Battery transfer carriages

Abstract

A battery transfer carriage 30, transfers a battery unit 22 to, and from, a vehicle 10 (e.g., forklift truck, tracked vehicle, tug, tractor, mobile elevated work platform, excavator, skid-steer vehicle, dumper). The battery transfer carriage comprises: a body (32-Fig.6) having a front and rear end (34,36-Fig.6); a battery platform for receiving and supporting a battery unit placed thereon; and a coupling component (e.g., projections (44-Fig.6)), disposed adjacent the front end of the carriage body. The battery platform extends to the front end of the carriage body, permitting a battery unit to be transferred between the battery platform and a battery-receiving surface of a vehicle in a translational motion across the front end of the carriage body. The coupling component engages with a complementary component of a vehicle body to couple the carriage body to the vehicle body, and to bear the weight of the front end of the carriage body. When the coupling component is engaged, in use, the front end of the carriage body is supported by the coupling component, and the height of the front end of the carriage body is determined by the height of the complementary component of the vehicle body. The battery unit can be moved in a sliding motion, or rolled on rollers (38-Fig.6), between the battery platform and the vehicle battery compartment.

Description

Technical Field This invention relates to battery transfer carriages for use in transferring a battery unit to and from a vehicle, to vehicles for use with such battery transfer carriages, and to methods for transferring a battery between battery transfer carriages and vehicles. Background Art Batteries carried by vehicles, particularly electric vehicles, are heavy and cumbersome. While passenger cars tend to have batteries which are permanently installed and charged in place, many industrial vehicles have removable batteries which are swapped out and replaced by charged replacement batteries. Handling such batteries during the unloading and loading procedure requires specialised equipment. A subset of such vehicles have batteries which slide or roll into place into a compartment in the vehicle from a battery transfer carriage. The carriage must be aligned with the compartment carefully, to allow the battery to be slid or rolled from a platform on the carriage to a batteryreceiving surface of the compartment and vice versa. One example of such a carriage is the Automatic Transfer Carriage sold by Solus Group of St. Louis, Missouri. This apparatus is designed for changing the batteries of an electric forklift truck, and it comprises a carriage body that can be mounted on a pallet truck (or another forklift truck). The pallet truck can manoeuvre the carriage body towards the forklift truck bringing it to a position at the correct lateral location and correct height to allow the battery to be extracted from the forklift truck onto the carriage platform, or vice versa. The height of the platform of a battery transfer carriage must be carefully matched to the height of the vehicle's battery compartment. Forklift batteries can typically weigh up to e.g. 3000 kg, and for a smooth transfer the battery needs the surfaces of the battery compartment and the transfer carriage platform to be aligned to within a tolerance of ± 1 mm. It is not possible to provide a battery transfer carriage having a fixed height for a given vehicle, because the height of a vehicle's battery compartment will vary over time. Where vehicles are provided with solid tyres (as is typical for industrial vehicles of many kinds) the tyre wear may cause the vehicle's height to change by 5-7 cm over the lifetime of a set of tyres. For vehicles with pneumatic tyres, the tyre pressure will affect the height, and for all such vehicles, the sheer weight of the battery can cause the height to change during the loading or unloading process. This means that the height of the battery transfer carriage needs to be carefully controlled to ensure that the battery can be safely and smoothly transferred when it is slid or rolled into the battery compartment. There is therefore a need for a battery transfer carriage that provides for improvements in the battery transfer procedure. Disclosure of the Invention There is provided a battery transfer carriage for use in transferring a battery unit to and from a vehicle, comprising: a carriage body having a front end and a rear end; a battery platform for receiving and supporting a battery unit placed thereon, the battery platform extending to the front end of the carriage body, permitting a battery unit to be transferred between the battery platform and a battery-receiving surface of a vehicle in a translational motion across the front end of the carriage body; a coupling component, disposed adjacent the front end of the carriage body, adapted to engage with a complementary component of a vehicle body to couple the carriage body to the vehicle body, with the weight of the front end of the carriage body being supported by the vehicle body; wherein when the coupling component is engaged in use, the height of the front end of the carriage body is determined by the height of the complementary component of the vehicle body. Because the battery transfer carriage is coupled to a vehicle body, with its weight at the front end supported by the vehicle body and with the height of the front end being determined by the coupling component engaged with a complementary component on the vehicle