Page 290 - Lindens Handbook of Batteries

12.10 PRIMARY BATTERIES

12.5.4 Impedance
Impedance for the zinc/mercuric oxide button batteries was usually measured at a frequency of
1 kHz because of their use in hearing-aids. 9
The impedance curve is almost a mirror image of the voltage discharge curve, rising very
steeply at the end of the useful discharge life, as illustrated in Fig. 12.10. The value obtained is
frequency-dependent to some degree, particularly above 1 MHz, and a fixed frequency has to be
specified. A frequency versus impedance curve under no-load conditions is shown in Fig. 12.11.

10 1.5
9 1.4
8 7 1.3 Voltage
Impedance, ohms 6 5 Battery voltage, V 1.1
1.2

1.0

0.8
3 4 0.9
Impedance
2 0.7
1 0.6
0.5
0 4 12 20 28 36 44 52 60 68 76 84
Hours of discharge
FIGURE 12.10 Internal impedance, zinc/mercuric oxide battery,
350 mAh size, 20°C, 1 kHz, 250 ohms load.

3.4

3.0
Impedance, ohms 2.2
2.6

1.8
1.4

1.0
0.1 1.0 10.0 100.0 1000.0
Frequency, kHz
FIGURE 12.11 Variation of impedance with frequency, zinc/mercuric oxide battery,
210 mAh size, 20°C.