GB2553541A

GB2553541A - Battery pack

Info

Publication number: GB2553541A
Application number: GB1615195.3A
Authority: GB
Inventors: Smith Richard; Simonavicius Matas
Original assignee: Arrival Ltd
Current assignee: Arrival UK Ltd
Priority date: 2016-09-07
Filing date: 2016-09-07
Publication date: 2018-03-14
Anticipated expiration: 2036-09-07
Also published as: GB201615195D0; GB2553541B

Abstract

An electric vehicle battery pack includes a plurality of battery modules 41 spaced apart from each other within a battery box that comprises a base panel 34, a plurality of side wall panels 35 and a lid 27. The battery modules are supported so as to be spaced from the base panel and define a space therebetween. A thermal control unit 43, which may include a fan 45 and an air conditioning unit 46, circulates air through the battery box, through the space between the battery modules and the base panel, and the spaces between the battery modules. The temperature of the circulated air is controlled by the thermal control unit, which may cool or heat the circulated air depending on a temperature sensed within the battery box. An inlet vent aperture 39 extends through a lower portion of a side wall panel and an outlet vent aperture 40 extends through an upper portion of the side wall panel. The thermal control unit may be disposed on the outside of the battery box with an exhaust port 47 of the unit connected to the inlet vent aperture and an intake port 48 of the unit connected to the outlet vent aperture.

Description

(71) Applicant(s):

Arrival Limited

Unit 2, Southam Road, Banbury, Oxfordshire, OX16 2DJ, United Kingdom (72) Inventor(s):

Richard Smith Matas Simonavicius (74) Agent and/or Address for Service:

Venner Shipley LLP

200 Aldersgate, LONDON, EC1A4HD,

United Kingdom (51) INT CL:

B60L 11/18 (2006.01) H01M 10/613 (2014.01) (56) Documents Cited:

EP 2368740 A1 EP 2078628 A2

EP 2075873 A1 EP 1153803 A2

US 5490572 A (58) Field of Search:

INT CL B60L

Other: ONLINE: WPI, EPODOC (54) Title of the Invention: Battery pack

Abstract Title: Temperature controlled electric vehicle battery pack (57) An electric vehicle battery pack includes a plurality of battery modules 41 spaced apart from each other within a battery box that comprises a base panel 34, a plurality of side wall panels 35 and a lid 27. The battery modules are supported so as to be spaced from the base panel and define a space therebetween. Athermal control unit 43, which may include a fan 45 and an air conditioning unit 46, circulates air through the battery box, through the space between the battery modules and the base panel, and the spaces between the battery modules. The temperature of the circulated air is controlled by the thermal control unit, which may cool or heat the circulated air depending on a temperature sensed within the battery box. An inlet vent aperture 39 extends through a lower portion of a side wall panel and an outlet vent aperture 40 extends through an upper portion of the side wall panel. The thermal control unit may be disposed on the outside of the battery box with an exhaust port 47 of the unit connected to the inlet vent aperture and an intake port 48 of the unit connected to the outlet vent aperture.

14,15

/12

2/12

4/12

5/12

6/12

7/12

8/12

14/15

•si9/12

/12

12/12

g 8 '*5anS>'^c a

Battery Pack

Technical Field

The present invention relates to a battery pack for use in an electric vehicle.

Background

The drive for more fuel efficient and environmentally friendly transport solutions is seeing an increasing level of development in the field of electric vehicles. Such vehicles include not only passenger vehicles for personal transport, but also commercial vehicles such as buses and trucks. Such electric vehicles (EVs) include pure battery electric vehicles (BEVs) powered by batteries alone, and range extender electric vehicles (REEVs) which also include a small internal combustion engine (ICE) to generate electricity to supplement the battery power source. All such EVs include battery packs for supplying electrical power to the electric drive motor(s). Such battery packs typically comprise a number of connected battery modules contained within a battery box, conventionally a metallic battery box, for example made of steel or aluminium.

In passenger car EVs, the battery packs are contained within the body of the vehicle and so are generally not exposed to ambient conditions such as temperature fluctuations, rain, dirt and dust or impact from debris thrown up from the road. However, in commercial vehicles, such as delivery trucks, the battery packs may be mounted to the vehicle chassis rails and so may be at least partially exposed to such environmental factors in vehicle use.

Summary

In accordance with embodiments of the invention, there is provided a battery pack for use in an electric vehicle comprising a battery box comprising a body portion comprising a base and a plurality of side walls defining an interior space and an upper opening, and a lid secured over the upper opening to close the box portion, a plurality of battery modules spaced from each other within the body portion, support means supporting the battery modules so as to be spaced from the base panel to define a space between the battery modules and the base panel, and a thermal control unit configured to circulate air through the battery box through the space between the battery modules and the base panel, and between the battery modules, and to control the temperature of the circulated air.

The support means may comprise a floor panel parallel to and spaced from the base panel to define a passage between the floor panel and the base panel, the floor panel including a plurality of apertures extending therethrough to fluidly communicate the passage with the remaining interior space of the box portion.

The apertures in the floor panel may be aligned with the spaces between the individual battery modules.

A side wall of the box portion may include an inlet vent aperture extending therethrough proximate a lower portion thereof and communicating with the space between the support means and the base panel, and an outlet vent aperture extending therethrough proximate an upper portion thereof, and communicating with the remaining interior space of the box portion, wherein the thermal control unit maybe configured to circulate air out of the box portion through the outlet vent aperture and into the box portion through the inlet vent aperture.

The thermal control unit may be disposed on the outside of the battery box over the inlet and outlet vents.

The area of the outlet vent aperture may be substantially the same as the area of the inlet vent aperture.

The thermal control unit may be detachably mounted to the outside of the battery box by releasable fastening elements.

At least one of the base wall, side walls and lid may comprise a composite panel comprising a core having a plurality of cavities therein and first and second skins respectively bonded to first and second opposite sides of the core. All of the base, side walls and lid may comprise the composite panels. The core may comprise a honeycomb structure. The honeycomb core may be made of polypropylene and the skins comprise glass fibre reinforced polypropylene sheets.

At least two out of the base and side walls may be integrally formed from a single composite panel.

-3The side wall panels, base panel and lid may include an EMC shielding. The EMC shielding lining may comprise a woven fabric of metallic fibres. The EMC shielding may comprise a lining on the inside surfaces of the side wall panels, base panel and lid, and/or may comprise a layer of material embedded within at least one of the side wall panels, base panel and lid.