body, a perfectly matched height can be achieved easily and consistently by a mechanically simple loadbearing coupling. Preferably, the carriage body is provided with a ground-engaging support disposed rearwardly of the centre of mass of the carriage body. In this way, the weight of the carriage body will be supported at the rear by the groundengaging support, but the center of mass will cause a significant downward force to be exerted on the coupling at the front end, ensuring that the height of the front end is properly matched to the vehicle. Preferably, when the carriage body is coupled to a vehicle body, with the ground-engaging support resting on the ground, the weight of the battery transfer carriage is distributed between the vehicle body and the ground-engaging support. Preferably, the ground-engaging support has an adjustable height, whereby the height of the rear end of the carriage may be adjusted relative to the height of the front end. In this way the battery platform can be adjustably sloped between the front and rear ends. Preferably, the height of the rear end of the carriage is adjustable when the front end is mounted on and coupled to a vehicle body, between a height causing the battery platform to slope downwardly towards the front end, and a height causing the battery platform to slope downwardly away from the front end. The slope can thereby provide a mechanical advantage or gravity assistance to moving a heavy battery unit into or out of the vehicle. Preferably, the battery platform is provided with means for reducing resistance to translational movement of the battery to and from the battery platform via the front end. Preferably, the means for reducing resistance comprises a plurality of rollers provided in or on the battery platform. Preferably, the coupling component comprises a male part of a coupling, adapted to engage with a female part of a coupling provided on a vehicle body. Alternatively, the coupling component may comprise a female part of a coupling, adapted to engage with a male part of a coupling provided on a vehicle body. Preferably when the coupling comprises male and female parts, the male part comprises a projection extending outwardly to engage with the female part when the carriage body is brought towards the vehicle body. Preferably, the projection is shaped to lock the carriage body to the vehicle body when engaged. Further, preferably, the weight of the front end of the carriage body causes the projection to lock the carriage body to the vehicle body in use. Further, preferably, raising the front end of the carriage body causes the projection to be released from locking engagement. Preferably, the battery transfer carriage comprises a plurality of said coupling components each adapted to engage with a respective complementary component. Preferably, the battery transfer carriage further comprises a winch mechanism for moving a battery unit across the battery platform. Preferably, the battery transfer carriage further comprises one or more guides to ensure the battery unit remains aligned with the battery platform during translational movement. Preferably, the carriage body is configured to be stably supported on the forks of a forklift truck with the battery platform horizontal. More preferably, the carriage body is provided with horizontal channels to receive the forks of a forklift truck. Further, preferably, the channels are accessible to a forklift truck from the rear end of the carriage body, such that when lifted by a forklift truck, the front end can be engaged with a vehicle body. In another aspect there is provided a vehicle body having a battery-supporting surface for receiving a battery, the vehicle body further comprising a complementary component adapted to engage with a coupling component of a battery transfer carriage according to any preceding claim, the complementary component being positioned relative to the battery-supporting surface such that when the coupling component of the battery transfer carriage is engaged with the complementary coupling component of the vehicle body, with the weight of the front end of the battery transfer carriage supported on the vehicle body via the coupling, the battery platform of the battery transfer carriage is aligned in height with the battery-supporting surface of the vehicle. Preferably, the battery-supporting surface is provided with rollers. Preferably, the rollers of the battery supporting surface are configured to be aligned in height with corresponding rollers of the battery platform. Preferably, the complementary component comprises at least one recess adapted to receive a coupling component in the form of a projection at the front end of the battery transfer carriage. Preferably, the recess is shaped to lock the carriage body to the vehicle body when the weight of the front end of the carriage body is supported by the vehicle body. Preferably, the complementary component is positioned relative to the battery-supporting surface such that when the coupling component of the battery transfer carriage is engaged with the complementary coupling component of the vehicle body, the battery platform of the battery transfer carriage is aligned laterally with the battery-supporting surface of the vehicle. In a preferred combination, there is provided a battery transfer carriage as claimed herein, in combination with a vehicle having a vehicle body as claimed herein. In another aspect there is provided a method of transferring a battery between a