battery.

Another option is to provide two or more connecting devices connected in parallel for each battery, each connecting device being configured to connect the battery to a different converter in a set of converters. This makes possible, the use of fewer converters for a given number of batteries as two or more batteries can use one converter sequentially. Alternatively, a connecting device may be provided for each battery, and the energy transfer device is configured to connect one battery in a set of batteries to a converter.

The device may be configured to alternate between different charging- and discharging modes.

In a first mode (A), the batteries are discharged sequentially, one battery at a time, or simultaneously, using converters to balance the connected batteries.

In a second mode (B) two or more batteries are charged sequentially, one battery at a time, or simultaneously, using converters to balance the connected batteries.

In a third mode (C) energy is transferred from one battery to another, allowing batteries e.g. to be equalized.

In a fourth mode (D), the batteries may be charged or discharged sequentially, one battery at a time and via a static switch. In a fifth mode (E), a first battery is charged or discharged via a static switch, while at least one other battery is charged or discharged via a converter, configured to adapt charging- or discharging voltage according to the voltage of said first battery. This allows one battery to be charged or discharged without switching losses while at the same time using two or more batteries simultaneously.

The batteries may be Lithium-Ion batteries.

The energy transfer device may be included in a backpack which allows use of several relatively heavy batteries in field use.

Such a backpack may include a USB charger output socket.

Brief description of the drawings

Fig 1 illustrates schematically an arrangement where a multi-battery unit is used.

Fig 2 illustrates a basic configuration for a multi-battery unit with an energy transfer device according to a first example.

Fig 3 shows basic components of the configuration in fig 2.

Fig 4 illustrates a basic configuration for a multi-battery unit with an energy transfer device according to a second example.

Fig 5 illustrates a basic configuration for a multi-battery unit with an energy transfer device according to a third example.

Fig 6 illustrates a basic configuration for a multi-battery unit with an energy transfer device according to a fourth example.

Fig 7 illustrates generally an example of a system overview for a multi-battery unit with an energy transfer device.

Detailed description

The present disclosure relates to battery driven systems, particularly but not exclusively intended for power tools. Battery driven power tools exist in various configurations depending on intended use and power requirements. In low-power, infrequently used tools, detachable single-use batteries may in principle be used and then discarded when depleted, e.g. AA batteries. As a next, step rechargeable batteries may be used. In more power-demanding applications, dedicated rechargeable battery packs are used which are optimized for the intended application and optionally may comprise a charging/de-charging interface that may communicate with e.g. the power tool and/or a charging device to control charging and de-charging of the battery pack. Although such a battery may be built into e.g. a power tool. It is much preferred to have a number of detachable battery packs, where one can be used with e.g. a power tool while another is being charged so that almost continuous use of the power tool is made possible.

By a battery pack is here generally meant a battery unit comprising one or more accumulator cells capable of delivering output power within a voltage range.

For high-power power tools there exist so-called backpack solutions, where a user carries a backpack comprising high power batteries, where the backpack is connected to a power tool via a cable.

The present disclosure relates to an energy transfer device that is configured to connect a plurality of battery units to a power tool, or, during charging, to a charging device. The energy transfer device provides a level of flexibility that allows the battery units to be used in a number of ways depending on the intended application and the status of individual battery units among the plurality of battery units.

Typically, the battery units may be Lithium-Ion batteries.

Fig 1 illustrates schematically an arrangement 1 where a multi-battery unit or energy transfer device 3 is used. In the arrangement 1 according to this example, the energy transfer device 3 is a backpack unit which is connected to a power tool in the form of a chainsaw 5 for powering the latter. The energy transfer device comprises slots for three battery units 7, which in the example are identical although this is not necessary. The energy transfer device 3 comprises a cable 9 for supplying electric energy to the power tool 5.

The battery units 7 may be of a type that could be fitted directly with the power tool 5, if desired, although the present example allows the power tool to be operated for much longer and to use battery units in a much more flexible manner, as will be discussed. Further, as a power tool 5 with no such battery unit 7 directly fitted thereto is much lighter, the user ergonomic is improved. Carrying battery units 7 in a backpack is less demanding. However, it would also be possible e.g. to integrate the energy transfer device for instance in the power tool or another unit.

Needless to say, there may be only two or more than three slots for battery units 7 in the backpack. Additionally, there may also be provided one or more additional internal battery units (not shown) which may be fixedly connected to the backpack and may or may not be otherwise identical to the detachable battery units 7.