An airtight seal may be formed at the junction where each side panel, base panel and the lid abut.

The battery pack may further comprise a first temperature sensor disposed within the box portion, and a controller connected to the first temperature sensor and thermal control unit and configured to control operation of the thermal control unit in dependence on a signal received from the first temperature sensor.

The controller may be configured to control the thermal control unit to cool the circulated air if the sensed temperature is above a first pre-determined threshold temperature, and may be configured to control the thermal control unit to heat the circulated air if the sensed temperature is below a second pre-determined threshold temperature.

The battery pack may further comprise a second temperature sensor connected to the controller, and wherein the controller may be configured to control operation of the thermal control unit in dependence on signals received from one or both of the first and second temperature sensors.

The first temperature sensor may be positioned proximate the inlet vent aperture to measure the temperature of air flowing into the battery box, and the second temperature sensor maybe positioned proximate the outlet vent aperture to measure the temperature of air flowing out of the battery box.

The controller may be configured to determine a temperature difference between a temperature measured by the first and second temperature sensors and to control the thermal control unit in dependence on the determined temperature difference.

-4The controller may be configured to control the thermal control unit to operate whilst the difference between temperatures sensed by the first and second temperature sensors exceeds a predetermined threshold temperature difference.

The battery pack may further comprise a third temperature sensor disposed within the battery box and spaced from the inlet and outlet vent apertures, and wherein the controller may be configured to control the thermal control unit in dependence on signals received from the first, second and third temperature sensors.

Each battery module may comprise a respective module temperature sensor, and the controller may be configured to control operation of the thermal control unit in dependence upon signals received from the first temperature sensor and the module temperature sensors.

The controller may comprise a first controller, and the battery pack may further comprise a second controller connected to each battery module, and wherein the first controller may be configured to control operation of the thermal control unit in dependence on signals received from the second controller.

The second controller may be configured to determine the temperature of each battery module and to determine a range of module temperatures, and the first controller may be configured to operate the thermal control unit when the range of module temperatures exceeds a predetermined temperature difference.

The battery pack may comprise positive and negative power output connectors, and respective positive and negative contactors to control the connection between the battery modules and the respective positive and negative power output connectors, wherein the first or the second controller may be connected to the positive and negative contactors and configured to control operation of the positive and negative contactors.

The present invention also provides a method of controlling the temperature within a battery pack for use in an electric vehicle comprising a battery box comprising a body portion comprising a base and a plurality of side walls defining an interior space and an upper opening, and a lid secured over the upper opening to close the box portion, a plurality of battery modules spaced from each other within the body portion, and support means supporting the battery modules so as to be spaced from the base panel

-5to define a space between the battery modules and the base panel, and a thermal control unit, the method comprising operating the thermal control unit to circulate air through the battery box through the space between the battery modules and the base panel, and between the battery modules, and controlling the temperature of the circulated air.

The support means may comprise a floor panel parallel to and spaced from the base panel to define a passage between the floor panel and the base panel, the floor panel including a plurality of apertures extending therethrough to fluidly communicate the passage with the remaining interior space of the box portion, and the method may comprise circulating the air through the passage the through the apertures in the floor panel.

The method may comprise circulating the air into the box portion through an inlet vent aperture extending through a side wall of the box portion proximate a lower portion thereof and communicating with the space between the support means and the base panel, and out of the box portion through an outlet vent aperture extending through a side wall of the box portion proximate an upper portion thereof and communicating with the remaining interior space of the box portion.

The method may comprise disposing the thermal control unit on the outside of the battery box over the inlet and outlet vents.

The method may comprise providing a seal between the box portion and the lid to form an air-tight seal between the box portion and the lid.

The method may comprise providing at least one of the base wall, side walls and lid from a composite panel comprising a core having a plurality of cavities therein and first and second skins respectively bonded to first and second opposite sides of the core.

The method may comprise providing all of the base, side walls and lid as the composite panels.

The method may comprise detecting a temperature within the box portion using a first temperature sensor disposed within the box portion, and controlling operation of the thermal control unit using a controller connected to the first temperature sensor and

-6the thermal control unit, in dependence on a signal received from the first temperature sensor.

The battery pack may further comprise a second temperature sensor connected to the 5 controller, and the method may comprise controlling operation of the thermal control unit in dependence on signals received from one or both of the first and second temperature sensors.

The method may comprise measuring the temperature of air flowing into the battery 10 box by the first temperature sensor positioned proximate the inlet vent aperture, and measuring the temperature of air flowing out of the battery box by the second temperature sensor positioned proximate the outlet vent aperture.

The method may comprise determining a temperature difference between a 15 temperature measured by the first and second temperature sensors and controlling the thermal control unit in dependence on the determined temperature difference.

The method may comprise controlling the thermal control unit to operate whilst the difference between temperatures sensed by the first and second temperature sensors exceeds a predetermined threshold temperature difference.

The battery pack may further comprise a third temperature sensor disposed within the battery box and spaced from the inlet and outlet vent apertures, and the method may comprise controlling the thermal control unit in dependence on signals received from the first, second and third temperature sensors.

Each battery module may comprise a respective module temperature sensor, and the method may comprise controlling operation of the thermal control unit in dependence signals received from the first temperature sensor and the module temperature sensors.

The controller may comprise a first controller, and the battery pack may further comprise a second controller connected to each battery module, and the method may comprise the first controller controlling operation of the thermal control unit in dependence on signals received from the second controller.

-ΊThe method may comprise the second controller determining the temperature of each battery module and determining a range of module temperatures, and the first controller operating the thermal control unit when the range of module temperatures exceeds a predetermined temperature difference.

The battery pack may comprise positive and negative power output connectors, and respective positive and negative contactors to control the connection between the battery modules and the respective positive and negative power output connectors, and the method may comprise the first or the second controller being connected to the positive and negative contactors and controlling operation of the positive and negative contactors.