battery transfer carriage and a vehicle, comprising: providing a battery transfer carriage having a battery platform and a coupling component adjacent a front end of the battery platform; providing a vehicle having a battery-receiving surface and a complementary component adjacent the battery-receiving surface which is adapted to engage with said coupling component; providing support to the front end of the battery transfer carriage to raise it to a height where the coupling component and complementary component are aligned; moving the battery transfer carriage toward the vehicle to bring the coupling component and complementary component into coupling engagement; removing said support from the front end of the battery transfer carriage so that the front end of the battery carriage is supported by the vehicle via the coupling component and complementary component with the battery platform aligned in height with the battery-receiving surface. Brief Description of the Drawings The invention will be further illustrated by the following description of embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side elevation view of a generic vehicle with a battery compartment; Fig. 2 is a perspective view of the vehicle of Fig. 1; Fig. 3 is a side elevation view of the vehicle of Fig. 1 with a battery unit installed; Fig. 4 is a cross-sectional plan view of the vehicle shown in Fig. 3; Fig. 5 is a perspective view of the vehicle shown in Fig. 3; Fig. 6 is a side elevation view of a battery transfer carriage; Fig. 7 is a top plan view of the battery transfer carriage of Fig. 6; Fig. 8 is a perspective view of the battery transfer carriage of Fig. 6; Fig. 9 is a side view of the battery transfer carriage of Fig. 6 coupled to the vehicle of Figs. 1-5; Fig. 10 is an end elevation view of the coupled battery transfer carriage and vehicle; Fig. 11 is a perspective view of the coupled battery transfer carriage and vehicle; Fig. 12 is a view similar to Fig. 9 but with an enlarged detail of the coupling; Fig. 13 is a side elevation view of the coupled battery transfer carriage and vehicle, during an unloading operation; Fig. 14 is a perspective view of the coupled battery transfer carriage and vehicle, during an unloading operation; Fig. 15 is a side elevation view of the coupled battery transfer carriage and vehicle, when a battery unit is fully unloaded from the vehicle onto the battery transfer carriage; Fig. 16 is a perspective view of the coupled battery transfer carriage and vehicle, when a battery unit is fully unloaded from the vehicle onto the battery transfer carriage; Fig. 17 is a perspective view of the coupled battery transfer carriage and vehicle, after the battery unit has been lifted off the battery transfer carriage; Fig. 18 is a perspective view of the coupled battery transfer carriage and vehicle, after a replacement battery unit has been loaded onto the battery transfer carriage in preparation for loading into the vehicle; and Fig. 19 is a side view of the coupled battery transfer carriage and vehicle as shown in Fig. 18, ready to load the battery unit into the vehicle. Detailed Description of Preferred Embodiments In Fig. one there is indicated generally at 10, a portion of a generic vehicle with a battery compartment 12. The generically illustrated portion of a vehicle 10 could form part of any suitable vehicle having a large battery compartment for receiving a replaceable battery unit, including but not limited to industrial vehicles such as forklift trucks, tracked vehicles, tugs, tractors, mobile elevated work platforms, excavators, skid-steer vehicles, dumpers, or indeed any vehicle that can be electrified and which requires a battery change. As best seen in Fig. 2, the battery compartment 12 is shown empty in Figs. 1 and 2. The battery compartment takes the form of a large cuboid void, having at its base a battery supporting surface 14 provided with a plurality of rollers 16 to facilitate rolling a battery unit in or out in a sliding motion, together with rollers 18 on either side of the entrance to the battery compartment, and similar rollers (not shown) at the inner end of the compartment, which assist in guiding the battery unit straight within the battery compartment 12. A pair of recesses 20 are provided adjacent to the battery supporting surface 14 at its external edge, i.e. at the opening at the side of the vehicle. These recesses, as explained further below, form one half of a coupling system, allowing a battery transfer carriage to be coupled to the side of the vehicle. Figs. 3-5 show the portion of vehicle 10 when a battery unit 22 is installed, in side elevation in Fig. 3, in sectional plan view in Fig. 4, and in perspective view in Fig. 5. As seen in Fig. 4, the battery unit 22 is a large cuboid-shaped unit which substantially fills the battery compartment across the full width of the vehicle, and which is filled with a number of individual battery cells 24. The details of operation of the battery unit, and the type of battery cell, are immaterial for the purposes of this invention, which is applicable to the transfer of any kind of battery to and from a vehicle in a lateral motion. Fig. 4 also shows the side rollers 18 located at either end of the battery compartment and a number of rollers 16 on the battery-receiving surface or base of the battery compartment. While the battery unit 22 substantially fills the battery compartment, the rollers allow the battery unit 22 to be slid easily into the compartment with minimal resistance