Dual-motor stick cleaner

Abstract

The present disclosure relates to a vacuum cleaner (10) and a method of controlling operation of the vacuum cleaner (10).In an aspect, the vacuum cleaner (10) comprises a main body (11) comprising a first suction inlet (17), a first motor fan unit (18) and a first battery (19) configured to power the first motor fan unit (18), the first motor fan unit (18) being configured to create a first airflow (32) via the first suction inlet (17) through a common airflow path (20). The vacuum cleaner (10) further comprises a portable vacuum cleaner unit (16) arranged to be detachable from the main body (11) and comprising a second suction inlet (21), a dust separation unit (22), a second motor fan unit (23) and a second battery (24) configured to power the second motor fan unit (23), the second motor fan unit (23) being configured to create a second airflow (33) via the second suction inlet (21) to the dust separation unit (22), wherein the second suction inlet (21) is configured to connect, upon being attached to the main body (11), to the common airflow path (20) via a first opening (25) of the main body (11), the portable vacuum cleaner unit (16) further comprising an air outlet (26) configured to connect to a second opening (27) in the main body (11) to connect the common airflow path (20) via the dust separation unit (22) to the first motor fan unit (18) to cooperatively have the first airflow (32) and the second airflow (33) create a common airflow (34) through the common airflow path (20) during operation of the vacuum cleaner (10).

Description

DUAL-MOTOR STICK CLEANERTECHNICAL FIELD

[0001] The present disclosure relates to a vacuum cleaner and a method of controlling operation of the vacuum cleaner.BACKGROUND

[0002] Different types of vacuum cleaners are known, such as canister vacuum cleaners, robotic vacuum cleaners, central vacuum cleaners and stick-type vacuum cleaners. Stick vacuum cleaner generally has an elongated body with a nozzle in one end for collecting dust and debris and a handle in the other end.

[0003] In some stick type vacuum cleaners, a portable vacuum cleaner unit is detachable from the elongated body and may be used independently as a handheld vacuum cleaner separate from the elongated body. This maybe practical e.g. for sucking up crumbs from tables and similar. This also allow a user to reach surfaces where a nozzle of the body would not fit.

[0004] The portable vacuum cleaner unit commonly comprises a fan and motor for creating an airflow collecting and transporting the dust to a separation chamber. The fan and motor of the portable vacuum cleaner will be operated to create an airflow both when the portable vacuum cleaner unit is attached to the elongated body, in which case the airflow occurs via the nozzle of the elongated body, and in solo mode when the portable vacuum cleaner unit is detached from the elongated body for solo operation.

[0005] A problem with this construction is that a powerful and thus bulky and space consuming motor is required for operating the fan to create the airflow both when the portable vacuum cleaner unit is operated in attached mode and detached mode.SUMMARY

[0006] One objective is to solve, or at least mitigate, this problem in the art and thus to provide an improved vacuum cleaner.

[0007] This objective is attained in a first aspect by a vacuum cleaner comprising a main body comprising a first suction inlet, a first motor fan unit and a first batteryconfigured to power the first motor fan unit, the first motor fan unit being configured to create a first airflow via the first suction inlet through a common airflow path. The vacuum cleaner further comprises a portable vacuum cleaner unit arranged to be detachable from the main body and comprising a second suction inlet, a dust separation unit, a second motor fan unit and a second battery configured to power the second motor fan unit, the second motor fan unit being configured to create a second airflow via the second suction inlet to the dust separation unit, wherein the second suction inlet is configured to connect, upon being attached to the main body, to the common airflow path via a first opening of the main body, the portable vacuum cleaner unit further comprising an air outlet configured to connect to a second opening in the main body to connect the common airflow path via the dust separation unit to the first motor fan unit to cooperatively have the first airflow and the second airflow create a common airflow through the common airflow path during operation of the vacuum cleaner.

