Linden D., Reddy T.B. (eds.) Handbook of batteries

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PORTABLE SEALED NICKEL-CADMIUM BATTERIES 28.27

FIGURE 28.31 Comparison of discharge characteristics of

sub-C size standard battery (A) vs. high-capacity battery (B)

on discharge at 20⬚C. Discharge at C rate, charge at 0.1C

rate for 16 hours.

FIGURE 28.32 Comparison of performance of standard

battery (A) vs. high-capacity battery (B) (sub-C size), at 20⬚C.

28.6.2 Fast-Charge Batteries

These batteries have electrode structures and electrolyte distribution designs to enhance ox-

ygen recombination. They can be charged at the fast 1-h rate with charge control (such as

temperature-sensing and

⫺⌬V techniques) and at the C/ 3 rate without charge control because

of their ability to withstand this level of overcharge. They are also capable of performance

at high discharge rates, though this is achieved at the expense of a slightly reduced battery

capacity. The batteries used in these batteries have improved internal heat conductivity, which

results in a faster increase in surface temperature. This feature can be used advantageously

in a temperature-sensing fast-charge system. Figure 28.33 shows the charge characteristics

of a fast-charge battery compared to a standard one. The internal gas pressure of the standard

battery increases quickly during charging whereas that of a fast-charge battery stabilizes.

28.28 CHAPTER TWENTY-EIGHT

FIGURE 28.33 Comparison of charge characteristics of fast-charge (solid line) bat-

tery vs. standard battery (broken line).

28.6.3 High-Temperature Batteries

These batteries are designed to operate at high temperatures without the service life deteri-

oration and charging inefﬁciencies experienced with conventional designs. Figure 28.34 com-

pares the performance of the high-temperature battery with the standard battery as a function

of ambient temperature during charge. This type of battery is capable of charge-discharge

cycling at temperatures as high as 35 to 45

⬚C and is particularly designed for trickle charging

(C/20 to C /50 rate) at these high temperatures. The charge voltage of these batteries is

slightly higher than that of the standard battery due to the designed-in control of the oxygen-

generating potential.

FIGURE 28.34 Comparison of performance of high-

temperature battery vs. standard battery. charge—C/ 30 rate;

discharge—1C rate at 20⬚C.

PORTABLE SEALED NICKEL-CADMIUM BATTERIES 28.29

28.6.4 Heat-Resistant Batteries

These batteries are designed for fast charging at high temperatures. For example, charging

at the 0.3C rate is possible even at temperatures as high as 45 to 70

⬚C. Their performance

characteristics are similar to those of the standard battery. However, they have a superior

service life when used at high temperatures because of the use of specially selected materials

with minimum deterioration at high temperatures. Figure 28.35 compares the service life for

standard and heat-resistant batteries throughout the temperature range.

FIGURE 28.35 Comparison of performance of heat-resistant battery

vs. standard battery.

28.6.5 Memory-Backup Batteries

These batteries are used to provide battery backup for volatile semiconductor memory de-

vices. The key requirements for this type of battery are long life (up to 10 years in certain

applications), low self-discharge, and good performance at low discharge rates. Figure 28.36

shows the storage characteristics of the memory-backup battery. (This can be compared to

the characteristics of the standard battery shown in Fig. 28.19.) The low-rate discharge

characteristics of the battery are plotted in Fig. 28.37. As the backup battery is designed for

low-rate use, its internal resistance is higher than that of the standard battery and its high-

rate discharge characteristics are not as good.

FIGURE 28.36 Storage characteristics of memory-backup

batteries.

28.30 CHAPTER TWENTY-EIGHT

FIGURE 28.37 Performance of memory-backup batteries.

Charge—C/ 30 for 48 h at 20⬚C. Discharge rate: (a) C / 10,000; (b)

C / 2000; (c) C/ 1000.

PORTABLE SEALED NICKEL-CADMIUM BATTERIES 28.31

28.6.6 Slim Rectangular Batteries

The constructional features of the slim rectangular battery are described in Sec. 28.3.3. The

advantage of the rectangular battery is that it permits more efﬁcient battery design, elimi-

nating the voids that occur with the assembly of cylindrical batteries. The volumetric energy

density of these batteries can be about 20% higher than a battery using a cylindrical design.

