Page 305 - Lindens Handbook of Batteries

BUTTOn CELL BATTErIES: SILVEr OxIDE–ZInC AnD ZInC-AIr SYSTEmS 13.11

13.4 PERFORMANCE CHARACTERISTICS

13.4.1 open-Circuit voltage

The open-circuit voltage (OCV) of the Zn/Ag O battery is about 1.60 V, but will vary slightly (1.595
2
to 1.605 V) with electrolyte concentration, concentration of zincate in the electrolyte, and tempera-
25
ture exposure. The reaction of the silver oxide with carbon dioxide during battery manufacturing
can raise the OCV to 1.65 V due to the formation of silver carbonate. The increase in voltage, how-
ever, is temporary and will drop to the operating voltage level of 1.58 V within seconds, for example,
in a watch. The depth of discharge has little effect on the OCV of a monovalent silver battery; a
partially used battery has the same OCV as a new one.
The OCV of the zinc/divalent silver oxide battery will vary from 1.58 to 1.86 V, depending on
the ratios of Ag to Ag O to AgO in the cathode. The OCV will decrease with greater Ag O to AgO
2
2
ratios and with the presence of silver metal in the cathode. With divalent silver oxide batteries, the
depth of discharge does have an effect on the OCV; a partially used battery will have more Ag O and
2
silver metal than a new one and may have a lower OCV.
13.4.2 discharge Characteristics

Figure 13.10 exhibits the typical curves for a type 389, 11.6 × 3.0 mm monovalent silver oxide bat-
tery on constant resistance discharge. These are typical voltage curves; the discharge voltage profiles
of other size batteries would be similar. The service life will vary depending upon the size of the
battery and the applied load.
The discharge characteristics of the various types of silver oxide batteries are also covered in
Sec. 13.2.2.
Figure 13.11 shows the initial closed-circuit voltage of representative sizes of zinc/silver oxide
batteries at various loads and temperatures. The zinc/silver oxide button battery is capable of oper-
ating over a wide temperature range. The battery can deliver more than 70% of its 20°C capacity
at 0°C and 35% at -20°C, at the more moderate loads. At heavier loads, the loss is greater. Higher
temperatures tend to accelerate capacity deterioration, but temperatures as high as 60°C can be toler-
ated for several days with no serious effect.

FiGURE 13.10 Typical discharge curves of zinc/silver oxide battery at
20°C, type 389 button cell 11.6 × 3.0 mm.