Brief Description of the Drawings

Embodiments of the present invention will now be described, byway of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a schematic view of a chassis and drive train of a commercial electric 20 vehicle including a battery pack of an embodiment of the invention;

Fig.2 shows a perspective view of a battery box of a battery pack of an embodiment of the invention with a lid shown detached and spaced from the box body;

Fig. 3 shows an exploded perspective view of a composite panel comprising the walls of the battery box of Fig. 2;

Fig. 4 shows a cross-sectional view of the battery box of Fig. 2 taken along the line X-X shown in Fig. 2, but with the lid secured to the box body;

Fig. 5 shows a cross-sectional view of an edge portion another exemplary battery box of a battery pack of an embodiment of the invention;

Fig. 6 shows a cross-sectional view of an edge portion yet another exemplary battery 30 box of a battery pack of an embodiment of the invention;

Fig. 7 shows a perspective view of a battery pack of an embodiment of the invention, including the battery box of Fig. 2;

Fig. 8 shows a cross-sectional view of the battery pack of Fig. 7 taken along the line Y-Y shown in Fig. 7, but with the lid secured to the box body; and

Fig. 9 shows a schematic system diagram of the battery pack of Figs. 7 and 8.

-8Detailed Description

Fig. l shows a chassis 10 of an exemplary commercial REEV, and comprises a pair of chassis rails n to which are mounted a front drivetrain module 12, a rear drivetrain module 13, first and second high voltage battery packs 14,15 and a range extender unit

16.

The front drivetrain module 12 comprises an electric motor 17 and a gearbox 18 which drive front wheels 19 mounted on suspension arms 20. Similarly, the rear drivetrain module 13 comprises an electric motor and a gearbox (not shown - although these are advantageously the same components and configuration as those of the front drivetrain module) which drive rear wheels 23 mounted on suspension arms 24.

The first high voltage battery pack 14 is mounted between the chassis rails 11 and the second high voltage battery pack 15 is mounted on a side of the chassis 10 on an outside of a right chassis rail 11. The range extender unit 16 is mounted on an opposite side of the chassis 10 to the second battery pack 15, on an outside of a left chassis rail 11.

Fig 2 shows an exemplary battery box 25 of the high voltage battery packs 14,15 and comprises a box body 26 and a box lid 27. The battery box 25 of this exemplary embodiment is constructed of a plurality of composite sandwich panels 28, shown in more detail in Fig. 3. Each panel 28 comprises a core 29 formed as a honeycomb structure defining a plurality of cavities 30. Skins 31 are bonded to the major surface on either side of the core 29. The core 29 is formed of polypropylene. The skins 31 are formed of fibreglass fibres embedded in polypropylene.

The lid 27 is secured to the body 26 by mechanical fasteners (not shown), such as threaded bolts, which may be received in threaded inserts (not shown) embedded within the respective box panel 28. In the exemplary embodiment shown, a sealing element 32 is advantageously provided between the box body 26 and the lid 27 to make a seal between the body 26 and the lid 27 when the lid 27 is secured to the body 26. The sealing element 32 may comprise a gasket and may be made of any suitable material, such as a compressible material such as rubber.

A portion of the battery box 25 is advantageously provided with an EMC protective shielding material 33. This maybe provided as an EMC protective lining and may be provided on an inner surface of the battery box 25. In the exemplary embodiment

-9shown, this comprises a woven fabric sheet of metallic fibres, such as fine steel fibres. However, other forms of EMC lining maybe provided within the scope of the invention, such as a coating of conductive paint, or a plasma zinc coating on the inner surface of the battery box. In use, the EMC protective lining serves to shield any electromagnetic fields generated by battery modules within the battery box to stop them affecting any other electronic components in the rest of the vehicle. Both the box body 26 and lid 27 comprise such EMC protective lining 33, which may be provided on their inner surfaces. In order for the EMC protective lining 33 to be optimally effective, and to optimally act as a faraday cage, an EMC protective lining 33a on the box body 26 is electrically conductively connected to an EMC protective lining 33b provided on the inner surface of the lid 27.

It can be seen from the cross-sectional view of Fig. 4 that the box body 26 comprises a base panel 34 and side wall panels 35. It can also be seen that the box body 26 includes a floor panel 36 parallel to and spaced from the base panel 34 which defines a passage 37 between the base panel 34 and the floor panel 36. The floor panel 36 includes a plurality of vent holes 38 communicating the passage 37 with the remaining interior space of the box body 26. The floor panel 36 is preferably made of the same sandwich panel 28 material as the base panel 34 and side wall panels 35 described above with reference to Fig. 3.

One side wall panel 35 includes an inlet aperture 39 near the bottom edge which communicates with the passage 37, and an outlet aperture 40 towards the top edge. Vent holes 38 and the inlet and outlet apertures 39,40 are to enable air circulation within the battery box 25 as will be described hereafter. The inlet and outlet apertures 39, 40 maybe the same shape or different shapes (as shown in Fig. 2) within the scope of the invention. Advantageously, both the inlet and outlet apertures 39,40 are of substantially the same area, that is the same “surface” area, occupying the substantially the same area of the respective side wall panel 35 in which they are provided. This is to help towards preventing an imbalance or undesirable restrictions in air flow out of and into the battery box, as will be described hereafter.

An advantage of constructing the battery box 25 of the battery packs 14,15 of an embodiment of the invention of composite panels 28 comprising a polypropylene core

29 with polypropylene fibre reinforced skins 31, as described above, is that the panels maybe easily shaped during manufacture. This can be done by heating the panel 28

- 10 to soften the polypropylene and then the panel 28 can be bent to the desired angle and held in position until the panel 28 cools and the polypropylene hardens again. As such, a plurality of the side wall panels 35 and/or the base panel 34 may be formed as a single composite panel 28. For example, all side wall panels 35 may be made from one single composite panel 28 with a separate composite panel 28 for the base panel 34 bonded to the bottom edge of the side wall panels 35. Alternatively, two opposite site wall panels 35 and the base panel 34 may be made from one single composite panel 28 with separate composite panels 28 for the two remaining side wall panels 35 bonded to the side edges of the integral base and side wall panel component.

