TABLE OF CONTENTS Joseph A. Carcone
Sealed nickel-cadmium batteries incorporate specific battery design features to prevent a buildup of pressure in the battery caused by gassing during overcharge. As a result, batteries can be sealed and require no servicing or maintenance other than recharging. These unique characteristics for a secondary battery have created wide acceptance for use in a variety of applications, ranging from lightweight portable power (photography, toys, housewares) to high-rate, high-capacity power (electronic devices such as phones, computers, camcorders, power tools) and standby power (emergency lighting, alarm, memory backup). Some nickel-cadmium batteries are now incorporating smart battery control circuitry to give state-of-charge indication and to control overcharge and overdischarge (see Chap. 5).
The major advantages and disadvantages of the sealed nickel-cadmium battery are summarized in Table 28.1. The important characteristics are described in this section.
| Advantages | Disadvantages |
|---|---|
| Batteries are sealed; no maintenance required | Voltage depression or memory effect in certain applications |
| Long cycle life | Higher cost than sealed lead-acid battery |
| Good low-temperature and high-rate performance capability | Poor charge retention |
| Sealed lead-acid battery better at high temperature and float service* | |
| Long shelf life in any state of charge | |
| Rapid recharge capability | Environmental concern with the use of cadmium |
| Lower capacity than other competitive batteries | |
| *High-temperature nickel-cadmium batteries are available (see Sec. 28.6.3). See Sec. 28.4.11. |
Maintenance-free operation: The batteries are sealed, contain no free electrolyte, and require no servicing or maintenance other than recharging.
High-rate...