[0008] This objective is attained in a second aspect by a method of controlling operation of a vacuum cleaner. The vacuum cleaner comprises a main body comprising a first suction inlet, a first motor fan unit and a first battery configured to power the first motor fan unit, the first motor fan unit being configured to create a first airflow via the first suction inlet through a common airflow path. The vacuum cleaner further comprises a portable vacuum cleaner unit arranged to be detachable from the main body and comprising a second suction inlet, a dust separation unit, a second motor fan unit and a second battery configured to power the second motor fan unit, the second motor fan unit being configured to create a second airflow via the second suction inlet to the dust separation unit, wherein the second suction inlet is configured to connect, upon being attached to the main body, to the common airflow path via a first opening of the main body, the portable vacuum cleaner unit further comprising an air outlet configured to connect to a second opening in the main body to connect the common airflow path via the dust separation unit to the first motor fan unit to cooperatively have the first airflow and the second airflow create a common airflow through the common airflow path during operation of the vacuum cleaner. The vacuum cleaner further comprises a controller being configured to estimate remaining runtime of each of the first battery and the second battery, determine whether or not estimated remaining runtime of the second battery is shorter thanthat of the first battery, and if so to decrease output power of the second motor fan unit.

[0009] Advantageously, in the first aspect, the first motor fan unit and the second motor fan unit cooperatively creates the common airflow through the common airflow path and the dust separation unit during operation of the vacuum cleaner.

[0010] Further advantageous, in the second aspect, the controller will decrease output power of the second motor fan unit upon detecting that remaining runtime of the second battery is longer than that of the first battery, until the remaining runtime of the first battery and the second battery is the same (or at least similar), thereby avoiding a scenario where the second battery discharges long before the first battery is about to discharge due to the portable vacuum cleaner unit being operated in extended solo operation.

[0011] In an embodiment, the air outlet of the portable vacuum cleaner unit is arranged with a closing member configured to close the air outlet upon the portable vacuum cleaner unit being detached from the main body.

[0012] In an embodiment, the main body further comprises a first exhaust air outlet via which the first airflow travelling in a first airflow path connecting to the common airflow path is exhausted.

[0013] In an embodiment, the portable vacuum cleaner unit further comprises a second exhaust air outlet via which the second airflow travelling in a second airflow path connecting to the common airflow path is exhausted.

[0014] In an embodiment, if the estimated remaining runtime of the second battery is equal to that of the first battery, output power of the second motor fan unit is controlled in accordance with the selected cleaning programme.

[0015] In an embodiment, if the output power of the second motor fan unit is to be decreased, a difference between the remaining runtime for the first battery and the remaining runtime for the second battery should exceed a selected control threshold.

[0016] In an embodiment, the first motor fan unit comprises a first fan and a first motor arranged to operate the first fan and the second motor fan unit comprises a second fan and a second motor arranged to operate the second fan.

[0017] In an embodiment, the vacuum cleaner further comprises a control arrangement configured to be operable by a user to control operation of the first and second motor fan unit to adjust the common airflow through the common airflow path.

[0018] In an embodiment, the remaining runtime of the first and second battery is estimated by determining current power level of the respective battery or a total operating time of the respective battery.

[0019] In an embodiment, the controller is arranged in the portable vacuum cleaner unit.

[0020] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which:

[0022] Figure 1 shows a stick vacuum cleaner 10 perspective view according to an embodiment;

[0023] Figure 2 illustrates a sectional view of the vacuum cleaner of Figure 1;

[0024] Figure 3 illustrates an embodiment of a portable vacuum cleaner unit having been detached from a main body of the vacuum cleaner;

[0025] Figure 4 shows a flowchart illustrating a method of controlling operation of the vacuum cleaner according to an embodiment; and

[0026] Figure 5 illustrates the vacuum cleaner in an embodiment.DETAILED DESCRIPTION

[0027] The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown.

[0028] These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description.

[0029] Figure 1 illustrates a vacuum cleaner 10 in perspective view according to an embodiment. This particular type of vacuum cleaner is known as an upright cleaner or stick cleaner. The vacuum cleaner 10 is powered by two chargeable batteries as will be described.