and to be pulled out of the compartment in a sliding motion. Not shown in Figs. 3-5 are extraneous details such as the remaining vehicle components which would be visible in a cross-sectional view, the electrical connections to the battery, or a door which would normally be provided to cover and enclose the battery compartment when the battery unit is in place. Figs. 6, 7 and 8 show a battery transfer carriage, indicated generally at 30, in side elevation, top plan view and perspective view, respectively. The battery transfer carriage 30 has a carriage body 32 with a front end 34 and a rear end 36. The carriage body 32 provides a battery platform for receiving a battery unit of the type shown in Figs. 3-5. Specifically the battery unit is received on rollers 38 provided in the upper surfaces of the carriage body 32. Along either side of the carriage body a series of side guards 40 with rollers 42 assist in guiding a battery unit in an aligned manner on and off the front end 34 of the carriage body 32 with a sliding lateral movement. At the front end 34 of the carriage body a pair of projections 44 project in the frontward direction. These projections are coupling components which are adapted and designed to engage with complementary components such as the recesses 20 in the vehicle body. Each projection 44 has a groove 58 on its underside which is dimensioned to receive a lip at the front edge of the corresponding recess to act as a hook providing a locking engagement between the projection 44 and the recess 20, as described further below. At the rear end 36 of the carriage body 32, a ground-engaging leg 46 is provided. The leg 46 can be extended and retracted by means of any suitable mechanism, such as mechanically, electrically, hydraulically or pneumatically. In the illustrated embodiment, a handle mechanism 48 acts on a geared mechanical drive to raise or lower the leg 46 relative to the carriage body. A winch 50 is also provided at the rear end 36. The winch, which in this embodiment is operated mechanically by a separate handle 52 but could be operated by any other suitable mechanism, allows a spooled tether, wire or strap to be extended and attached to a battery unit, with the winch providing mechanical advantage in pulling the battery unit from the vehicle onto the battery platform of the carriage body 32. On the underside of the carriage body, a pair of fork sleeves 54 (one of which is visible in Fig. 8) are provided. The fork sleeves may receive the forks of a lift truck, such as a forklift truck or a pallet truck, for manoeuvring the carriage body into position and away from a vehicle, and raising the carriage body to a suitable height. Figs. 9-11 show the battery transfer carriage 30 coupled to the vehicle body 10, prior to removal of a battery unit 22. The battery transfer carriage is coupled in place as follows. First, the battery transfer unit is picked up by a lift truck (not shown), e.g. a forklift truck or pallet truck which engage the battery transfer unit, preferably using the fork sleeves. The lift truck manoeuvres the battery transfer carriage perpendicularly towards the side of the vehicle 10, and adjusts the height of the transfer carriage so that the projections 44 are vertically aligned with the recesses 20 (Fig. 1). Absolute precision is not needed to match the height of the projections to the recesses, as the recesses are taller than the projections, so there is some tolerance when inserting the projections into the recesses to initiate the coupling. When the projections 44 are aligned laterally and vertically with the recesses 20, the battery transfer carriage is pushed home against the vehicle side, with the front end of the carriage body meeting the side of the vehicle, at which point the lip along the front lower edge of the recess is aligned with the groove on the underside of the projection. Beyond the lip within the recess, there is space for the portion of the projection forward of the groove to drop into place. Fig. 12 is a view similar to Fig. 9, but with an enlarged view of the coupling, seen in cross-section through one projection 44 and recess 20. It can be seen that a front lip 56 at the lower outer edge of the recess 20 fits snugly into and is engaged with a groove 58 on the underside of the projection. The ground-engaging leg 46 can then be extended until it is close to or touching the ground, and the lift truck then lowers its forks until the weight of the battery transfer carriage 30 is fully supported at the rear end 36 by the ground-engaging leg 46, and at the front end 34 by the interaction between the projections and recesses, in other words supported by the vehicle via the coupling. Once the weight of the battery transfer carriage has been removed from the forks, the lift truck can disengage the forks from the fork sleeves and can be driven away, leaving the battery transfer carriage coupled in place to the side of the vehicle. Because the only point of ground contact, once the coupling operation is complete, is the ground-engaging leg 46, as seen in Fig. 9 and 10, and because the centre of mass of the battery transfer carriage is forward of this point, the centre of mass exerts a rotational moment force forward about the ground contact point. This results in the weight of the front end of the carriage being entirely carried by the vehicle, or more specifically by the coupling and primarily by the area of contact between the projections 44 and the lips of the recesses 20 on which they rest. Due