Fig 2 illustrates one example of a basic configuration for a multi-battery unit with an energy transfer device 3. Generally, the energy transfer device 3 connects a storage side 2 to a charge/discharge-, C/D-, -side 4. On the storage side 2, connectors 6 are provided for the batteries 7. The C/D-side 4 is used for connecting to a power tool or the like, but may also be connected to some kind of charging unit, although this is not necessary. It would also be possible to charge the batteries 7 separately, in dedicated charging devices as is well known per se. The C/D-side 4 could therefore in some embodiments be designated as a discharge-, D-, side. In any case, the C/D- side 4 comprises a charge/discharge-, C/D-, connector 15 for connecting with a power tool or the like, but optionally thus also to a charger or the like.

The energy transfer unit 3 of fig 2 is used with three separate batteries 7, which each has a connector 6. As mentioned, slots and connectors 6 for more or fewer batteries 7 may be provided, and it is not necessary that all available connectors 6 are used. In fig 2 thus, one or two batteries could be removed, and the energy transfer unit could still be used, with reduced power and/or operating time.

In the example schematically illustrated in fig 2, one converter 11 and one solid state switch 13 is provided for each connected battery 7, and the converter and switch in parallel connect each battery connector 6 with the C/D-connector 15.

This is described in greater detail in fig 3.

The converter 11 may as illustrated be a four switch Buck/Boost converter, although other converter topologies may be conceivable such as Boost-, Buck-, or similar topology converters depending on desired properties. A Buck/Boost converter, however, is a preferred choice as it offers great flexibility. In the illustrated case, the converter is a four-switch converter capable of transferring energy both from the storage side 2 to the C/D-side 4, and in the opposite direction. Thus, both charging and discharging is made possible. Further, a Buck/Boost converter is capable of both up-converting and down-converting, which provides additional flexibility. For instance, a high voltage tool can be powered by lower voltage batteries, and it becomes possible to charge batteries with general purpose low voltage chargers or using power sources with unregulated output voltage such as solar panels or energy storage devices such as battery modules, etc. Other converters with lower complexity can be used if a more limited flexibility is acceptable.

The solid-state switch or relay 13 can be used as an alternative to the converter 11 to connect or disconnect the battery to/from the C/D-connector 15 without the converter’s switching losses. With the lower losses, the solid-state switch or relay 13 gives an advantage of allowing high power transfer at low cost. In principle a legacy mechanical relay could be used, although solid stated switches are preferred.

A filter 12 or a capacitor Co , etc., with an inrush limiting function may be provided at each battery connection. Similarly, a capacitor may be provided at the C/D-connector side.

At least five different operating modes can be considered for an energy transfer device 3 of this kind.

To start with, in a first operating mode here called mode A, energy transfer takes place from the storage side 3 to the discharge side 4, i.e. typically Li-Ion batteries 7 are discharged while powering a power tool on the discharge side. In this operating mode, the batteries on the storage side can be used one by one in a sequential manner. Converters are used to output the desired voltage.

Alternatively, two or more batteries 7 may be used in combination. In this latter case, the voltage on the two or more batteries 7 can be an arbitrary voltage in a permissible voltage range. The power used from each battery can be arbitrary as well, depending on the required power on the output, the capabilities of the connected batteries and/or a set-point defined based on information gathered from the connected inputs and outputs. Further, in this operating mode, the energy transfer direction can for short periods of time be reversed when e.g. an outdoor power tool is used in regenerative braking mode. In a second mode, here called mode B, energy transfer takes place from the C/D- to the storage side, typically for charging of the batteries. In this operating mode, the batteries on the storage side 2 can be charged one by one in a sequential manner or with two or more inputs used together. In the latter case, the voltage and current on each input on the storage side is defined per the charging characteristics requirements needed for the respective connected batteries being charged. The power drawn from the C/D-side output is defined mainly by the capabilities of the connected device such as a charger or a power supply on the C/D--side and the requirements and capabilities of the batteries.

In a third mode here called mode C, energy is transferred from a first to a second battery 7 on the storage side. This can be done to balance the available energy between the two batteries, i.e. make sure that each battery is used, i.e. charged or discharged, at a suitable level in terms of power and/or voltage. This mode in principle can be combined with modes A and B above as well as mode E, below, depending on the topology used.