Most of the performance characteristics are similar to those of the standard cylindrical

battery, except that it also incorporates some of the features of the high-capacity battery. Gas

recombination has been improved to permit charging at the 0.2C rate or less and 1-h charging

with charge control, preferably with

⫺⌬V sensing. This is illustrated in Fig. 28.38. The

voltage proﬁle on discharge is ﬂat, as with the cylindrical battery, as shown in Fig. 28.39.

However, because the resistance of the rectangular battery is higher, performance at rates

greater than 4C are not as good as with the cylindrical battery. Storage characteristics and

cycle life are similar to those of the cylindrical battery.

FIGURE 28.38 Charge characteristics of slim rectangular batteries at 20⬚C. Charge—

1.5C rate; ⫺⌬V ⫽ 10 mV.

FIGURE 28.39 Discharge characteristics of slim rectangular batteries at

20⬚C. Charge—0.1C rate for 16 h.

28.32 CHAPTER TWENTY-EIGHT

TABLE 28.3 Speciﬁcations of Typical Sealed Nickel-

Cadmiuim Single-cell Batteries

Battery

size

Capacity

at 0.2C

rate, mAh

Dimensions, max., mm

Diameter Height Weight, g

Cylindrical batteries

Standard batteries: Charging—standard, 0.1C rate, 14–16 h;

quick, 0.3C rate, 4–5 h

AAAA

⁄

AAA

⁄

170

120

270

300

650

550

1450

1550

4400

4800

7700

12000

12.0

8.0

10.5

14.5

14.3

17.0

22.9

33.0

33.2

43.1

29.3

42.5

15.8

44.4

30.3

50.2

28.5

43.0

59.5

61.1

91.0

160

145

230

400

High-capacity batteries:

Charging—standard, 0.1C rate, 14–16

h; quick, 0.3C rate, 4–5 h

880

1150

650

1200

1550

1900

2400

5400

25500

14.3

17.0

22.9

33.2

43.1

50.3

28.5

43.0

50.0

59.5

146.1

150

700

28.7 BATTERY TYPES AND SIZES

Table 28.3 lists some of the types of sealed nickel-cadmium single-cell batteries that are

manufactured and some of their physical and electrical speciﬁcations. Multicell batteries are

also manufactured, using these cells, in a variety of output voltages and conﬁgurations.

Figure 28.40 is a guide to determining the approximate battery size required for a given

performance requirement or application. These data are based on the performance of a stan-

dard battery at 20 to 25

⬚C. Allowance must be factored into the estimate to determine the

performance under other discharge conditions.

Manufacturers’ data should be consulted for speciﬁc details on dimensions, ratings, and

performance characteristics as they may be different from those shown.

PORTABLE SEALED NICKEL-CADMIUM BATTERIES 28.33

TABLE 28.3 Speciﬁcations of Typical Sealed Nickel-

Cadmiuim Single-cell Batteries (Continued)

Battery

size

Capacity

at 0.2C

rate, mAh

Dimensions, max., mm

Diameter Height Weight, g

Cylindrical batteries

Fast-charge batteries: Charging—standard, 0.1C rate, 14–16 h;

quick, 0.3C rate, 4–5 h; fast, 1.5C rate, 1 h

⁄

550

1250

1400

1850

2000

3200

4300

17.0

22.9

26.0

33.0

28.5

34.0

43.0

42.9

50.0

59.5

160

High-temperature batteries:

Charging—standard, 0.1C rate,

14–16 h

650

1650

3100

4500

7700

12000

14.3

22.9

26.0

33.2

43.1

48.9

43.0

50.5

59.5

91.0

145

230

400

Heat-resistant batteries:

Charging—standard, 0.1C rate, 14–16

h; quick, 0.3C rate, 4–5 h

⁄

300

650

1350

1800

2200

14.5

14.3

22.9

26.0

30.3

50.2

43.0

42.9

50.0

Slim rectangular batteries

Capacity at

0.2 C rate,

mAh

Dimensions, max., mm

Height Width Thickness Weight, g

Slim rectangular batteries: Charging—standard, 0.1C rate,

14–16 h; quick, 0.3C rate, 4–5 h; fast, 1.5C rate, 1 h

450

650

900

1200

48.0

67.0

17.2

6.3

8.5

6.3

8.5

10.7

28.34

300

1650

4600

FIGURE 28.40 Selector guide for sealed nickel-cadmium cylindrical batteries. Guide can be used to deter-

mine approximate required battery size, given the load and desired run (service) time. Data based on fully

charged battery and 20

⬚C operating temperature.