An advantage of forming at least two of the box panels from one integral composite panel is that the number of panel joins is reduced. This helps in ensuring the resulting battery box 25 is effectively sealed from ambient conditions as it reduces the number of joins where the seal between separate panels may leak and compromise the box integrity. Prevention of ingress of moisture and dust into the battery box 25 is advantageous as such ingress can be detrimental to sensitive electrical and electronic components of the battery pack 14,15 (described in more detail below). This is particularly relevant to the use of the battery pack 14,15 in a commercial vehicle in which, as described above, the second battery pack 15 is on the outside of the vehicle chassis 10, and the first battery pack 14 is mounted between the chassis rails 11. Both such locations of battery packs 14,15 are exposed to such potentially damaging environmental conditions. Also, maintaining a substantially contaminant-free environment within the battery box 25 helps in controlling the temperature and humidity within the battery box 25 of the battery pack 14,15 having a thermal control unit (described in more detail below) as it helps towards preventing cooler or hotter ambient air entering the battery box 25 and affecting the internal temperature. It also helps towards preventing moisture in ambient air affecting the humidity within the battery packs 14,15. Such construction also means the number of cutting steps, and separate components used in the box manufacture is reduced, simplifying manufacture and thereby reducing manufacturing cost and time. Such panels, which may be constructed of a polypropylene honeycomb core with fibreglass polypropylene reinforced skins, are also a relatively cost-effective material from which to construct the battery boxes, compared to other known lightweight materials such as carbon fibre for example. Also, carbon fibre is much more difficult to use in manufacture and to shape.

- 11 A further advantage of the above-described composite panel battery box 25 construction is that the composite panel 28 material includes a large number of cavities 30 within the core 29 which makes the composite panels good thermal insulators. This further helps in temperature control within the battery pack 14,15 as it reduces the impact of ambient temperature affecting the internal battery pack 14,15 temperature. This has yet further importance in colder climates since EV batteries are generally unable to be as effectively charged when below zero degrees Celsius and so a thermally insulating box construction is beneficial in helping avoid excessively low battery temperature.

A further advantage of the above-described exemplary composite panel battery box 25 construction is that the composite panel 28 material is of a lighter weight than conventional battery boxes made from, for example, metal such as steel. For example, a battery box of approximate dimensions 1200mm (length) x 600mm (width) x 400mm (height) made from conventional grade sheet steel would weigh around 70 kg, whereas an equivalent size battery box made of composite panels 28 as described above, would weigh around 15 kg, a weight difference of almost 80%. The composite panel 28 weighs around 5kg per square metre. Weight reduction is a key factor in increasing fuel economy of vehicles and is particularly important in the context of EVs to maximise vehicle efficiency and vehicle range on a given battery charge, and in reducing the battery power needed to propel the vehicle.

A yet further advantage of the above-described composite panel battery box 25 construction is that the composite panel 28 material is easy to repair if physical damage is sustained in use. This is beneficial since, as mentioned above, in use in a commercial vehicle, the battery box 25 is often mounted on the outside of the vehicle chassis 10 and so is exposed to debris which may be thrown up from the road. Damage to the skins 31 can be repaired by filling using a polypropylene gun, or if a section of the composite panel 28 needs replacing, a section can be cut out and a replacement section cut to size and bonded in place using a polypropylene gun or other suitable bonding agent.

Fig. 5 shows a cross-section through a portion of another exemplary battery box 25 of a battery pack of an embodiment of the invention, showing another exemplary means of securing the lid 27 to the box body 26. Like features with the battery box shown in Figs.

2 and 4 retain the same reference numerals. In the embodiment shown in Fig. 5, the sealing element 32 is provided around the top edge of the side wall panel 35 and the lid

- 12 27- A closure element in the form of an angle bracket 49 is secured around the join between the edge of the lid 27 and the upper edge of the side wall panel 35 to secure the lid 27 to the box body 26. Mechanical fasteners (not shown) may secure the angle bracket 49 in place to the box body 26 and/or lid 27. In order to ensure an electrical connection between the EMC protective lining 33a of the box body 26 and the EMC protective lining 33b provided on the lid 27 (particularly in the exemplary embodiment shown in which a sealing element 32 is disposed between the box body 26 and lid 27 which may be electrically insulating), at least one electrically conductive connecting strip 50 may be provided extending between the inner surface of the box body 26 and the inner surface of the lid 27. The connecting strip 50 may be mechanically connected to the box body 26 and lid 27 by appropriate mechanical fasteners 51. The connecting strip may comprise any suitable conductive material within the scope of the invention.

Fig. 6 shows a cross-section through a portion of yet another exemplary battery box 25 of a battery pack of an embodiment of the invention, showing yet another exemplary means of securing the lid 27 to the box body 26. Like features with the battery box shown in Figs. 2 and 4 retain the same reference numerals. In the alternative configuration of Fig. 6, the EMC protective lining 33a on the side wall panels 35 extends across the top edge of the side wall panels 35. The EMC protective lining 33b on the lid 27 extends sufficiently towards the perimeter edge of the lid 27 so that when the lid 27 is placed on the box body 26, the two EMC protective linings 33a, 33b are in contact and so are electrically connected. This contact is also facilitated by the sealing element 32 not being disposed between the box body 26 and lid 27 at the upper edge of the of the side wall panels 35.

The lid 27 includes a closure element in the form of an integral securing skirt 52 depending downwards around the edge of the lid 27. The securing skirt 52 may be a polypropylene component bonded, welded or melted using a heat gun, onto the lid panel 27. Thereby, the closure element, in the exemplary body a securing skirt 52, may be integrally formed with the lid 27. The lid 27 is secured to the box body 26 by mechanical fasteners (not shown) extending through the securing skirt 52 into the side wall panels 35. In the exemplary embodiment shown in Fig. 6, a sealing element 32 is provided between the securing skirt 52 and the box body 26/lid 27 over the join between the box body 26 and lid 27. Although advantageous, the sealing element 32 is not an essential element however.

-13It should be appreciated that the features of the battery boxes 25 shown in Figs. 5 and 6 are interchangeable within the scope of the invention. For example, the angle bracket 49 of Fig. 5 could be omitted and replaced with the securing skirt of Fig. 6, and vice versa. Also, as discussed above, the sealing element 32 maybe omitted. An acceptable level of prevention of dust/contaminant ingress into the battery box 25 may be achieved by the angle bracket 49/securing skirt 52 being secured to the battery box 25, holding the lid 27 securely in place on the box body 26, and covering the join between the box body 26 and lid 27. It will be appreciated that other configurations of securing elements may be provided within the scope of the invention to secure the lid 27 to the box body 26, in addition or alternatives to the angle bracket 49 and securing skirt 52. Also, the angle bracket 49 and/or securing skirt may extend around the entire perimeter of the battery box 25, or may be provided at discrete locations around the perimeter of the battery box 25. Extending around the entire perimeter may advantageously provide enhanced contaminant ingress prevention. Being provided at discrete locations may facilitate ease of manufacture and reduce cost of materials and manufacture.

