As a result of the work, several battery variants were produced for parameter, and full scale bench testing, as a 192 volt electric vehicle battery. The specific energy levels achieved by the batteries were in line with design considerations and very respectable by the standards of currently available commercial batteries. Unfortunately the cycle life of all variants was poor under the test procedures adopted.
This resulted in a change to the programme, so that a full scale investigation into the reasons for the poor cycle performance could be carried out. The reason for the failure was quite obviously severe softening of the positive active mass, but the cause of this softening was less easy to determine. Life cycling of a commercially available battery under the same test conditions produced a similar failure, whereas the same battery recycled under conditions by which the charge factor was controlled, gave considerably improved life. Thus it has been concluded that the method of charging was a major factor in the failure, although questions also remain over the ability of glass mat separators to retain their properties under compression, and thus adequately restrain the positive active material during cycling.
The proposed research is aimed at developing a fully recyclable, maintenance free lead-acid battery to meet the exacting demands of performance and life that will be required for passenger carrying vehicles. The work will seek to improve on currently achievable energy density levels and cycling performance of the valve regulated type of battery construction. In order to achieve these improvements it is anticipated that it may be necessary to incorporate some high value materials into the battery. Work will therefore be carried out on methods to recover these materials during the recycling operation.
The principal research tasks are:
a) Improvements in Active Material Utilisation
b) Extension of cycle life
c) Improvements to separator and grid alloy materials for valve regulated batteries
d) Recovery of the high value materials during the recycling process
e) Production of advanced lead-acid batteries for test by the Joint Research Committee of the European motor industry.
Successful completion of this programme will enable the battery industry to design and build quality, high performance, lead-acid batteries for Electric Vehicles which will be fully recyclable after use.
Funding SchemeCSC - Cost-sharing contracts
OX11 0RA Didcot
DA11 9BG Northfleet
BL5 1DD Bolton
36075 Montecchio Maggiore
LE16 9EZ Market Harborough