to those lips being located in respective grooves on the underside of the projections, the projections are hooked onto the side of the vehicle and lock the battery transfer carriage in place to prevent it from disengaging accidentally or even under a quite strong rearward force e.g. when moving a heavy battery unit across the coupling. With the coupling component (projections 44) engaged with the complementary components (recesses 20) the battery platform of the battery transfer carriage is exactly and precisely aligned in height with the battery-receiving surface of the vehicle's battery compartment. It will be appreciated that this is guaranteed and is achieved consistently each time automatically when the coupling engages, regardless of the precise height of the vehicle due to tyre wear, suspension issues, vehicle load issues, uneven ground, and so forth. Simply engaging the coupling and letting the front end of the battery transfer carriage come to rest with the weight of the front end of the battery transfer carriage on the vehicle, ensures matching heights. Furthermore, if the vehicle height changes at all during the procedure (due to the addition or removal of the significantly heavy battery during the loading / unloading procedure for instance), the front end of the battery transfer carriage will rise or fall along with the vehicle, maintaining an exact correspondence in height between the surfaces on which the battery unit moves. As seen in Fig. 9, the ground-engaging leg 46 may be adjusted to lower the rear end of the battery transfer carriage 30 relative to the front end, so that the battery platform slopes downwardly. The downward slope is shown in this case as a small amount, e.g. a few degrees or less, which is sufficient to aid in moving the battery onto and along the battery platform of the battery transfer carriage. With the level adjusted, as shown in Figs. 13 and 14, the winch 50 can then be used to attach a tether 52 to the battery unit's exposed face, and the battery unit 22 is winched out of the vehicle and onto the battery platform of the battery transfer carriage, with the slight downward slope assisting in the transfer in a controlled manner. It should be emphasized that the winch is not essential in many cases. Due to the rollers along the battery-receiving surface of the vehicle's battery compartment, and the rollers on the battery platform of the battery transfer carriage, the battery can often be pulled clear by a single person despite its weight. Rollers could be substituted by low-friction skid plates or other means for reducing resistance to sliding. Referring back to Fig. 8 and Fig. 12, a cam-operated spring-loaded latch 60 is provided at the front end of the battery platform, which is depressed by the battery unit moving over it, and which springs back to the position shown in Fig. 8 after the battery unit has fully passed onto the battery platform, to prevent the battery unit from accidentally rolling off the platform. A release handle 62 at the rear end of the battery transfer carriage can be used to retract the latch 60 when it is time to load a battery unit from the battery platform into a vehicle. Figs. 15 and 16 show the battery unit 22 fully unloaded from the vehicle 10 onto the battery transfer carriage 30. Fig. 17 shows the battery unit 22 removed from the battery transfer carriage 30 (having been lifted off using a forklift, a hoist, or other suitable means), and Fig. 18 shows a charged replacement battery unit 22A after having been lifted and placed onto the battery transfer carriage 30 ready for loading into the vehicle. As seen in Fig. 19, the ground-engaging leg 46 may then be extended to raise the rear end 36 of the carriage relative to the front end 34, reversing the slope direction so that there is a downward slope from the rear end to the front end of the battery transfer carriage. By using the handle 62 to retract the latch 60 and then gently raising the rear end, the battery unit 22A can be pushed easily forward into the vehicle's battery compartment and pushed fully home, with a smooth transition across the gap between the battery platform and the battery-receiving surface of the battery compartment. While the illustrated embodiment uses a lift truck or other external agent to raise the front end of the carriage body to the height required to engage the coupling, it will be appreciated that one could equally provide a battery carriage supported at the front end on a retractable ground support providing a height adjustment, so that the ground support could be initially adjusted to allow the coupling to take place, and then the ground support at the front end retracted and lifted away from the ground to allow the coupling to take the weight at the front end. Such an embodiment could be made mobile by fitting the front and rear ground supports with wheels, which would preferably be lockable to prevent movement when the battery transfer carriage is in position during any loading or unloading procedure. Such an embodiment could also be self-powered to drive under operator control, or autonomously, into position. Also, while the illustrated embodiment uses a height-adjustable ground-engaging leg, it would also be possible to support the rear end throughout on a pallet truck or forklift truck, or similar, and to adjust the height using this support means. The invention is not limited to the embodiments described herein which may be modified or varied without departing from the scope of the claims.