PORTABLE SEALED NICKEL-CADMIUM BATTERIES 28.35

REFERENCE

1. Y. Sato, K. Ito, T. Arakawa and K. Kobaya Kawa ‘‘Possible Causes of the Memory Effect Observed

in Nickel-Cadmium Secondary Batteries. J. Electrochemical Society, 143:L225 (October 1996).

BIBLIOGRAPHY

Cadnica Sealed Type Nickel-Cadmium Batteries, Sanyo Electric Co., Osaka, Japan.

Ford, Floyd E.: Handbook for Handling and Storage of Nickel-Cadmium Batteries: Lessons Learned,

NASA Ref. Publ. 1326, Feb. 1994.

Nickel-Cadmium Batteries, Charge System Guide, Panasonic Industrial Co., Secaucus, N.J.

Nickel-Cadmium Batteries, Technical Handbook, Panasonic Industrial Co., Secaucus, N.J.

Sealed NiCad Handbook, SAFT Corp. of America, Valdosta, Ga.

Sealed Nickel-Cadmium Accumulators, Sales Program and Technical Handbook, Varta Batterie AG,

Hanover, Germany.

29.1

CHAPTER 29

PORTABLE SEALED NICKEL-METAL

HYDRIDE BATTERIES

David Linden and Doug Magnusen

29.1 GENERAL CHARACTERISTICS

The rechargeable sealed nickel-metal hydride battery is a relatively new technology with

characteristics similar to those of the sealed nickel-cadmium battery. The principal difference

is that the nickel-metal hydride battery uses hydrogen, absorbed in a metal alloy, for the

active negative material in place of the cadmium used in the nickel-cadmium battery.

The metal hydride electrode has a higher energy density than the cadmium electrode.

Therefore the amount of the negative electrode used in the nickel-metal hydride cell can be

less than that used in the nickel-cadmium cell. This allows for a larger volume for the positive

electrode, which results in a higher capacity or longer service life for the metal hydride

battery. Furthermore, as the nickel-metal hydride battery is free of cadmium, it is considered

more environmentally friendly than the nickel-cadmium battery and may reduce the problems

associated with the disposal of rechargeable nickel batteries.

Most of the operating characteristics of the sealed nickel-metal hydride battery on dis-

charge are similar to those of the nickel-cadmium battery. The sealed nickel-metal hydride

battery, however, does not have the very high rate capability of the nickel-cadmium battery.

In addition, the behavior of the two systems on charge, particularly on fast charge, is dif-

ferent. The nickel-metal hydride battery is less tolerant of overcharge and requires control

of the cutoff of the charge, which may not always be required for nickel-cadmium batteries.

During the past ﬁve years, the speciﬁc energy and energy density of the nickel-metal

hydride battery has been increased by over 35% as a result of improvements in both the

positive and negative electrodes. Concurrently, improvements were made in its high-rate

performance and cycle life. Because of its higher energy density and other comparable per-

formance characteristics, the nickel-metal hydride battery is replacing the nickel-cadmium

battery in computers, cellular phones and other consumer electronic applications with the

possible exceptions of high-drain power tools and applications where low battery cost is the

major consideration. However, the nickel-metal hydride battery now is being replaced, in

turn, by the lithium-ion battery which has an even higher speciﬁc energy and energy density.

The metal hydride battery in larger sizes is also being considered for use in applications

such as electric vehicles, where its higher speciﬁc energy and good cycle life approach

critical performance requirements.

The advantages and limitations of the sealed nickel-metal hydride battery are summarized

in Table 29.1. The main advantage of the nickel-metal hydride battery compared to the

nickel-cadmium battery is its higher speciﬁc energy and energy density.