[0030] The vacuum cleaner 10 comprises a main body 11 housing various parts of the vacuum cleaner 10 as will be described.

[0031] The vacuum cleaner 10 collects dust and debris from a floor, furniture, carpets, etc. via a suction inlet of a nozzle 12 at a distal end of the main body 11.

[0032] A first handle 13 is typically arranged at a distal end of the main body 11 to be held by a user for moving the vacuum cleaner 10 over a surface to be cleaned. The first handle 13 may optionally comprise a first control arrangement 15a, e.g. a push button or a slider, for control of at least one of a fan effect, a nozzle function or any other vacuum cleaner function which may need to be adjustable. Hence, the first control arrangement 15a can be operated by a user to turn the vacuum cleaner 10 on / off.

[0033] Further attached to the main body 11 is a portable vacuum cleaner unit 16 which is detachable from the main body 11 and maybe used independently as a handheld vacuum cleaner separate from the stick vacuum cleaner 10. This is practical e.g. for cleaning up crumbs and dust from tables and similar.

[0034] The portable vacuum cleaner unit 16 comprises a second handle 14 typically being arranged at a distal end of the portable vacuum cleaner unit 16 to be held by a user for moving the portable vacuum cleaner unit 16 over a surface to be cleaned. The second handle 14 may optionally comprise a second controlarrangement 15b, e.g. a push button or a slider, for control of at least one of a fan effect, a nozzle function or any other function for controlling the portable vacuum cleaner unit 16 which may need to be adjustable. Hence, the second control arrangement 15b can be operated by a user to turn the portable vacuum cleaner unit 16 on / off.

[0035] Figure 2 illustrates a sectional view of the vacuum cleaner 10 (excluding the first handle 13).

[0036] As mentioned, the main body 11 comprises a first suction inlet 17 arranged in the nozzle 12. Further, the main body 11 comprises a first motor fan unit 18 and a first battery 19 configured to power the first motor fan unit 18. As shown in Figure 2, the first motor fan unit 18 is configured to create a first airflow 32 via the first suction inlet 17 through a common airflow path 20.

[0037] As is understood, the first motor fan unit 18 comprises a first motor 18a configured to rotate a first fan 18b for creating the first airflow 32.

[0038] The vacuum cleaner 10 further comprises the portable vacuum cleaner unit 16 arranged to be detachable from the main body 11 and comprising a second suction inlet 21 and a dust separation unit 22 where the debris and dust entering the first suction inlet 17 is transported via the common airflow path 20 and the second suction inlet 21.

[0039] The dust separation unit 22 is hence configured to separate dust and debris from air flowing through the dust separation unit 22. To this end, the dust separation unit 22 may comprise a cyclone separator or other means for separating the dust, such as a filter, a dust bag or the like.

[0040] The portable vacuum cleaner unit 16 further comprises a second motor fan unit 23 and a second battery 24 configured to power the second motor fan unit 23, which second motor fan unit 23 is configured to create a second airflow 33 via the second suction inlet 21 to the dust separation unit 22. The second motor fan unit 23 comprises a second motor 23a configured to rotate a second fan 23b for creating the airflow.

[0041] As illustrated in Figure 2, the second suction inlet 21 is configured to connect - upon being attached to the main body 11 - to the common airflow path 20 via a first opening 25 of the main body 11.

[0042] The portable vacuum cleaner unit 16 further comprises an air outlet 26 configured to connect to a second opening 27 in the main body 11 to connect the common airflow path 20 via the dust separation unit 22 to the first motor fan unit 18 to cooperatively have the first airflow 32 and the second airflow 33 create a common airflow 34 through the common airflow path 20 during operation of the vacuum cleaner 10.

[0043] Advantageously, with this embodiment, the first motor fan unit 18 and the second motor fan unit 23 cooperatively creates the common airflow 34 through the common airflow path 20 and the dust separation unit 22 during operation of the vacuum cleaner 10.

