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

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.

The success of the proposed work will directly impact on the uptake of hybrid electric vehicles (HEVs), as the global impact of CO2 emissions from vehicles is well known, and the introduction of emissions targets in various countries is driving the interest in HEVs, an area which is considered essential in the development of the low carbon vehicle. The major obstacle to the uptake of HEVs is the extra cost of the currently used battery chemistries and conditioning electronics necessary to ensure correct operation of the system. The success of the proposed work will enable significantly cheaper energy storage systems to be made available to vehicle manufacturers, and hence the cost of HEVs to the general consumer will be much lower, assisting on the general uptake of the technology, and the lowering of vehicle emissions. A greater understanding of the interaction of the lead-carbon supercapacitor section of the UltraBattery with the standard Lead-acid part will not only aid the battery industry, but enable accurate SoC and SoH algorithms to be developed, with a knock-on effect of better engine / battery management units for vehicles, and more accurate information as to the energy available from the storage unit at any given time. The increased accuracy will not only inform the development of better energy management systems for vehicles, but improve consumer confidence in the technology. Most people have experienced the problem associated with a laptop or cell-phone which tells the user that it's fully charged then runs flat within 5 minutes. This problem is annoying on the scale of a laptop or cell-phone, but could have serious implications within the field of electric vehicles. (This problem arises as currently it is possible to have some estimate as to battery SoC, but not SoH, therefore any reduction in battery capacity goes un-noticed within the energy management system.) The proposed work will therefore impact a number of areas, both within HEVs and outside it, as the technology has a use within alternative energy for standby and islanded power applications. Publications produced by the work will impact the academic and industrial communities, and the IPR generated in the system models will be available to vehicle drive-train manufacturers for use in the vehicle management systems. The potential impact for the work is not only within the UK, but globally, as the reduction in CO2 from vehicles is an international problem. In addition, the technologies and models developed within this project will benefit the wider academic community, in that they may be embedded within a systems level simulator, for example the DoE's ADVISOR program. The investigators are well recognised within the field, and have good contacts within both the area of battery manufacture, as shown by the letter of support, and the automotive industry. Dissemination of the results will be both directly to interested parties, and via conference and learned society publications to the general academic community. The proposed project is limited to 18 months, long enough to allow meaningful testing of the technology and development of suitable models, but short enough to enable the conclusions to be disseminated to the marketplace in time to impact on the uptake of HEVs in the near future, hence lowering overall vehicle emissions.