The high voltage battery pack 14,15 of an embodiment of the invention comprises the exemplary⁷ battery box 25 configuration described above with reference to Fig. 2, and is shown in Fig. 7, again with the lid 27 detached for illustrative purposes, and in crosssection in Fig. 8. A schematic system diagram of the battery pack 15 is shown in Fig. 9. Within the interior of the box 26 is provided a plurality of battery modules 41, which are spaced from each other to define air flow passages 42 between the battery modules 41. Each battery module 41 comprises a plurality of connected cells with appropriate control and balancing electronics (not shown). The battery modules 41 are supported on the floor panel 36, as can be seen more clearly in Fig. 8. The battery modules 41 are positioned on the floor panel 36 such that at least some of the air flow passages 42 between the battery modules 41 align with at least some of the vent holes 38 in the floor panel 36.

Athermal control unit 43 is provided on the side wall panel 35 which includes the inlet and outlet apertures 39, 40. The thermal control unit 43 comprises a housing 44 containing a fan 45 and an air conditioning unit 46. The thermal control unit 43 extends over the inlet and outlet apertures 39,40 and includes an exhaust port 47 aligned with the inlet aperture 39 of the battery box 26 and an intake port 48 aligned with the outlet aperture 40 of the battery box 26. At least one sealing member 53 (see

-14Fig. 8) is advantageously provided between the thermal control unit 43 and the side wall 35 of the battery box 26. A single sealing member 53 may be provided between the thermal control unit 43 and the side wall 35 of the battery box 25. Alternatively, or in addition, a first sealing member 53 may be provided around the exhaust port 47 and the inlet aperture 39 of the battery box 26, and a second sealing member 53 may be provided around the intake port 48 and the outlet aperture 40 of the battery box 26. Therefore, the interior space of the battery box 25 is effectively sealed from the ambient atmosphere. The thermal control unit 43 may be detachably mounted to the side wall panel 35 of the battery box 25, for example by any known releasable attachment elements. This may advantageously enable easy detachment of the thermal control unit 43 from the battery box 25, for example for maintenance or replacement, or to be attached to a different battery pack.

A temperature sensor 54 (see Fig. 9) is advantageously provided within the interior space of the battery box 25 and is connected to a controller 55 to control operation of the air conditioning unit 46 and fan 45. The controller 55 may comprise a vehicle controller for the REEV to which the battery pack 15 is connected. Alternatively, the controller 55 may comprise a separate dedicated battery pack controller. The controller 55 may comprise a processor and a memory, and the memory may have stored various parameters for controlling operation of the thermal control unit. For example, the memory may store upper and lower threshold temperatures for which the thermal control unit may be turned on or off, or at which the thermal control unit may be controlled to heat or cool the interior space of the battery box 26.

The battery pack 15 also comprises a battery management system (BMS) 56 which comprises a controller connected to each battery module 41 and to the controller 55. Referring still to Fig. 9, the battery pack 15 includes positive and negative power output connectors 57,58. The battery modules 41 are electrically connected in series with one battery module 41 at the positive end of the series connected battery modules 41 connected to the positive power output connector 57 via a positive contactor 59. The battery module 41 at the negative end of the series connected battery modules 41 is connected to the negative power output connector 58 via a negative contactor 60. The positive and negative contactors 59, 60 are connected to the BMS 56 and are controllable by the BMS to open and close the connections to the positive and negative power output connectors 57,58 respectively. In an alternative embodiment, the controller 55 may be connected directly to the positive and negative contactors 59, 60

-15to control opening and closing of the connections to the positive and negative power output connectors 57,58 respectively.

In use, the fan 45 causes air to circulate within the battery pack 14,15, to generate a 5 circulating air flow shown by arrows F in Fig. 8. The fan 45 draws air from the interior space of the battery box 25, through the outlet aperture 40, into the thermal control unit 43 and blows the air through the air conditioning unit 46 where the air is cooled or heated as necessary, before continuing through the inlet aperture 39 and into the passage 37 beneath the battery modules 41. The air then flows through the vent holes

38 in the floor panel 36, through the air flow passages 42 between the battery modules and back to the interior space of the battery box 25. As such, the battery modules 41 can be maintained at a desired optimum operating temperature by passing cooling air flow between the modules 41. In colder conditions, the heat generated by the battery modules 41 may be insufficient to maintain the battery modules 41 at the optimum operating temperature, in which case the controller 55, in response to a temperature signal from the temperature sensor 54, would control the air conditioning unit 46 to heat the circulating air flow F to additionally heat the battery modules 41.

Alternatively, in hotter conditions, the heat generated by the battery modules 41 may cause the interior of the battery box 26 to rise to a temperature above the optimum operating temperature of the battery modules 41, in which case the controller 55, in response to a temperature signal from the temperature sensor 54, would control the air conditioning unit 46 to cool the circulating air flow F to cool the battery modules 41.

The battery pack 15 may include additional or alternative temperature sensors connected to the controller 55, as shown in dashed lines in Fig. 9. A first additional temperature sensor 61 may be provided at or within the inlet aperture 39 to measure air temperature flowing into the battery box 26. A second additional temperature sensor 62 may be provided at or within the outlet aperture 40 to measure air temperature flowing out of the battery box 26. The controller 55 may control operation of the fan 45 and the air conditioning unit 46 in dependence upon temperature signals received from one or both of the first and second additional temperature sensors 61, 62. For example, the controller 55 may compare a temperature difference At between a temperature measured at the inlet aperture 39 and a temperature measured at the outlet aperture 40. For example, the controller 55 may control the thermal control unit 43 to operate whilst the outlet temperature remains a predetermined temperature difference above or below a predetermined threshold temperature value or temperature range. In

-ι6addition, or alternatively, the controller 55 may control the thermal control unit 43 to operate if a temperature difference At between a temperature measured at the inlet aperture 39 and a temperature measured at the outlet aperture 40 is greater than a predetermined threshold temperature range, that is a threshold size of At.

Each battery module 41 preferably includes within its own control electronics, its own temperature sensor. As mentioned above, each battery module 41 may advantageously be connected to the BMS 56 which in turn is connected to the controller 55. The controller 55 may therefore control operation of the thermal control unit 43 by comparing the detected temperature from the battery modules 41 with the detected temperature within the battery box 25 from one of the temperature sensors 54, 61, 62 and heating or cooling the circulating air to heat or cool the battery modules 41 as necessary. The thermal control unit 43 may, for example, be controlled such that a difference between the detected temperature from the battery modules 41 and the detected temperature within the battery box 25 from one of the temperature sensors 54, 61, 62 is maintained at or lower than a predetermined temperature difference.