Claims

1. A battery transfer carriage for use in transferring a battery unit to and from a vehicle, comprising:a carriage body having a front end and a rear end;a battery platform for receiving and supporting a battery unit placed thereon, the battery platform extending to the front end of the carriage body, permitting a battery unit to be transferred between the battery platform and a battery-receiving surface of a vehicle in a translational motion across the front end of the carriage body;a coupling component, disposed adjacent the front end of the carriage body, adapted to engage with a complementary component of a vehicle body to couple the carriage body to the vehicle body, and to bear the weight of the front end of the carriage body;wherein when the coupling component is engaged in use, the front end of the carriage body is supported by the coupling component, and the height of the front end of the carriage body is determined by the height of the complementary component of the vehicle body.

2. A battery transfer carriage according to claim 1, wherein the carriage body is provided with a ground-engaging support disposed rearwardly of the centre of mass of the carriage body.

3. A battery transfer carriage according to claim 2, wherein when the carriage body is coupled to a vehicle body, with the ground-engaging support resting on the ground, the weight of the battery transfer carriage is distributed between the vehicle body and the groundengaging support.

4. A battery transfer carriage according to claim 2 or 3, wherein the ground-engaging support has an adjustable height, whereby the height of the rear end of the carriage may be adjusted relative to the height of the front end.

5. A battery transfer carriage according to claim 4, wherein the height of the rear end of the carriage is adjustable between a height causing the battery platform to slope towards the front end, and a height causing the battery platform to slope away from the front end.

6. A battery transfer carriage according to any preceding claim, wherein the battery platform is provided with means for reducing resistance to translational movement of the battery to and from the battery platform via the front end.

7. A battery transfer carriage according to claim 6, wherein the means for reducing resistance comprises a plurality of rollers provided in or on the battery platform.

