Ultra Battery Feasibility - Investigation into the combined battery-supercapacitor for hybrid electric vehicle (HEV) applications

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The UltraBattery feasibility study aims to focus on the mechanisms behind the operation of an experimentally derived, Lead-Acid based Battery / Carbon Supercapacitor hybrid. This will allow accurate modelling of the device operation, permitting accurate state-of-charge (SoC) and State-of-health (SoH) estimations to be achieved for use, in Vehicle Management Units, as part of the overall vehicle energy management strategy. A model of the hybrid battery will be produced, possibly based on an extension of a 'Randles model' derived for Lead-Acid batteries. The investigation will include the possible use of maximal length sequences to derive the parameters for such a model, and the use of an observer based system to track the SoC of the hybrid battery. The investigation will encompass both bench testing of the hybrid battery for extraction of parameters, and simulations to quantify the effects of parameter variation and implement observer structures for model verification against practical test results. An important aspect of the project will be the instrumenting of a hybrid battery to attempt to measure the current distribution throughout the negative plate of the hybrid during both steady-state and dynamic operation, as the way the current splits between the supercapacitor section of the plate and the standard technology (battery) section of the plate will be critical in determining the operation and subsequent ability to model the hybrid battery, during both discharge and recharge under regenerative braking. The determination of the charge acceptance efficiency will inform energy management systems in order to maximise a vehicles energy management strategy, and hence maximise it's recapture of regenerative energy and minimise the CO2 emissions from the vehicle. The models developed within this project will also benefit the wider academic community, in that they may be embedded within a systems level simulator, for example the DoE's ADVISOR program, allowing full appraisals of the cheaper lead-based technology to be carried out within various vehicle scenarios.The success of the project, in understanding the operation of the hybrid lead-based battery will enable lead-based technology to be utilised in hybrid-electric vehicles (HEV), something which has to date been avoided as the high rate, partial state-of-charge (HRPSoC) operation of a battery within a HEV leads to rapid sulphation of the negative battery plate, and hence significantly reduced lifetime from the battery. As HEVs only require small capacity batteries, the extra weight penalty of using lead-based technologies will not be a significant burden, although the significantly reduced cost will be very attractive. An extra point to the use of lead-based technology is the fact that a lead re-cycling infra-structure is already in place, and Lead-acid batteries present virtually no explosion risk, unlike many of the competitor technologies (Li-ion, NiMH). The price advantage of the lead-based ultra-battery, fully supported by models and SoC estimation will have a significant impact on the production costs of HEVs and hence the market take-up with the subsequent reduction of CO2 from the vehicle sector.