Although the battery pack 14,15 of an exemplary embodiment is described above as comprising a battery box 25 constructed of composite panels 28 comprising a polypropylene core 29 with fibre-reinforced polypropylene skins 31, the invention is not limited to this particular configuration battery box 25. For example, a battery box 25 of a battery pack 14,15 of the invention may alternatively comprise any other suitable material. Other composite panel material may be used, such as a composite panel in which a different plastic or other material may form the core with a plurality of air spaces formed therein. Also the panel skins 31 may be of other configurations within the scope of the invention, such as other plastic, with or without fibre reinforcement. Examples include glass fibre reinforced plastic (GFRP) and carbon fibre reinforced plastic (CFRP) materials. Alternatively, the batteiy box 25 may not comprise a composite panel, and instead may comprise an alternative construction, such as a single-layer or multi-ply material. Other exemplary materials from which the battery box 25 may be constructed include metals, such as steel or aluminium. Such metallic boxes would provide relative ease of manufacture, with steel providing high strength and aluminium a relatively low weight.

In the exemplary embodiment shown, the thermal control unit 43 is disposed on the outside of the battery box 25. However, the invention is not intended to be limited to

-17this configuration and in an alternative embodiment, the thermal control unit 43 may be provided within the interior of the battery box 25. In such an embodiment, a duct may pass from the outlet of the thermal control unit 43 (which would be disposed within the battery box 25), out of the outlet aperture 40 and into the inlet aperture 39 to circulate the air flow F. In a yet further alternative embodiment, the battery box 25 may omit the inlet and outlet apertures 39, 40 and may include an internal passage which directs the air flow F through the passage 37 between the base panel 34 and floor panel 36, though the vent holes 38 in the floor panel 36 and into the remaining interior space of the battery box 25. The thermal control unit 43 may be provided within the passage 37 or may be disposed within the remaining interior space of the battery box

25·

In the exemplary embodiment shown, the battery modules 41 are disposed on a floor panel 36 which is spaced from the base panel 34 to define the air flow passage 37.

However, the invention is not intended to be limited to this configuration and in an alternative embodiment, other support means or support structure maybe provided to space the battery modules 41 from the base panel 34 to define an air flow space beneath the battery modules 41. For example, such a support structure may comprise a mesh or grille mounted parallel to but spaced from the base panel 34. Alternatively, the battery modules 41 may be mounted on individual legs or other supports to raise them up away from the base panel 34.

In the exemplary embodiment shown, a sealing element 32 such as a gasket is advantageously provided between the box body 26 and the lid 27. However, the invention is not intended to be limited to this configuration and in an alternative exemplary embodiment, as described above, a sealing gasket may be omitted.

In the exemplary embodiments illustrated, the EMC shielding is provided as a lining on an inner surface of the battery box 25. However, the invention is not intended to be limited to such configuration, and in an alternative embodiment, an EMC shielding maybe provided as a lining embedded within the composite sandwich panels 28. For example, the EMC lining maybe provided between the core 29 and one of the skins 31. Alternatively, the EMC lining may be embedded within the core 29, or may be formed integrally within one of the skins 31. For example, the skins may be formed of fibreglass fibres and a layer of EMC shielding material, such as woven metallic fibres, embedded in polypropylene. In any such alternative configuration of EMC shielding, it

-18will be appreciated that the EMC shielding material in the box body 26 may be electrically connected to the EMC shielding material in the lid 27. Any such connection means or configuration described above may be used for such electrical connection.

In the schematic system diagram of the battery pack of Fig. 9, positive and negative contactors 59, 60 are shown to open and close the connections to the positive and negative power output connectors 57,58 respectively. These contactors 59, 60 are shown in a simplified schematic form in Fig. 9, although in practice, additional electrical components would be present in the system to regulate current flow within the system as the contactors are operated. Such exemplary contactor electrical arrangements are shown schematically in Figs. 10 and 11, which show parts of the electrical system from points ‘X’ in the system shown in Fig. 1.

High-energy systems such as those which include battery packs 14,15 of the present invention, have large filter capacitors. These are generally in the inverters (not shown) which are part of the high voltage systems to which battery packs 14,15 such as those of the present invention are connected. At the instant of closing the main contactors, these capacitors can cause very large currents to flow unless they are first precharged. This involves charging the capacitors via an appropriately sized resistor. The resistor may limit the current to around 15 - 20A in order that a small capacity precharge contactor can be used.

Two configurations of pre-charge contactor circuit that maybe used are shown in Figs. 10 and 11 respectively, and include a pre-charge resistor 63 in series with a pre-charge contactor 64. The pre-charge resistor 63 is advantageously a positive temperature coefficient resistor, which has the property of resistance increasing as its temperature increases. This has the advantage of providing “in rush” protection - that is, a sudden flow of current though the PTC resistor 63 would cause rapid heating of the resistor 63, and thereby increase of its resistance, in turn preventing or significantly reducing further current flow through the resistor. This acts as a safely device preventing overheating of the circuit components and thereby fire prevention.

In the configuration shown in Fig. 10, the pre-charge resistor 63 and pre-charge contactor 64 are disposed in a parallel circuit 65 across the main positive contactor 59.

In the alternative configuration shown in Fig. 11, the main positive contactor 59 is disposed in a parallel circuit 65 across the pre-charge resistor 63 and pre-charge

-19contactor 64. However, electrically, the configurations of both Figs. 10 and 11 are identical. A voltmeter 66 is provided to monitor the voltage between the positive and negative power output connectors 57,58.

Fig. 12 shows a plot of voltage across the main positive and negative output connectors 57,58 of the system of Fig. 10, against on/off states of the main positive and negative contactors 59, 60 and pre-charge contactor 64 during operation of the system.

Referring to both Figs. 10 and 11, in operation of the battery pack 14,15 and to allow 10 current to flow the following sequence is typically followed:

i) Both the positive and negative contactors 59, 60 and pre-charge contactor 64 initially open;

ii) Close the negative contactor 60;

iii) Close the pre-charge contactor 64;

iv) Monitor voltage at voltmeter 66 after predetermined time (t_pre seconds);

v) Determine if measured voltage is increasing as expected;

vi) Once voltage at or within acceptable range of predetermined voltage level, close positive contactor 59;

vii) Open pre-charge contactor 64.

