Page 141 - Battery Reference Book

Silver-cadmium secondary batteries 517
Table 5.4 Comparison of characteristics of Yardney Silvercell and Silcad batteries

Silvercel (silver-zinc) Silcad (silver-cadmium)
Energy output
W h/kg 88-110 48-75
W h/dm3 150-190 90-160
Open-circuit voltage 1.82-1.86 V 1.40 =k 0.04V
(70-100% charged)
Nominal voltage under load 1.5V 1.1 v
Plateau voltage regulation at 2% 5%
fixed load and f.5"C
Cycle life (dependent on model LR series: 150-300 cycles (3000 cycles under ideal
and usage conditions); typical 80-100 cycles conditions)
life to 80% of nominal HR series:
1 h rate, 15-20 cycles
30min rate, 10-15 cycles
10 min rate, 5- 10 cycles
6 min rate, single cycles
Operating life: wet shelf life LR series: 1-2 years 2-3 years
(varies with temperature and HR series: 6-12 months
state of charge)
Dry storage life Up to 5 years Up to5 years
Operating temperature range +73 to -21°C with heaters; optimum +73 to -21°C with heaters; optimum
performance 10-51 "C performance 10-51°C
Storage temperature range Wet: +37 to -47°C Wet: +37 to -47°C
Dry: +73 to -64°C Dry: +73 to -64°C
Operating attituda Any position except inverted; for Any position except inverted: for
optimum service, use upright optimum service, use upright
Internal resistance Very low, varies with cell model design Very low, varies with cell model design,
temperature and discharge rate temperature and discharge rate
Resistance to mechanical sress Excellent Excellent
Both types have met the stringent requirements of Spec. MIL-E-5272A and are
currently used in missiles, rockets, torpedoes and Moodspace applications;
extremely rugged, leakproof and spillproof, they can be packaged to meet the most
severe requirements
Charging times (dependent on 10-20 h 10-20 h
cell design)
Charge completion Sharp voltage rise at 2.0Vkell Sharp voltage rise at 1.55-1.6V/ceI1
Charge retention Up to 85% of nominal capacity after 3 Up to 85% of nominal capacity after 3
months' charged stand at room months' charged stand at room-
temperature temperature

costs (although silver costs are recoverable) and intro- required throughout a cycle life of 6- 18 months. This
duces security problems when compared to other bat- system also has an exceptional ability to retain its
tery systems such as lead-acid, nickel-cadmium, etc. charge during long periods of wet storage.
However, when space and weight are limiting factors, The major application for the low-rate series is
the silver-zinc system is a very attractive proposition. for service conditions where maximum energy density
The full range of characteristics of silver-cadmium and voltage regulation at low rates of discharge are
batteries is givlen in Table 5.5. required throughout a cycle life of 12-36 months. The
These batteries are available in high and low system also has an exceptional ability to retain its
rate versions (0.1-300Ah) and in modular packs charge during long periods of wet storage.
(2- 10 Ah) from Yardney ad other suppliers. Constant-current charging is recommended for sil-
The major application for the high-rate series is ver-cadmium batteries, with a charge rate of one-tenth
for service conditions where maximum energy density nominal capacity to 1.65 V/cel! or 1.55 V/cell mini-
and voltage regulation at high rates of discharge are mum. Alternatively, constant-potential charging can be