[0044] With further reference to Figure 3, in an embodiment the main body 11 of the vacuum cleaner 10 comprises a first exhaust air outlet 35 via which the first airflow 32 is exhausted, the first airflow 32 travelling in a first airflow path 36 connecting to the common airflow path 20 via the second opening 27 to cooperatively with the second airflow 33 create the common airflow 34.

[0045] Similarly in an embodiment, the portable vacuum cleaner unit 16 comprises a second exhaust air outlet 37 via which the second airflow 33 is exhausted, the second airflow 33 travelling in a second airflow path 38 connecting to the common airflow path 20 to cooperatively with the first airflow 32 create the common airflow 34.

[0046] Further, the separation unit may comprise a filter or the like (not shown) at a location downstream of the position where the common airflow path 20 branches into the first airflow path 36 and the second airflow path 38. In addition, or alternatively, separate filters may be arranged downstream of each motor 18a, 23a.

[0047] Figure 3 illustrates an embodiment of the portable vacuum cleaner unit 16 having been detached from the main body 11 of the vacuum cleaner 10 to be operated separately for removing dust from an object via the second suction inlet 21.

[0048] As shown in Figure 3, the air outlet 26 of the portable vacuum cleaner unit 16 is arranged with a closing member 28 for covering the air outlet 26 upon the portable vacuum cleaner unit 16 being operated separately to avoid any air undesirably flowing through the air outlet 26. The closing member 28 may e.g. be spring -biased such that the applied spring -force closes the closing member 28 uponthe portable vacuum cleaner unit 16 being detached, while a protruding member or the like on the main body n pushes the closing member 28 open radially in a direction towards an interior of the portable vacuum cleaner unit 16 upon the cleaner unit 16 being attached to the main body 11 to allow the first airflow path 36 to connect to the common airflow path 20.

[0049] Now, since a user occasionally may detach the portable vacuum cleaner unit 20 from the main body 11 for solo operation, the second battery 24 will discharge before the first battery 18 since the first battery 18 only is operated when the portable vacuum cleaner unit 16 is attached to the main body 11 for operation of the vacuum cleaner 10.

[0050] As is understood, if the second battery 24 fully discharges, operation of the vacuum cleaner 10 will be less efficient utilizing only the first motor fan unit 18 and the first battery 19. Further, even if the first motor fan unit 18 would be capable of producing a strong enough airflow through the airflow path 20 and the dust separation unit 22 during operation of the vacuum cleaner 10, a check valve or the like would have to be arranged upstream of the dust separation unit 22 as air may enter the portable vacuum cleaner unit 16 from an end of the portable vacuum cleaner unit 16 where the airflow normally would exit during operation of the second motor fan unit 23. An alternative to utilizing a check valve is to alert the user that the second battery 24 has discharged (for instance using an audial alert or visual alert provided by a light emitting diode or the like) such that the user can turn of the vacuum cleaner 10, or to implement functionality that turns the vacuum cleaner 10 off once the second battery 24 discharges.

[0051] In an embodiment, the vacuum cleaner 10 further comprises a controller 29 being configured to estimate remaining runtime of each of the first battery 18 and the second battery 24 and if the estimated remaining runtime of the second battery 24 is shorter than that of the first battery 18, maximum allowable output power of the second motor fan unit 23 is decreased in order to adapt the remaining runtime of the second battery 24 to that of the first battery 18.

[0052] The controller 29 may be arranged in the main body 11 or in the portable vacuum cleaner unit 16. Alternatively, both the main body 11 and the portable vacuum cleaner unit 16 comprises a controller configured to estimate remainingruntime. As is understood, the vacuum cleaner 10 is typically already equipped with one or more controllers which may be utilized for the purpose.

[0053] In this exemplifying embodiment, it is assumed that the controller 29 is arranged in the portable vacuum cleaner unit 16 and being configured to be in communicative communication with both the first battery 19 and the second battery 24 to estimate the remining runtime, for instance by determining a current power level of the respective battery 19, 24 or a total operating time of the respective battery 19, 24.

[0054] An advantage of arranging the controller 29 in the portable vacuum cleaner unit 16 is that measurements maybe performed on the second battery 24 even with the portable vacuum cleaner unit 16 detached from the main body 11.

