Objective
Objectives and content
This Project is designed to follow, and build upon, the
results achieved in Project BE 7297. While still
incomplete, certain key outcomes of the research can be
stated;
At the high rates of discharge experienced in EV
applications, active material utilisation is limited by
acid availability rather than paste conductivity. Thus
there is limited scope for improvements to specific by
additives to the positive active mass.
Key factors in the improvement of cycle life of the
valve-regulated (maintenance-free) lead-acid battery have
been shown to be, compression of the active mass by the
separator, the construction of the absorptive glass mat
separator and the nature of the charge regime employed to
recharge the battery after use.
It has been possible to enhance considerably, the
properties of the grid alloys used (strength and
corrosion resistance) by additions of tin and silver.
Work elsewhere has shown that rapid charging techniques,
as well radically reducing recharging times, can improve
cycle life of flat plate batteries apparently by
modifying active material structure. Such techniques can
however result in elevated temperatures in the battery,
which can be detrimental to negative plate life. Also
certain test regimes for EV batteries have demonstrated
that the negative plate can fail under the influence of
repeated and prolonged high-rate discharge pulses.
Accordingly the work in the Project will focus in three
areas;
The improvement of specific energy and life of leadacid batteries by the development of light-weight tubular
designs using the high-strength, corrosion resistant
alloys mentioned above. In this type of battery, the
positive active material is constrained between the alloy
spine and a porous fabric gauntlet, thus reducing
opportunities for paste shedding on softening during
cycling. Operating this type of battery under
compression, in an AGM design, will help to maintain
electronic conductivity within the active material,
especially with the lower paste densities required for
higher utilisation. Rapid charging techniques will also
be tried on these designs.
The study of separator compression across the plate
stack as a whole to determine the reasons for the early
initial loss of capacity experienced in these designs.
Several different separator designs will be studied to
overcome problems of acid stratification and relaxation
of compression during service.
The mechanism of the degradation of the negative plate
will be studied under conditions of electric vehicle
service and, following this, work will be carried out to
develop improved expander additives for the maintenance
of the required open structure in the negative active
mass.
The work is expected to result in further improvements to
cycle life and specific energy of the lead-acid battery
and a consequent reduction in running costs. This will
in turn make the performance and cost of an electric
vehicle more attractive and hence improve their
marketability. This will be done with out detriment to
the current inherent good recyclability of the lead-acid
battery.
Fields of science
Topic(s)
Call for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
W1N 3LQ London
United Kingdom