AU2021102710A4

AU2021102710A4 - Battery assembly and casing therefore

Info

Publication number: AU2021102710A4
Application number: AU2021102710A
Authority: AU
Inventors: Brent Singer
Original assignee: Bluelithium Pty Ltd
Current assignee: Bluelithium Pty Ltd
Priority date: 2021-05-20
Filing date: 2021-05-20
Publication date: 2021-08-05
Anticipated expiration: 2029-05-20

Abstract

A lithium-ion battery pack is disclosed. The battery pack comprises a plurality of lithium-ion cells within a housing. The he housing comprises a metallic elongate member; having a constant cross section that is circular, oval, obround or a rounded polygon, or any other shape 5 that does not have a defined corner; a base end; a top end; a top waterproof sealing member and a bottom waterproof sealing member. The battery pack finds application in marine environments. Figure 1 1/7 -T cD

Description

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BATTERY ASSEMBLY AND CASING THEREFORE FIELD

The present disclosure relates to a battery assembly and casing therefore. The disclosed battery assembly and casing has particular application in marine environments.

BACKGROUND

The reference to background art in this specification is not intended to, and should not be taken as, an acknowledgment, statement, suggestion or admission that the referenced prior art forms part of the common general knowledge in Australia or in any other country.

Over recent years, lithium ion batteries have replaced lead-acid batteries for rechargeable .0 energy storage applications in off-grid systems. Lithium ion batteries have high energy density and high efficiency. This enables lithium batteries to have a more compact size and weight than lead acid batteries, for example they can reduce the weight of a battery bank by half. Other advantages include that Lithium ion batteries can be discharged to between 10 to 20% capacity, charges up to five times faster than a compared to conventional lead-acid batteries .5 and can hold their charge for extended periods of time.

Lithium ion storage batteries have many energy storage applications and are used in many different environments. Batteries, especially high-power batteries, of 12V, 24V, 48V are potentially dangerous, especially around water. Water of course is a strong conductor and has the potential to damage the inbuilt safety functions of the battery. This may lead to fires, .0 loss of an expensive battery to damage, burnt wires and possible electrocution by contact with a damaged battery. Batteries may also be damaged by impact or puncture of the battery casing.

For the above reasons, high energy battery storage on boats has been limited to arrays stored in air-conditioned watertight racks. This is inefficient use of space and incurs additional cost.

The present disclosure is addressed towards providing a battery housing or applications where battery energy storage systems are exposed to a marine environment, or potentially exposed to water or other liquid and/or mechanical damage, and that may be more cost effective than conventional battery systems.

DEFINITION

In the specification the term "comprising" shall be understood to have a broad meaning similar to the term "including" and will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. This definition also applies to variations on the term "comprising" such as "comprise" and "comprises".

SUMMARY

In one aspect there is disclosed a lithium-ion battery pack comprising a plurality of lithium-ion cells within a housing, wherein the housing comprises a metallic elongate member; having a .0 constant cross section that is circular, oval, obround or a rounded polygon, or any other shape that does not have a defined corner; a base end; a top end; a top waterproof sealing member and a bottom waterproof sealing member.

Lithium-cells cylindrical, or prismatic, cylindrical preferred.

The term rounded polygon refers to a polygon having rounded corners. Rounded corners .5 have a corner radius, being the radius of the circle created if the curve was extended to create a full circle.

In one aspect, the polygon is a rounded pentagon, hexagon, heptagon or octagon.

The corner radius of the polygon may be the same or different. Where the cell is a cylindrical cell, the corner radius may be substantially the same as the cell radius so as to allow more .0 efficient packing of the cells within the casing.

The elongate configuration and rounded shape of the housing makes a substantial contribution to the working of the invention in a number of ways. A rounded shape is stronger that shapes with sharp corners as impact and stress is transferred around round walls rather than concentrated at the corner features. The round shape allows for the use of cost effective and efficient seals such as 0 rings and gaskets. Even further, a rounded shape may deflect a blow rather than absorb the blow and may be more resistant to puncture damage. The elongate rounded shape also allows for more ergonomic handling.

The metallic material is suitably aluminium and may be coated for corrosion resistance.

The thickness of the metallic material is suitably sufficiently thick to impart a degree of impact resistance.

The type, number and configuration of the lithium-ion cells is not limited and may be selected and designed by those skilled in the art according to common general knowledge. The battery pack may supply power at 12V, 24V, 48V, 96V and higher.

Lithium-ion cells used in power storage may range between 3.2V and 3.7V and between 1AH to 8AH. 12, 14, or 16x 3.7V cells may be connected in series to provide 48V.

The lithium cells may be arranged in any suitable configuration depending upon the desired power supply and the cell specifications.