Referring to Fig. 12, plot ‘A’ represents the voltage across the main positive and negative output connectors 57,58, plot ‘B’ represents the on/off state of the main positive contactor 59, plot ‘C’ represents the on/off state of the pre-charge contactor 64, and plot ‘D’ represents the on/off state of the main negative contactor 60.

Initially at t=o, the process is at step i), in which the positive and negative contactors 59, 60 and pre-charge contactor 64 are open. At ti, the negative contactor 60 is closed, as per step ii). Fig. 12 shows the pre-charge contactor 64 also being closed at ti (step iii), although the pre-charge contactor 64 may be closed a short time after the negative contactor 60 is closed. After elapse of time period t_pre, monitoring of the voltage at voltmeter 66 indicates that the voltage has reached the predetermined level (steps iv) and v)), the positive contactor 59 is closed at t₂ (step vi). Finally, the pre-charge contactor 64 is closed at t₃. Thereafter the battery pack 14,15 is active. If at step v), the system detects that the voltage has not increased within the given time period t_pre, and so the system is not charging as expected, it indicates a system problem and so the main positive contactor 59 is not closed.

- 20 A further alternative configuration of pre-charge contactor circuit is shown in Fig. 13. Here, only a pre-charge resistor 63 is provided in parallel with the main positive contactor 59. There is no separate pre-charge contactor as with the circuits of Figures

10 and 11. A voltmeter 66 is still provided to monitor the voltage between the positive and negative power output connectors 57,58. The process of operating a battery pack having the pre-charge contactor circuit of Fig. 13 would be the same as that described above, except that steps iii) and vii) are omitted and the pre-charging commences as soon as the negative contactor 60 is closed. Upon reaching, or being within an acceptable margin of, the predetermined voltage level, the positive contactor 59 is closed, which closes a parallel circuit around the PTC pre-charge resistor 63 and thereafter, the battery pack 14,15 is active.

The embodiments of the invention shown in the drawings and described above are exemplary⁷ embodiments only and are not intended to limit the scope of the invention, which is defined by the claims hereafter. It is intended that any combination of nonmutually exclusive features described herein are within the scope of the present invention.

Claims

Claims

1. A battery pack for use in an electric vehicle comprising:

a battery box comprising a body portion comprising a base and a plurality of 5 side walls defining an interior space and an upper opening, and a lid secured over the upper opening to close the box portion;

a plurality of battery modules spaced from each other within the body portion; support means supporting the battery modules so as to be spaced from the base panel to define a space between the battery modules and the base panel; and io a thermal control unit configured to circulate air through the battery box through the space between the battery modules and the base panel, and between the battery modules, and to control the temperature of the circulated air.
2. A battery pack according to claim l wherein the support means comprises a 15 floor panel parallel to and spaced from the base panel to define a passage between the floor panel and the base panel, the floor panel including a plurality of apertures extending therethrough to fluidly communicate the passage with the remaining interior space of the box portion.

20
3. A battery pack according to claim 2 wherein the apertures in the floor panel are aligned with the spaces between the individual battery modules.
4. A battery pack according to any of claims l to 3 wherein a side wall of the box portion includes an inlet vent aperture extending therethrough proximate a lower

25 portion thereof and communicating with the space between the support means and the base panel, and an outlet vent aperture extending therethrough proximate an upper portion thereof, and communicating with the remaining interior space of the box portion, wherein the thermal control unit is configured to circulate air out of the box portion through the outlet vent aperture and into the box portion through the inlet vent

30 aperture.
5. A battery pack according to claim 4 wherein the thermal control unit is disposed on the outside of the battery box over the inlet and outlet vents.

35
6. A battery pack according to claim 4 or claim 5 wherein the area of the outlet vent aperture is substantially the same as the area of the inlet vent aperture.

- 22
7- A battery pack according to any of claims 5 or claim 6 wherein the thermal control unit is detachably mounted to the outside of the battery box by releasable fastening elements.
8. A battery pack according to any preceding claim wherein at least one of the base wall, side walls and lid comprise a composite panel comprising a core having a plurality of cavities therein and first and second skins respectively bonded to first and second opposite sides of the core.
9. A battery pack according to claim 8 wherein all of the base, side walls and lid comprise the composite panels.
10. A battery pack according to claim 8 or claim 9 wherein the core comprises a 15 honeycomb structure.
11. A battery pack according to claim 10 wherein the honeycomb core is made of polypropylene and the skins comprise glass fibre reinforced polypropylene sheets.

20
12. A battery pack according to any preceding claim wherein at least two out of the base and side walls are integrally formed from a single composite panel.
13. A battery pack according to any preceding claim wherein the side wall panels, base panel and lid include an EMC shielding.
14. A battery pack according to claim 12 or claim 13 wherein the EMC shielding lining comprises a woven fabric of metallic fibres.
15. A battery box according to claim 13 or claim 14 wherein the EMC shielding

30 comprises a lining on the inside surfaces of the side wall panels, base panel and lid.
16. A battery box according to claim 13 or claim 14 wherein the EMC shielding comprises a layer of material embedded within at least one of the side wall panels, base panel and lid.

-2317- A battery pack according to any preceding claim wherein an airtight seal is formed at the junction where each side panel, base panel and the lid abut.
18. A battery pack according to any preceding claim further comprising a first

5 temperature sensor disposed within the box portion, and a controller connected to the first temperature sensor and thermal control unit and configured to control operation of the thermal control unit in dependence on a signal received from the first temperature sensor.

io
19. A battery pack according to claim 18 wherein the controller is configured to control the thermal control unit to cool the circulated air if the sensed temperature is above a first pre-determined threshold temperature, and is configured to control the thermal control unit to heat the circulated air if the sensed temperature is below a second pre-determined threshold temperature.
20. A battery pack according to claim 18 or claim 19 further comprising a second temperature sensor connected to the controller, and wherein the controller is configured to control operation of the thermal control unit in dependence on signals received from one or both of the first and second temperature sensors.
21. A battery pack according to claim 20 when dependent on claim 4, wherein the first temperature sensor is positioned proximate the inlet vent aperture to measure the temperature of air flowing into the battery box, and the second temperature sensor is position proximate the outlet vent aperture to measure the temperature of air flowing

25 out of the battery box.
22. A battery pack according to claim 20 or claim 21 wherein the controller is configured to determine a temperature difference between a temperature measured by the first and second temperature sensors and to control the thermal control unit in

30 dependence on the determined temperature difference.
23. A battery pack according to claim 22, wherein the controller is configured to control the thermal control unit to operate whilst the difference between temperatures sensed by the first and second temperature sensors exceeds a predetermined threshold

35 temperature difference.