[0055] Figure 4 shows a flowchart illustrating a method of controlling operation of the vacuum cleaner 10 according to an embodiment.

[0056] Assuming for instance that the vacuum cleaner 10 has been fully charged such that the remaining runtime of the first battery 18 and the second battery 24 is the same upon running a given cleaning programme as selected by the user with the control arrangement 15.

[0057] In a first step S101, when the vacuum cleaner 10 is operated according to the selected cleaning programme, the controller 29 estimates the remaining runtime Ri, R2 of the first battery 19 and the second battery 24, respectively, and determines in step S102 whether or not the remaining runtime R2 of the second battery 24 is shorter than the remaining runtime Ri of the first battery 19.

[0058] Since at this stage this is yet not the case, the controller 29 will continue to control the first motor fan unit 18 and the second motor fan unit 23 according to the selected cleaning programme.

[0059] Assuming further that the user cleans the floor by running the vacuum cleaner 10 in the selected cleaning programme for about 5 minutes before detaching the portable vacuum cleaner unit 20 from the main body 11 to clean crumbs off of the kitchen table for a couple of minutes.

[0060] Upon the user attaching the portable vacuum cleaner unit 16 to the main body 11 of the vacuum cleaner 10, the controller 29 will in step S101 perform anestimation of the remaining runtime Ri, R2 of both the first battery 19 and the second battery 24.

[0061] In this particular example, the portable vacuum cleaner unit 16 and thus the second battery 24 will at this stage have been operated for a total of 7 minutes after having been fully charged, while the first battery 19 has been operated for 5 minutes.

[0062] The controller 29 may measure total operating time of the respective battery 19, 24, remaining power level, or any other appropriate metric for estimating remaining runtime in step S101.

[0063] In step S102, the controller 29 concludes that the remaining runtime R2 of the second battery 24 now is shorter than the remaining runtime Ri of the first battery 19. If in this example it is assumed that the runtime for each battery is 60 minutes with the selected cleaning programme, the remaining runtime Ri of the first battery is 60 - 5 = 55 minutes while the remaining runtime R2 of the second battery 24 is 60 - 7 = 53 minutes.

[0064] If the first fan 18b is operated at A rotations per minute (rpm) while the second fan 23b is operated at B rpm with the selected cleaning programme, the controller 29 will now operate the second fan 23b at B’ rpm, where B > B’. This is typically performed by lowering the output power of the second motor 23b.

[0065] Hence, in step S104, the decrease in output power of the second motor fan unit 23 is maintained until the controller 29 again determines in step S102 that the remaining runtime R2 of the second battery 24 is equal to the remaining runtime Ri of the first battery 19.

[0066] The controller 29 will as a result (as shown in step S103) control the first motor fan unit 18 and the second motor fan unit 23 according to the selected cleaning programme, i.e. the second fan 23b is again operated at B rpm.

[0067] Advantageously, this avoids a scenario where the second battery 24 discharges before the first battery 19 due to solo operation of the portable vacuum cleaner unit 16, in which case the vacuum cleaner needs to be recharged.

[0068] In an embodiment, to avoid a scenario where the output power of the second motor fan unit 23 is repeatedly adjusted as a result of the remaining runtime R2 of the second battery 24 being estimated to fall below the remining runtime Ri ofthe first battery 19, which may occur to the natural tolerance variations in components of the vacuum cleaner 10 rather than being due to legitimate differences in remaining runtime.

[0069] In such embodiment, rather than determining in step S102 whether R2 < Ri, it may alternatively be determined whether R2 + A < Ri, where A is control threshold selected such that the output power of the second motor fan unit 23 is adjusted if R2 indeed is shorter than Ri. In other words, a difference between the remaining runtime Ri for the first battery 19 and the remaining runtime R2 for the second battery 24 must exceed the selected control threshold A, i.e. Ri - R2 > A.