In one aspect, as the housing is elongate, the lithium-ion cells may be arranged in two or more clusters or modules, each having a specific number of cells mounted on top of the other.

.0 In an exemplary aspect, the battery pack may comprise between three and nine modules, preferably seven or eight modules.

In another aspect, with more powerful cells, there may be one or more layer of a single large cell.

The battery pack may be configured such that if one cluster or module fails, it may be isolated .5 and replaced.

Alternatively, the whole battery pack may be simply replaced with a new unit at the operating location and the failed pack is returned for repair. This is known in the maintenance arts as a line replaceable unit (LRU).

The advantageous ergonomics of the elongate rounded shape facilitates the replaceability of the packs.

An exemplary battery pack may have a voltage range from about 40V to about 100V; about 20AH to about 60AH; and deliver power from between about 0.8kWH to about 3.6kWH.

Two or more battery packs may be combined, either serially or in parallel to provide a battery bank having a desired power output for a particular application or power.

The battery pack comprises a top sealing member and a base sealing member for waterproof sealing of the housing.

The sealing members suitably comprise one or more 0 rings or a gasket. The rounded shape of the housing has a still further advantage in that it facilitates sealing using these cost effective methods. The sealing members are suitably configured for insertion into the respective ends of the housing. However, the sealing members may also be in the form of an o ring sealing flange as is known in the sealing arts.

In one aspect, the top sealing member may have the battery management system (BMS) mounted or installed thereto or therein.

In another aspect, the BMS may be mounted or installed in the base sealing member.

The battery pack may be fabricated by connecting the lithium-ion cells to form a cell subassembly and then inserting the cell subassembly into the housing.

Also disclosed is a lithium-ion cell subassembly comprising a plurality of cylindrical lithium-ion cells, comprising at least two lithium-ion cell modules mounted on top of the other.

.0 In one aspect, each module includes protective features, such as thermal or electronic fuses, thermal or other sensors, and may affect isolation of the connected module in response to malfunction of a lithium-ion cell in that module.

In another aspect, the substrate is a circuit board for electrical connection of the cells. This may limit or avoid the use of electrical connecting cables. Cables are flexible and are the .5 cause of many failure modes in conventional battery systems. Cables are also flammable.

In one aspect, the circuit boards are constructed from an inflammable material that may serve as a "fire break" between modules.

The circuit board may be configured to mechanically support and retain the cells in a predetermined manner. In one aspect, the circuit board is configured to retain the cells a predetermined distance apart so as prevent heat transfer, therein halting propagation of thermal faults to neighbour cells.

The circuit board may also be provided with fuses, temperature sensors or other cell monitoring features. These my monitor humidity, still or flowing water, galvanic isolation, volatile organics (smoke), or pressure.

In a preferred aspect the battery pack comprises an elongate circuit card to which each module is connected and that connects to the BMS.

The circuit card may also provide a second layer of cell monitoring that is independent of the BMS so as to provide an additional level of safety. For example, the elongate circuit card may comprise independent temperature sensors.

Use of the circuit card still further avoids the use of cables or connectors. It is preferred that the modules are connected to the circuit card by non-removable methods for example by soldering.

The Detailed Description makes reference to the accompanying drawings, by way of example. These drawings are provided to assist an addressee in understanding the applicant's invention how it is implemented, and the working advantages conferred by the invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a perspective view of a battery pack according to one aspect of the invention;

Figure 2 is a cut away of the battery pack as shown in Figure 1;

.0 Figure 3 is a perspective view of the interior cell sub-assembly of the battery pack as shown in Figure 1;

Figure 4 is another view of the interior subassembly of Figure 3 with the BMS connected thereto;

Figure 5 is a schematic view of an alternative interior cell sub-assembly as disclosed herein;

.5 Figure 6 is an end view of the casing prior to assembly of the battery pack; and

Figure 7 is a view showing insertion of the interior cell subassembly into the casing.

DETAILED DESCRIPTION

Figure 1 shows a battery pack 10 according to one aspect of the disclosure. The battery pack 10 has a cylindrical casing 12. The casing is about 600mm to about 800mm in length with a diameter of about 100mm to about 200mm. The casing 12 is formed from extruded 2.5mm aluminium tube with a corrosion resistant coating.

The 2.5mm aluminium is puncture resistant. Further the cylindrical shape is more structurally sound, self-supporting and stronger than square or rectangular shapes. Still further if struck by a sharp object, a rounded shape will tend to deflect a blow. Even further, the rounded geometry vastly improves sealing against water, either flowing or still. This vastly improves protection of the cells from damage due to jest of water or solvent in cleaning.

Further, a rounded tube shape spreads internal stress caused by a pressure build up. This will be discussed further below.

All of the above advantages of a rounded shape may be achieved with a cut to length extrusion. This makes the casing very cost efficient when compared to fabrication of conventional rectangular casings.

