Page 130 - Battery Reference Book

4/14 Nickel batteries
presently developed technology offers to the user a bat-
tery with high specific energy, low maintenance, deep
discharge capability and long cycle life. Full-scale
electrodes have exceeded 1300 deep discharge cycles.
Full-scale cells as well as 6 V modules have been fab-
ricated and show no capacity fade under 100% depth- 2 Charge Discharge
-
of-discharge cycling. Energy efficiencies are typically - Cl5 rate C13 rate
70% or greater (see Table 4.9). 6 0.5
I I I I t
Table 4.9 Nickel-iron battery performance 0 50 100 50 0
State of charge (Om\
1980 to present Goals
state of the art Figure 4.12 Nickel-iron cell chargeldischarge profile (Courtesy
of Eagle Picher)
Specific energy at battery
level (W hkg) 50 60 1.50 c
Energy density at battery
level (W M) 102 120
Specific peak power at
battery level (Wkg) I10 125
Deep discharge (100%)
cycle life 1000 2000
--- (73.5 discharge
2 0.75
Figure 4.12 shows the voltage profile for a single - --.- C11.5 discharge
- U0.75 discharge
nickel-iron cell tested to the constant current modes
as indicated.
The set of discharge curves shown in Figure 4.13
was taken from actual tests of a 280Ah cell. Note
the retention of capacity at the higher discharge rates,
indicating the good power characteristics of this type
of battery. The 6 V modules shown in Figure 4.14 have
been fabricated by Eagle Picher, and placed under
test. Nominal capacities of these modules are 280 Ah
when discharged at the 3 h rate. Nominal operating
voltage is 6.15V. Capacities of these modules have
been stable under 100% depth of discharge (DOD)
cycling. Cycle life has presently reached 300 cycles
as testing continues. Energy densities are 50 W hkg
and 102 W h/l respectively, with an energy efficiency
of 70% or greater. A return factor of 110% has been
established as the most optimum for the nickel-iron
system with respect to required maintenance. Tests to
date show no thermal problem to exist with the cur-
rently established design when the module is subjected
to the expected vehicle driving profile.
The nickel-iron system may suffer the disadvan-
tage of being a vented system, which will require
periodic maintenance. However, the cost advantage
is significant in this system’s favour. Combining a
projected cost of $50- lOOkWh with extremely long Figure 4.14 280A h nickel-iron electric vehicle battery (Courtesy
cycle life, this system could offer an economical type of Eagle Picher)
of battery for use in electric vehicles.
become competitive with the more familiar battery sys-
4.3 Nickel-zinc secondary batteries tems. It has a good cycle life and has load-voltage
characteristics higher than that of the silver-zinc sys-
With the development of new types of separator tem. The energy available per unit weight and volume
and zinc electrodes, the nickel-zinc battery has now are slightly lower than those of the silver-cadmium