[0070] Figure 5 schematically illustrates the vacuum cleaner 10 according to an embodiment, where the steps of the method of controlling operation of the vacuum cleaner 10 in practice are performed by the controller 29 embodied in the form of one or more microprocessors arranged to execute a computer program 30 downloaded to a storage medium 31 associated with the microprocessor, such as a Random Access Memory (RAM), a Flash memory or a hard disk drive. The processing unit 29 is arranged to cause the vacuum cleaner 10 to carry out the method according to embodiments when the appropriate computer program 30 comprising computerexecutable instructions is downloaded to the storage medium 31 and executed by the processing unit 29, i.e. to estimate remaining runtime of each of the first battery 19 and the second battery 24, to determine whether or not estimated remaining runtime of the second battery 24 is shorter than that of the first battery 19, and if so to decrease output power of the second motor fan unit 23.

[0071] The storage medium 31 may also be a computer program product comprising the computer program 30. Alternatively, the computer program 30 may be transferred to the storage medium 31 by means of a suitable computer program product, such as a Digital Versatile Disc (DVD) or a memory stick. As a further alternative, the computer program 30 maybe downloaded to the storage medium 31 over a network. The processing unit 29 may alternatively be embodied in the form of a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD), etc.

[0072] The aspects of the present disclosure have mainly been described above with reference to a few embodiments and examples thereof. However, as is readilyappreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

[0073] Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.List of references:10 - Vacuum cleaner 35 - Second exhaust air outlet n - Main body 36 - First airflow path12 - Nozzle 37 - Second exhaust air outlet13 - First handle 38 - Second airflow path14 - Second handle15a - First control arrangement15b - Second control arrangement16 - Portable vacuum cleaner unit17 - First suction inlet18 - First motor fan unit18a - First motor18b - First fan19 - First battery20 - Common airflow path21 - Second suction inlet22 - Dust separation unit23 - Second motor fan unit23a - Second motor23b - Second fan24 - Second battery25 - First opening26 - Air outlet27 - Second opening28 - Closing member29 - Controller30 - Computer program31 - Storage medium32 - First airflow33 - Second airflow34 - Common airflow

Claims

CLAIMS1. A vacuum cleaner (10), comprising: a main body (n) comprising a first suction inlet (17), a first motor fan unit (18) and a first battery (19) configured to power the first motor fan unit (18), the first motor fan unit (18) being configured to create a first airflow (32) via the first suction inlet (17) through a common airflow path (20); and a portable vacuum cleaner unit (16) arranged to be detachable from the main body (11) and comprising a second suction inlet (21), a dust separation unit (22), a second motor fan unit (23) and a second battery (24) configured to power the second motor fan unit (23), the second motor fan unit (23) being configured to create a second airflow (33) via the second suction inlet (21) to the dust separation unit (22); wherein the second suction inlet (21) is configured to connect, upon being attached to the main body (11), to the common airflow path (20) via a first opening (25) of the main body (11), the portable vacuum cleaner unit (16) further comprising an air outlet (26) configured to connect to a second opening (27) in the main body (11) to connect the common airflow path (20) via the dust separation unit (22) to the first motor fan unit (18) to cooperatively have the first airflow (32) and the second airflow (33) create a common airflow (34) through the common airflow path (20) during operation of the vacuum cleaner (10).

2. The vacuum cleaner (10) of claim 1, the air outlet (26) of the portable vacuum cleaner unit (16) being arranged with a closing member (28) configured to close the air outlet (26) upon the portable vacuum cleaner unit (16) being detached from the main body (11).

3. The vacuum cleaner (10) of claims 1 or 2, the main body (11) further comprising: a first exhaust air outlet (35) via which the first airflow (32) travelling in a first airflow path (36) connecting to the common airflow path (20) is exhausted.

4. The vacuum cleaner (10) of any one of the preceding claims, the portable vacuum cleaner unit comprising: a second exhaust air outlet (37) via which the second airflow (33) travelling in a second airflow path (38) connecting to the common airflow path (20) is exhausted.