The casing 12 has a top end 14 and a base end 16. One or both ends 14, 16 may have a carry handle 18. Two handles allow the battery pack 10 to be easily carried by two people by holding a handle at each end. Alternatively, the battery pack may be lifted and carried by a single person. The elongate shape of the battery pack 10 makes lifting much easier as it is a straight up lift and does not require bending over, and therefore a safer lift. This avoids a 'cantilever' in lifting, which requires serious effort and stress on the body.

.0 This may be compared to lifting a conventional rectangular shaped battery that requires a user to bend over.

The elongate shape also facilitates handling when hauling into and out of a boat or any other awkward or confined space. This requires manoeuvring up and down stairs, small entries, hatches and the like.

.5 The top end 14 and the base end 16 each have a sealing member 20, 22. The sealing members 20, 22 provide a watertight seal. The seal is created by a conventional 0 ring or gasket seal. The advantage of such sealing members is that they are cost effective, easy to install and may provide excellent water resistance. This may be compared to methods of sealing rectangular shaped battery packs, such as by providing thermoplastic rectangular .0 casings that are solvent welded to a thermoplastic cover.

An advantage of the present seals is that they may be easily removed for servicing and/or replacement of cells.

Still further, as mentioned above the round shape spreads pressure. A pressure increase within the casing may occur such as an exploding lithium-ion cell. The top end sealing member and base sealing members 20, 22 are configured to be sacrificial in the event of pressure reaching a predetermined level. In this case, the top end and/or base sealing member 20, 22 will fail and safely vent the pressure. It will be appreciated that an exploding aluminium tube would be very dangerous.

The top end sealing member 20 has a battery management system (BMS) installed therein. The BMS regulates, monitors and controls charging, discharging of rechargeable lithium batteries and loss of isolation detection. The BMS will generally monitor battery cell temperature, short circuit protection, under and over charge protection, damaged cell isolation, short circuit protection, cell balancing, leak detection and earth fault detection. The BMS incorporates a traction switch to isolate the battery on command or fault; which may be an e switch, or electromechanical contactor, or both.

The top sealing member 20 is spaced from the top end 14 of the tubular casing 12 to protect the BMS.

The battery pack 10 also has a hydrophobic air vent (not shown) that allows for pressure equalisation without allowing ingress of water or other liquid or moisture. The pressure equalisation protects the 0 ring and gasket seals from pressure induced mechanical movement cycles. Without such pressure equalisation, the temperature induced pressure .0 changes associated with service/idle or day/night thermal cycles cause the 0 rings to 'breathe' and suck in dirt, moisture, oil, grease, and other debris. This may cause a failure mode, and/or reduce the effective life of the seal.

In one aspect, two seals maybe used. The first is a sacrificial 'weather seal' the second is a high reliability pressure seal.

.5 Figure 2 shows a cutaway of the battery pack 10 to show the arrangement of the cells 30 therein.

Figures 3 and show an internal cell subassembly 32. The cells 30 are 3.7V lithium iron phosphate (LIFEPO4 ) that are not susceptible to ignition.

In the sub assembly 32 of Figure 3, there are seven clusters 34 of cells 30.

.0 Each layer 34 of cells 30 is mounted on a substrate 36 that is circuit board, often called an interposer card. The substrate a) mechanically orients and support the cells enforcing the 2mm cell gapping of about, 2mm, b) has fuses to protect the cells in handling and manufacture, as well as during operation in the field, c) it is made from high temperature materials (such as FR4 self-extinguishing fibreglass) so as to provide a firebreak, and d) has features to allow the attachment to an internal connection that is an elongate circuit card or "spine" 38 for connecting the main BMS.

The spine 38 is a circuit card, made from high temp materials and is inflammable. The spine 38 replaces any cables in the system. Its use is in voltage sensing and 'cell balancing' and also it mounts temperature sensors that monitor cells that are remote from the BMS itself.

The system is configured to minimise connectors, wiring and the like that may be a source of flammable materials and potential sources of failure or fault. Thus, the interposers for each module are soldered to the spine such that the attachment is permanent. The spine 38 also includes temperature sensors for select cells.

As a still further safety precaution the BMS is monitored by a supervisor processor that performs CBIT (continuous built in testing) of the system to detect malfunction and can take safety and remedial actions when problems occur. These are not exclusively detection of problems, warning of operators, and self-protection actions. Each BMS contains optical, and audible warnings as local user interface, as well as network communication to propagate warnings to appropriate supervisory systems.

Figure 4 shows the full cellpack and BMS subassembly 40. The spine 38 is soldered to each .0 interposer 36 but has a connector 38 at the BMS attachment. This is a high reliability method, to minimise the number of connectors. Connectors are points of failure. Spine attachment is permanent, but the BMS can be removed for service, recycled or replacement.

