If a battery is indispensible in your vehicle, why not make its contribution structural as well as electrical?
A unique concept in energy storage using interlocking structural cells to contain a battery's chemicals could soon revolutionise design of road and racing vehicles. TWI's recent involvement in the design of batteries which also contribute structurally to the vehicle’s chassis has been reviewed in hybrid vehicle designs. Now it looks likely to be taken up by commercial and competition vehicles.
The cells themselves could be plastics-based with a co-extruded conductive coating, or metal-based using aluminium. ‘TWI’s role involves examining all the joining aspects relating to the Battrix concept, as it’s known’ explains TWI’s Paul Burling. ‘A battery requires chemicals, for example lead acid, lithium polymer or lithium iron in liquid or gel form. What we’re doing is taking those chemicals and incorporating them, not in a battery cell as a separate entity, but within the structural elements of the vehicle, such as the floor or loading bay.’
A separate but related issue that has to be addressed is joining the individual cells together. These cells have to be tack welded or joined using some form of mechanical fastening. When assembling the cells, welding can cause serious harm to the battery chemistry because of localised heating, reducing their performance.
So the Battrix concept was designed to increase the surface area of the anode and the cathode and provide a structural mechanical interlocking cell. Having a large interlocking surface area on the anode and cathode allows greater power (volts and amps) to be drawn out of the battery, without causing high electrical resistance therefore reducing heating.
As an example if you use aluminium sandwich structures to make a large floor pan for say a convertible car, then one way of doing it, instead of actually bonding the honeycomb to the aluminium sheets, is to stake weld the sheets to the honeycomb or cells says Burling. ‘But of course surface preparations on the aluminium need to be addressed otherwise the long term durability will be suspect and corrosion can occur’
The Battrix energy storage concept is modular. Once the issues of joining the skins to the core (cells) have been addressed, the unit can then be used as the structural chassis of the vehicle.
‘If you fill the voids (cells) of the sandwich structure up with battery chemicals you then have the Battrix concept. There are a variety of combinations of different cell sizes which can be used, you can even have cells within cells. This could also protect the batteries in cases of impact/fire and cool cells individually improving their efficiency.
Ideally these batteries would be in the floor but could be in other sites of the vehicle, the roof, sides or wings, wherever there is space. It could even be put in the rear or the front wings of the vehicle where quite often the structure is built up using laminates on specialised vehicles.
The benefits of the Battrix concept for which TWI has applied for a patent include:
- Low weight
- High current transfer capability
- Exceptional thermal stability
- Environmentally friendly
- Easy recyclability
Battrix can be summarised as an electrical energy storage device such as an electromagnetic cell (battery) or a capacitor consisting of one or more inter-lockable structural cells that enables good current dissipation. This is achieved by way of increasing the surface area of the terminals of the device to enable a greater current flow and provide a structural element to a vehicle in the form of a chassis.