8. A battery transfer carriage according to any preceding claim, wherein the coupling component comprises a male part of a coupling, adapted to engage with a female part of a coupling provided on a vehicle body.

9. A battery transfer carriage according to any of claims 1-7, wherein the coupling component comprises a female part of a coupling, adapted to engage with a male part of a coupling provided on a vehicle body.

10. A battery transfer carriage according to claim 8 or 9, wherein the male part comprises a projection extending outwardly to engage with the female part when the carriage body is brought towards the vehicle body.

11. A battery transfer carriage according to claim 8, wherein the projection is shaped to lock the carriage body to the vehicle body when engaged.

12. A battery transfer carriage according to claim 9, wherein the weight of the front end of the carriage body causes the projection to lock the carriage body to the vehicle body in use.

13. A battery transfer carriage according to claim 10, wherein raising the front end of the carriage body causes the projection to be released from locking engagement.

14. A battery transfer carriage according to any preceding claim, comprising a plurality of said coupling components each adapted to engage with a respective complementary component.

15. A battery transfer carriage according to any preceding claim, further comprising a winch mechanism for moving a battery unit across the battery platform.

16. A battery transfer carriage according to any preceding claim, further comprising one or more guides to ensure the battery unit remains aligned with the battery platform during translational movement.

17. A battery transfer carriage according to any preceding claim, wherein the carriage body is shaped to be stably supported on the forks of a forklift truck with the battery platform horizontal.

18. A battery transfer carriage according to claim 17, wherein the carriage body is provided with horizontal channels to receive the forks of a forklift truck.

19. A battery transfer carriage according to claim 18, wherein the channels are accessible to a forklift truck from the rear end of the carriage body, such that when lifted by a forklift truck, the front end can be engaged with a vehicle body.

20. A vehicle body having a battery-supporting surface for receiving a battery, the vehicle body further comprising a complementary component adapted to engage with a coupling component of a battery transfer carriage according to any preceding claim, the complementary component being positioned relative to the battery-supporting surface such that when the coupling component of the battery transfer carriage is engaged with the complementary coupling component of the vehicle body, with the weight of the front end of the battery transfer carriage supported on the vehicle body via the coupling, the battery platform of the battery transfer carriage is aligned in height with the battery-supporting surface of the vehicle.

21. A vehicle body according to claim 20, wherein the battery-supporting surface is provided with rollers.

22. A vehicle body according to claim 21, wherein the rollers of the battery supporting surface are configured to be aligned in height with corresponding rollers of the battery platform.

23. A vehicle body according to any of claims 20-22, wherein the complementary component comprises at least one recess adapted to receive a coupling component in the form of a projection at the front end of the battery transfer carriage.

24. A vehicle body according to claim 23, wherein the recess is shaped to lock the carriage body to the vehicle body when the weight of the front end of the carriage body is supported by the vehicle body.

25. A vehicle body according to any of claims 20-24, wherein the complementary component is positioned relative to the battery-supporting surface such that when the coupling component of the battery transfer carriage is engaged with the complementary coupling component of the vehicle body, the battery platform of the battery transfer carriage is aligned laterally with the battery-supporting surface of the vehicle.

26. A battery transfer carriage according to any of claims 1-19, in combination with a vehicle having a vehicle body according to any of claims 20-25.

27. A method of transferring a battery between a battery transfer carriage and a vehicle, comprising:providing a battery transfer carriage having a battery platform and a coupling component adjacent a front end of the battery platform;providing a vehicle having a battery-receiving surface and a complementary component adjacent the battery-receiving surface which is adapted to engage with said coupling component;providing support to the front end of the battery transfer carriage to raise it to a height where the coupling component and complementary component are aligned;moving the battery transfer carriage toward the vehicle to bring the coupling component and complementary component into coupling engagement;removing said support from the front end of the battery transfer carriage so that the front end of the battery carriage is supported by the vehicle via the coupling component and complementary component with the battery platform aligned in height with the battery-receiving surface.17

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