Page 446 - Battery Reference Book

Other power sources for vehicle propulsion 43/5
material in the tube reduces losses of active mater- of thinner cross-section and greater oxidation res-
ial which usually occurs with increase of utilization. istance are now being produced from polyethylene
Elecbic vehicle batteries are usually assembled in 6 V and polypropylene, which offer the advantages of
monobloc units thereby improving energy density. decreased weight and volume, and increased res-
The General Motors G-Van, now marketed, has a istance to oxidation degradation during overcharge.
range of 90km In simulated city driving conditions These materials, in conjunction with cellulosic films,
with a top speed of 52mph and acceleration from 0 or alone, can increase energy densities and life.
to 30mph in 13 seconds. Problems with this battery The utilization of the nickel-zinc system for elec-
are associated with a loss of power capability as the tric vehicle propulsion is dependent on the realization
battery is discharged. of cycle life in excess of 500 deep cycles. Currently,
The General Motors ImpactTM lightweight car cycle life is limited by the zinc electrode; specifi-
(39101cg gross weight) can accelerate from 0 to 60 mph cally, the phenomenon known as zinc shape change.
in 8 seconds and has a top speed of 100 mph. It is fitted Work is currently being done at Eagle Picher which
with 32 10 V 42 Ah batteries weighing 400 kg, giving has demonstrated a capability to achieve 300 cycles
a total output of 13.6 kW h. at a 65% depth of discharge. This performance is
based on an improved separator system, controlled
charging methods, and incorporation of construction
43.2 Ot ower sources for vehicle features designed to minimize zinc electrode shape
propslls change. Further improvements are anticipated in the
zinc electrode based on construction features designed
43.2.1 Nickel!-cadmium to control the concentration gradients of dissolved zinc
Nickel-cadmium batteries are used extensively in ionic species within the cell.
France for electric vehicle propulsion, e.g. by Renault An interesting cost trade-off for the nickel-zinc
and Peugeot. system is available concerning the nickel electrode.
The ultimate design objective is, of course, to develop
a deep cycling capability upwards io 1000 cycles.
3.2.2 The nickel-zinc battery system However, if a much lower cycle life can be tolerated
(200-250 cycles), it is possible to construct cells with
The nickel-zinc system is a viable candidate for elec- non-sintered nickel oxide electrodes at a lower cost.
tric vehicle propulsion based on its high energy density Comparative cost and performance data for
and power density. The voltage is 1.85V at 25°C. nickel-hydrogen, nickel-iron and nickel-zinc sys-
The zinc electrode contributes a high electrode poten- tems are given in Table 43.1.
tial and a low equivalent weight, resulting in energy Yuasa, Japan have been developing prototype
densities of 706;Vhkg presently obtainable in a con- nickel-hydrogen batteries for electric vehicle applica-
figuration suitable for an electric vehicle application. tions. They have claimed 200 maintenance free cycles
Other features of the system that make it attractive for at 100% depth of discharge.
electric vehicles are:
1. The capability of accepting either constant-potential
or constant-current charging with little overcharge 43.2.3 Lithium aluminium alloy-iron
required. sulphide batteries for vehicle propulsion
2. The potential of operation as a sealed, maintenance-
free unit. Eagle Picher entered into the development of the
3. The ability to withstand considerable overdischarge lithium-metal sulphide battery system for vehicle
without cell reversal, owing to the excess of zinc propulsion in 1975. The electrochemical system under
oxide active material. study utilizes an anode of a lithium-aluminium alloy
and a cathode of the metal sulphides. Iron sulphide
Separator systems for nickel-zinc cells have exten- (FeS) or iron disulphide (FeS2) is currently most com-
sively employed cellulosic materials. New materials monly utilized. Initial efforts were directed toward

Table 43.1 Nickel battery systems cost and performance summary
Nickel-hydrogen Nickel-iron Nickel-zinc
Energy density at 2h rate (W hkg) 60 SO 70
Cycle life (100% depth of discharge) (cycles) 2000 2000 500
Power density (minimum) (Wkg) 100 100 150
Battery costs (SkW h) 100-200 so-100 50-100
Costskycle ($kW h) 0.05-0.10 0.03-0.05 0.10-0.20