In a fourth mode here called mode D, energy is transferred from the storage side 2 to the C/D-side as in the first mode, or vice-versa, but using the solid state switches 13 as the means for energy transfer. This limits the output depending on the status of the battery used, but switching losses are limited.

In a fifth mode, here called mode E, energy is transferred from a first battery 7 at the storage side 2 to the C/D-side as in the fourth mode, using the solid state switch 13 as the means for energy transfer. However, from one or more other battery 7, energy is simultaneously transferred using the converter. Then, the voltage output from the first battery 7 is designated as a master voltage, and the voltage from the one or more other batteries 7 is adapted to this master voltage by up-converting or down converting.

Different layouts are possible and some, but not all, are capable of operating in all the above-mentioned modes. Generally, converters are needed for feeding power from two or more batteries in parallel while sequential use of batteries only requires static switches. A boost-buck converter allows output voltages higher than the input voltages while buck converter only allows lower output voltages, etc. It is considered desirable to allow a wide range of battery voltages, e.g. 20 - 44V, and at the same time allow a wide range of output (or charging) voltages, e.g. 9 - 44V. As illustrated, the energy transfer device may be capable of communicating both with inserted battery units and with the power tool or the like. This makes it possible to adapt power transmission in an optimal way depending on used batteries and the power tool or the like operated.

Fig 4 illustrates a basic configuration for a multi-battery unit with an energy transfer device 3 according to a second example. In this example, the solid-state switches 13 of fig 2 are dispensed with, and the energy transfer takes place exclusively via the converters 11. This configuration has a reduced complexity, but at the cost of the option of avoiding switching losses which is possible with the static switches.

Fig 5 illustrates a basic configuration for a multi-battery unit with an energy transfer device 3 according to a third example. In this case, four batteries 7 are connected to the device via battery connectors 6. For each battery there is provided two static switches 13, where one switch connects the battery 7 to a first converter 11 , and the second to another. This provides an almost full flexibility with only two converters for four batteries.

Fig 6 illustrates a basic configuration for a multi-battery unit with an energy transfer device according to a fourth example. This is a reduced version of the example in fig 5 where only one static switch 13 is provided per battery 7. This provides the option of selecting which out of two batteries are connected to one converter 11.

Fig 7 illustrates generally an example of a system overview for a multi-battery 7 unit with an energy transfer device, e.g. formed as a backpack 3. The system may be controlled by one or more microcontroller units, MCUs 21. The MCU 21 may communicate with the batteries via e.g. a serial interface or short-range radio interface RXTX to periodically or continuously receive data regarding charging status, preferred voltage, temperature etc.

The MCU 21 may further communicate with tool 5 or the like to which the backpack is connected. In the case of a tool 5 or other power consumer, the MCU 21 may retrieve data regarding required power and voltage to connect batteries and/or control converters accordingly. Alternatively, the MCU 21 can communicate the available power capacity to the tool 5 that adapts accordingly. It should be noted that a power tool 5 intermittently can generate power by regenerative braking and such actions should be reported to the MCU 21 to adapt the energy transfer device accordingly. This communication interface can be wireless using e.g. a suitable short-range communication interface RXTX or can take place via a cable 9 connecting the backpack to a tool, e.g. using a serial communication protocol.

When instead connected to a charger or general power supply, the MCU 21 can request a desired power and voltage level from the charger using the same communication interface, or be informed regarding the charging capacity available. However, with a converter layout as illustrated in fig 3 for instance, MCU of the power transfer unit can measure the input voltage and control the converters to supply suitable charging power to each battery.

The system may further include cooling fans 22, typically for the power electronics and one for each battery 7. The power conversion unit may provide outputs 23 for such fans 22. Additionally, for instance a USB charger outlet 25 may be provided on the backpack 3.

The MCU 21 may further be connected to a user interface 27 allowing a user to control functions of the backpack 3, typically at least an ON/OFF switch. However, it would be possible to make the backpack 3 autonomous in this sense, as controlling the tool 5 communicating with the backpack 3 would be sufficient. Finally, the MCU 21 may provide communication with central management means 29 such as a fleet managements system monitoring status of several devices, typically when used professionally, e.g. to keep track of battery status and to plan replacements, etc.

The present disclosure is not limited to the above-described examples, and may be varied and altered in different ways within the scope of the appended claims.