Conformable Battery Packs
FIELD OF THE INVENTION
This invention relates to thin electrical -power source packs that are body-mountable for human wearers .
BACKGROUND OF THE INVENTION
The standard power source for a portable application is a rechargeable battery pack. This is a metallic or plastic box, containing cells connected in series and/or parallel. Typically this box is rectangular and can only be mounted in certain positions on the body e.g. on the belt. This can often be inconvenient to the user, in activities like running and crawling. The weight of the metal or plastic also reduces the energy density of the power source .
Lithium ion cells have the highest energy density of currently available rechargeable batteries. Initially, the cells were cylindrical. Subsequently, rectangular or prismatic cells in metal cans were produced, followed by soft pack cells in an aluminium laminate bag material. Applications like mobile phones demand a thin battery, and they can also be useful in devices like laptop computers .
SUMMARY OF THE INVENTION
This invention overcomes the inconvenience of the standard power sources by providing a pack that is relatively thin and that is sufficiently flexible to be body-conformable when worn and/or adaptable to conform to the contours of a non-planar worn object such as a rigid helmet or substantially inflexible body armour. Thus, with a flexible body-conformable pack of the invention, as the body contours alter with movement, so the power- source pack will move and conform to whatever shape the body takes up.
Thus, in one aspect the invention provides a thin body-mountable electrical-power source pack for a human wearer that is sufficiently flexible to be body- conformable and contains one or more flat rigid lithium, metal/air or fuel cells or any combination of two or more thereof .
In another aspect of the invention there is provided a thin body-mountable electrical-power source pack for a human wearer that is sufficiently flexible to be conformable to the contours of a rigid worn object, and contains one or more flat rigid lithium, metal/air or fuel cells or any combination of two or more thereof.
The pack may be in the form of an item or part of an item of clothing carrying the cell(s) and may, for example, be worn in the small of the back, between layers of clothing, on a helmet, on body armour, or in a pocket on the thigh.
Also, the pack may be in the form of webbing carrying the cell(s) .
The pack may be rigid. Preferably, the pack is sufficiently flexible for it to be capable of conforming to the contours of the part of the human body, or of a fixed or rigid object, such as a helmet or body armour worn by a human being, where it is to be mounted. Thus, the term "body-conformable" as applied to the pack means that the pack is capable of conforming to the contours of a rigid object that is worn on the human body, and/or is capable of conforming to the contours of part of the human body when in use. Suitable fabric materials are appropriate for this purpose, subject to their having sufficient durability for the wearer's needs. Where the pack is to be mounted on a rigid object such as a helmet suitable adhering means may be employed comprising fabric connectors, such as webbing, VeIcro and the like.
By "thin" is meant that the maximum thickness of the pack is of the order of or not significantly greater than the thickness of clothing and/or webbing normally worn by military personnel. For example, the maximum thickness of the pack is no greater than 40 mm, such as no greater than 30 mm.
For the pack to be "thin", the cell(s) themselves must be thinner than the pack. The cells may be from 2 to 20 mm thick, more preferably from 4 to 16 mm thick, more preferably 6 to 10 mm thick. In a particularly preferred embodiment the cells are 10 mm thick. For example, cell(s) of thickness 18 - 20 mm such as are known in the art may be used.
The cell(s) themselves are rigid or substantially inflexible. A pack including a plurality of rigid cells can be configured in a co-planar arrangement to have sufficient flexibility to be body-conformable. For example, the pack can bend along the gaps or axes between the cells. Depending on the thickness of the cells it may be possible to bend the cells slightly without breakage, and without deleterious effect on the power generating capacity of the cells. However, a rigid cell will typically break if it undergoes an extreme amount of bending, for example if it is folded in half.
The cell(s) may be primary or secondary. As examples of electrochemical cell(s) that may be used in the invention, there may be mentioned lithium cells such as rechargeable lithium cells, lithium ion cells, lithium ion polymer cells, lithium metal cells, lithium metal polymer cells and lithium primary cells, metal/air cells and fuel cells. A thin, planar geometry can be advantageous for cells with air electrodes, to give a relatively large area for air ingress.