-2424- A battery pack according to any of claims 20 to 23 when dependent on claim 21, further comprising a third temperature sensor disposed within the battery box and spaced from the inlet and outlet vent apertures, and wherein the controller is configured to control the thermal control unit in dependence upon signals received

5 from the first, second and third temperature sensors.
25. A battery pack according to any of claims 18 to 24 wherein each battery module comprises a respective module temperature sensor, and the controller is configured to control operation of the thermal control unit in dependence signals received from the

10 first temperature sensor and the module temperature sensors.
26. A battery pack according to any of claims 18 to 25 wherein the controller comprises a first controller, and the battery pack further comprises a second controller connected to each battery module, and wherein the first controller is configured to

15 control operation of the thermal control unit in dependence on signals received from the second controller.
27. A battery pack according to claim 26 when dependent on claim 25, wherein the second controller is configured to determine the temperature of each battery module

20 and to determine a range of module temperatures, and the first controller is configured to operate the thermal control unit when the range of module temperatures exceeds a predetermined temperature difference.
28. A battery pack according to any of claims 18 to 27 comprising positive and

25 negative power output connectors, and respective positive and negative contactors to control the connection between the battery modules and the respective positive and negative power output connectors, wherein the first or the second controller is connected to the positive and negative contactors and is configured to control operation of the positive and negative contactors.
29. A method of controlling the temperature within a battery pack for use in an electric vehicle comprising a battery box comprising a body portion comprising a base and a plurality of side walls defining an interior space and an upper opening, and a lid secured over the upper opening to close the box portion, a plurality of battery modules

35 spaced from each other within the body portion, and support means supporting the battery modules so as to be spaced from the base panel to define a space between the

-25battery modules and the base panel, and a thermal control unit, the method comprising operating the thermal control unit to circulate air through the battery box through the space between the battery modules and the base panel, and between the battery modules, and controlling the temperature of the circulated air.
30. A method according to claim 29 wherein the support means comprises a floor panel parallel to and spaced from the base panel to define a passage between the floor panel and the base panel, the floor panel including a plurality of apertures extending therethrough to fluidly communicate the passage with the remaining interior space of

10 the box portion, the method comprising circulating the air through the passage the through the apertures in the floor panel.
31. A method according to claim 29 or claim 30 comprising circulating the air into the box portion through an inlet vent aperture extending through a side wall of the box

15 portion proximate a lower portion thereof and communicating with the space between the support means and the base panel, and out of the box portion through an outlet vent aperture extending through a side wall of the box portion proximate an upper portion thereof and communicating with the remaining interior space of the box portion.
32. A method according to claim 31 comprising disposing the thermal control unit on the outside of the battery box over the inlet and outlet vents.
33. A method according to any of claims 29 to 32 comprising providing a seal

25 between the box portion and the lid to form an air-tight seal between the box portion and the lid.
34. A method according to any of claims 29 to 33 comprising providing at least one of the base wall, side walls and lid from a composite panel comprising a core having a

30 plurality of cavities therein and first and second skins respectively bonded to first and second opposite sides of the core.
35. A method according to claim 34 comprising providing all of the base, side walls and lid as the composite panels.

- 26
36. A method according to any of claims 29 to 35 comprising detecting a temperature within the box portion using a first temperature sensor disposed within the box portion, and controlling operation of the thermal control unit using a controller connected to the first temperature sensor and the thermal control unit, in dependence

5 on a signal received from the first temperature sensor.
37. A method according to claim 36 wherein the battery pack further comprises a second temperature sensor connected to the controller, and wherein the method comprises controlling operation of the thermal control unit in dependence on signals

10 received from one or both of the first and second temperature sensors.
38. A method according to claim 37 when dependent on claim 31, comprising measuring the temperature of air flowing into the battery box by the first temperature sensor positioned proximate the inlet vent aperture, and measuring the temperature of

15 air flowing out of the battery box by the second temperature sensor positioned proximate the outlet vent aperture.

29. A method according to claim 37 or claim 38 comprising determining a temperature difference between a temperature measured by the first and second

20 temperature sensors and controlling the thermal control unit in dependence on the determined temperature difference.
40. A method according to claim 39, comprising controlling the thermal control unit to operate whilst the difference between temperatures sensed by the first and

25 second temperature sensors exceeds a predetermined threshold temperature difference.
41. A method according to any of claims 37 to 40 when dependent on claim 38, wherein the battery pack further comprises a third temperature sensor disposed within

30 the battery box and spaced from the inlet and outlet vent apertures, and wherein the method comprises controlling the thermal control unit in dependence upon signals received from the first, second and third temperature sensors.
42. A method according to any of claims 29 to 41 wherein each battery module

35 comprises a respective module temperature sensor, and method comprises controlling

-τηoperation of the thermal control unit in dependence signals received from the first temperature sensor and the module temperature sensors.
43. A method according to any of claims 29 to 42 wherein the controller comprises

5 a first controller, and the battery pack further comprises a second controller connected to each battery module, and wherein the method comprises the first controller controlling operation of the thermal control unit in dependence on signals received from the second controller.

10
44. A method according to claim 43, comprising the second controller determining the temperature of each battery module and determining a range of module temperatures, and the first controller operating the thermal control unit when the range of module temperatures exceeds a predetermined temperature difference.

15
45· A method according to any of claims 29 to 44 wherein the battery pack comprises positive and negative power output connectors, and respective positive and negative contactors to control the connection between the battery modules and the respective positive and negative power output connectors, wherein the method comprises the first or the second controller being connected to the positive and

20 negative contactors and controlling operation of the positive and negative contactors.
46. A battery box substantially as herein described with reference to the accompanying drawings.

25 47. A method of controlling the temperature within a battery pack substantially as herein described with reference to the accompanying drawings.

Intellectual

Property

Office

Application No: GB1615195.3 Examiner: Mr Gareth John