5. The vacuum cleaner (10) of any one of the preceding claims, further comprising: a controller (29) being configured to estimate remaining runtime of each of the first battery (19) and the second battery (24) and further to control output power of the second motor fan unit (23) for a selected cleaning programme, and if the estimated remaining runtime of the second battery (24) is determined to be shorter than that of the first battery (19), output power of the second motor fan unit (23) is decreased.

6. The vacuum cleaner (10) of claim 5, wherein if the estimated remaining runtime of the second battery (24) is equal to that of the first battery (19), output power of the second motor fan unit (23) is controlled in accordance with the selected cleaning programme.

7. The vacuum cleaner (10) of claims 5 or 6, wherein if the output power of the second motor fan unit (23) is to be decreased, a difference between the remaining runtime for the first battery (19) and the remaining runtime for the second battery (24) should exceed a selected control threshold.

8. The vacuum cleaner (10) of any one of the preceding claims, the first motor fan unit (18) comprising a first fan (18b) and a first motor (18a) arranged to operate the first fan (18b) and the second motor fan unit (23) comprising a second fan (23b) and a second motor (23a) arranged to operate the second fan (23b).

9. The vacuum cleaner (10) of any one of the preceding claims, further comprising: a control arrangement (15a) configured to be operable by a user to control operation of the first and second motor fan unit (18, 23) to adjust the common airflow (34) through the common airflow path (20).

10. The vacuum cleaner (10) of any one of the preceding claims, the remaining runtime of the first and second battery (19, 24) being estimated by determining current power level of the respective battery (19, 24) or a total operating time of the respective battery (19, 24).

11. The vacuum cleaner (10) of any one of the preceding claims, the controller (29) being arranged in the portable vacuum cleaner unit (16).

12. A method of controlling operation of a vacuum cleaner (10), the vacuum cleaner (10) comprising: a main body (n) comprising a first suction inlet (17), a first motor fan unit (18) and a first battery (19) configured to power the first motor fan unit (18), the first motor fan unit (18) being configured to create a first airflow (32) via the first suction inlet (17) through a common airflow path (20); and a portable vacuum cleaner unit (16) arranged to be detachable from the main body (11) and comprising a second suction inlet (21), a dust separation unit (22), a second motor fan unit (23) and a second battery (24) configured to power the second motor fan unit (23), the second motor fan unit (23) being configured to create a second airflow (33) via the second suction inlet (21) to the dust separation unit (22); wherein the second suction inlet (21) is configured to connect, upon being attached to the main body (11), to the common airflow path (20) via a first opening (25) of the main body (11), the portable vacuum cleaner unit (16) further comprising an air outlet (26) configured to connect to a second opening (27) in the main body (11) to connect the common airflow path (20) via the dust separation unit (22) to the first motor fan unit (18) to cooperatively have the first airflow (32) and the second airflow (33) create a common airflow (34) through the common airflow path (20) during operation of the vacuum cleaner (10), the vacuum cleaner (10) further comprising a controller (29) being configured to: estimating (S101) remaining runtime of each of the first battery (19) and the second battery (24); determining (S102) whether or not estimated remaining runtime of the second battery (24) is shorter than that of the first battery (19); and if so: decreasing (S104) output power of the second motor fan unit (23).

13. The method of claim 12, the controller (29) being configured to, if the estimated remaining runtime of the second battery (24) is determined (S102) to be equal to that of the first battery (19): controlling (S103) the output power of the second motor fan unit (23) in accordance with the selected cleaning programme.

14. The method of claims 12 or 13, wherein if the output power of the second motor fan unit (23) is to be decreased, a difference between the remaining runtimefor the first battery (19) and the remaining runtime for the second battery (24) should exceed a selected control threshold if the output power.

15. A computer program (30) comprising computer-executable instructions for causing a vacuum cleaner (10) to perform steps recited in any one of claims 12-14 when the computer-executable instructions are executed on a controller (29) included in the vacuum cleaner(io).

16. A computer program product comprising a computer readable medium (31), the computer readable medium having the computer program (30) according to claim 15 embodied thereon.

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