The cells may be connected in series or parallel in the pack . In one embodiment the pack may contain two or more groups of cells where the cells in each group are connected in series and the groups of cells are connected in parallel.
The pack may contain one or more layers of cells. Depending on the capacity of the cells and the number of layers of cells in the pack, it is possible to assemble packs of the same size but with different stored energies .
The pack of the invention may contain two or more different types of cell, such as selected from rechargeable cells, fuel cells and super capacitors.
Where lithium ion or other cells that can form a smart battery are used then the power pack preferably forms a smart battery. In a particularly preferred embodiment the smart battery also incorporates a battery health indicator which gives an indication of the maximum charge capacity as a proportion of the original charge capacity. In a preferred embodiment the power pack is compatible with a smart charger capable of level 3 charging. A smart battery is a battery which complies with the Smart Battery Data Specification revision 1.1. A smart charger is' a charger which complies with Smart Battery Charger Specification revision 1.1.
In a preferred embodiment each cell is protected against short circuits . Where the cell is a lithium ion cell it is preferably protected against over-charging and against short circuit by an internal safety device, or for example by using a K2 cap cell protection device similar to that used in Li-ion D cells available from AGM Batteries Ltd. In one embodiment there is also a further cell protection circuit for the power pack as a whole.
The cells in each power pack are separate entities from one another.
Advantageously, the pack of the invention contains, within the pack an EMC interference abatement layer. Typically all the cells are encased in a single EMC interference abatement layer such as a metal mesh. However, each cell or electronic circuit board can be encased by a separate mesh enclosure. The EMC abatement layer is connected to a common ground typically through the connector that attaches to the equipment to be powered. Where the equipment is used in a stationary manner the equipment may have an earth connection. In one embodiment the cells are encased in foam and the EMC abatement layer is a single layer round all the cells, typically just inside an outer waterproof layer.
The cells are typically encased in foam. In a preferred embodiment the foam is a flame retardant foam. The foam on each side of the cells may be the same thickness or different thicknesses. In a preferred' embodiment thicker foam is used on the side that is against the body in operation. The foam is typically from 2 to 20 mm thick, preferably 4 to 15 mm thick, most preferably 10 mm thick.
In a preferred embodiment all the cells are encased in a waterproof cover. Thus, although the power pack as a whole may get wet, no water will contact the cells. This waterproof cover also keeps the foam dry.
Optionally and desirably, an indicator to display, directly or indirectly, information concerning the state of charge of the power source may be included. Such indicators may be referred to as "fuel gauges" . Such information may, for example, be relayed through a connector to be displayed visually upon activation by means of a switch or button. Alternatively, the information may be conveyed to host equipment such as a laptop computer or mobile telephone to enable it to be accessed by the user.
In a further embodiment, the power source may include an indicator to display information concerning the state of health of a rechargeable battery or cell. Thus the indicator may display the maximum charge capacity of the battery as a proportion of the original maximum charge capacity. In a preferred embodiment the outer covering of the power pack has connectors attached to it which enable the pack to be mechanically connected to a harness, rucksack or other equipment . Typically the connectors are the universal clips as found on many rucksacks.
Alternatively, zips may be used to secure the power pack.
It is an object of the present invention to provide a power pack for powering equipment such as radios, portable computers or powered tools.
DETAILED DESCRIPTION OF THE INVENTION
EXAMPLE
The invention will now be particularly described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a schematic plan view of a power- source pack in the form of a pouch, displaying electrochemical cells, and
Figure 2 is- a schematic side view corresponding to Figure 1.
Referring to Figure 1, four thin planar electrochemical cells 1, 2, 3 and 4 are mounted on and in foam padding 5 which is contained within a protective flexible outer layer 6. Also provided within the foam padding 5 is an electrical connector 7.
Fold lines 9 are shown about which the power-source pack can be flexed to enable it to be inserted into the clothing of a user and conform to the contours of the body of a user.
Referring to Figure 2, two of the planar cells 1 and 2 are shown mounted in the foam padding 5. The protective outer layer 6 and the electrical connector 7 are also shown.
Both Figures 1 and 2 show an EMC interference abatement layer 8 as dashed lines.
The protective outer layer 6 may, if necessary, be made of waterproof material which is preferably a breathable material such as Gortex ™.