The configuration and type of the cells 32 may be selected according to the desired Voltage and power of the battery pack as is well known in the battery art.

.5 In one configuration, the battery pack has a voltage range of about 58.4V to 40V and sustained 40A @51.2V nominal that can deliver 2.33KWH. For example, six to ten battery packs may be required to drive a 10KW yacht motor.

The lithium ion cell configuration may therefore comprise 3.7V 6A cells in a 14S 6A configuration. Each of the seven clusters has 16 cells. The cells have heatsinking and .0 corrosion sealing at both ends and are air gapped at 2mm apart as a thermal break against cell to cell heating. The aluminium casing has a high thermal transfer.

Another exemplary configuration is shown in Figure 5. In this configuration the sub assembly 50 has are eight layers of 16 3.2V 6Ah cells 30, 16S8) 48Ah (i.e. 16 cells in series and 8 in parallel).

Each layer of cells 30 is mounted on a substrate 36 that is circuit board interposer card 52. The substrate a) mechanically orients and support the cells enforcing the 2mm cell.

The cells are 'doubled back' around so start and finish of the serial 'stack' is the BMS 40. Figure 5 also shows a base shock gasket 54 and a mat 56.

Figure 6 shows the raw aluminium tube 12 prior to fabrication of the battery pack. The aluminum tube 12 has been cut to size and drilled for handle holes 38. The edges are deburred and smoothed to aid assembly and cleaned for particulate, oil, and ionic/salty contaminants.

The base sealing member is then installed into one end of the casing. The base sealing member is a round sealing ring with 0 rings.

The cell subassembly is then inserted into the casing as shown in Figure 7 and the top sealing member and BMS is then installed into the casing.

As discussed above, the sealing members have a weaker construction than the aluminum casings. This is intentional in case of overpressure this will yield and fail and direct the released pressure in a predetermined direction, thus providing an even further safety feature.

.0 It will be appreciated that the disclosed battery pack has several practical advantages. The housing has no sharp corners and is therefore easier to handle, is more puncture resistant, more accidental damage resistant than conventional rectangular batteries.

The battery packs are waterproof that allows their use in areas that may otherwise not have been available for battery storage. Examples include bilge, crawlspaces, or areas that are .5 open to salt air and spray. Marine use is of course not limited to sailing yachts, but any suitable marine vessel including power cruiser, house boats, water taxis, vessels that may be used in poor weather or dangerous conditions such as search and rescue vessels, trawlers. The disclosed battery packs may also be used in any other marine environment such as mariners, docks, off grid holiday accommodation, marine research facilities and off road 4WD use.

.0 The battery packs may be scaled up for traction and domestic loads.

It will be appreciated that various changes and modifications may be made to the invention as described and claimed herein without departing from the spirt and scope thereof.

Claims

1. A lithium-ion battery pack comprising a plurality of lithium-ion cells within a housing, wherein the housing comprises a metallic elongate member; having a constant cross section that is circular, oval, obround or a rounded polygon, or any other shape that does not have a defined corner; a base end; a top end; a top waterproof sealing member and a bottom waterproof sealing member.

2. The battery pack of claim 1, wherein the polygon is a rounded pentagon, hexagon, heptagon, or octagon. .0

3. The battery pack of claim 2, wherein the cell is a cylindrical cell with a radius and the corner radius pf the rounded polygon may be substantially the same as the cell radius.

4. The battery pack of any one of claims 1 to 3, wherein the metallic material is aluminium .5 and coated for corrosion resistance.

5. The battery pack of any one of claims 1 to 4, wherein the lithium-ion cells are arranged in two or more modules, each having a specific number of cells, the modules being mounted on top of the other. .0

6. The battery pack of claim 5, further comprising an elongate circuit card extending along a length of the casing to which each module is electrically connected.

7. The battery pack of any one of claims 1 to 6, wherein the battery pack has a voltage range from between about 40V to about 144V; and AH value of between about 20AH to about 120AH.

8. The battery pack of any one of claims 1 to 7, wherein each of the top sealing member and base sealing member comprise one or more 0 rings or a gasket and configured for insertion into the respective ends of the elongate member.

9. The battery pack of any one of claims 1 to 8, wherein the top sealing member has battery management system (BMS) mounted to or installed therein.

10. A lithium-ion cell subassembly comprising a plurality of cylindrical lithium-ion cells, comprising at least two lithium-ion cell modules mounted on top of the other, each module comprising at least two lithium-ion cells.

11. A self-storage energy system comprising two or more battery packs of any one of claims 1 to 9.

12. A method of fabricating a battery pack of any one of claims 1 to 9, comprising providing a lithium ion subassembly of claim 10, providing an elongate metallic member, installing the subassembly into the elongate metallic member.