Page 138 - Battery Reference Book

5/4 Silver batteries

Table 5.2 Performance characteristics of monovalent and of 1.20- 1.55 V. The battery operating temperature
divalent silver oxide-zinc primary watch cells (392 size) is -29 to +71T and, with water assistance, -48
to +71"C. The energy density is 11-66Whkg or
AgzO-Zn type Ago-Zn type 24-213 WWdm3, depending on battery size. Units are
available in the weight range 0.14-135 kg.
Energy density
W m-' 500 680
W hk-' 120 160 5.2 Silver-zinc secondary batteries
Voltage
Nominal 1.60 1.70 Work on the development of silver-zinc batteries
Working 1.50 1.50 began in 1942. This battery contains silver oxide as
Nominal rate the positive electrode and zinc as the negative elec-
Capacity mA/cm-2 initial 25 25 trode and has an alkaline electrolyte. This combination
Backlight pulse results in what is, for alkaline batteries, a very high
constant discharge voltage of approximately 1.8 or
at 80% DOD 10 15 1.5 Vlcell respective to the two-step voltage discharge
Life, capacity characteristic of silver-zinc batteries.
mA h-' per cell 38 52 Rechargeable silver-zinc batteries can provide
Service years higher currents, more level voltage and up to six
LCD 2.17 2.97 times greater ampere hour capacity per unit weight
LCD backlight pulse 1.52 2.08 of battery. Thus, depending on the type of silver-zinc
analogue battery and by whom it was manufactured, one can
Shelf life (years) 5 5 obtain 70- 120 W h/kg (as batteries) or 55- 120 W hkg
Temperature ("C) (as cells) (theoretical value 440Whkg) for a
Storage -40 to 60 -40 to 60 silver-zinc battery compared to 30Whkg for a
Operation -10 to 55 -10 to 55 lead-acid battery and 25-3OWhkg for a nickel-zinc
Capacity loss per or a nickel-cadmium battery (Figure 5.1). Similarly,
annum at 21°C (%) 3 4 the silver-zinc battery gives appreciably greater
volumetric outputs (Wh/dm3) than the other types
of battery. Eagle Picher, for example, produce
electrolyte under pressure. In addition to a unit contain- units with a practical volumetric energy density of
ing dry charged plates they also contain an electrolyte 50-415WWdm3 as cells and 55-262Wh/dm3 as
vessel from which the cells are filled by electrical or batteries. These are thus an attractive type of battery
mechanical means. Pile batteries are a new develop- in circumstances where space availability is low or
ment of remotely activated primary batteries which battery weight has to be kept low, and where the power
confer a very high density on the battery. output requirement is high. Because it can generate
The battery has no moving parts. It has an extended the same amount of electrical energy as other battery
shelf life. It can be activated directly into a load or in systems, in packages as little as one-fifth of their
parallel with a mains system. The open-circuit voltage weight, the silver-zinc battery provides a long-sought
of this battery is 1.6-1.87V with a working voltage answer to the design engineer's critical need for space

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