Page 74 - Handbook of Battery Materials

40 2 Practical Batteries

1.6 Charge

1.4
Cell voltage/V 1.2

1.0
0.8 Ni-Cd Ni-Cd
(Standard) (high-capacity) Ni-MH
0.6
Discharge
0 400 800 1200 1600 2000
Charge-discharge capacity /mAh

Figure 2.20 Charge–discharge characteristics of an Ni–MH battery (cell type AA).
1.5 60 6
Charging:0.1C
Temperature:25°C
1.4 Battery voltage 50 5
Battery voltage (V) 1.3 Battery temperature 40 Battery temperature (°C) 4 Internal gas pressure (kgf/cm 2 )

3
1.2
30
1.1
Internal gas pressure 20 2
1.0 10 1

0 0
0 20 40 60 80 100 120 140 160 180
Amount of charging (%)

Figure 2.21 General charging characteristics of an Ni–MH battery (cell type 4/3 A).
current under 3 C. Figure 2.23 shows the charge–discharge characteristics. A life
of 1000 cycles was obtained.
The outstanding characteristics of the nickel–MH battery are as follows:

1) A discharge capacity 80% higher than that of the standard nickel–cadmium
battery;
2) A low internal resistance, which enables high-rate discharge;
3) A long charge–discharge cycle life, which can exceed 1000 cycle, and cell
materials which are adaptable to the environment.
Since nickel–MH batteries were commercialized in 1990, they have become
increasingly popular as a power source for computers, cellular phones, electric
shavers, and other products.
The high capacity of the nickel–MH battery, which is approximately twice that of
a standard nickel–cadmium battery, is possible because a hydrogen-absorbing alloy