Page 591 - Battery Reference Book

Nickel-cadmium secondary batteries 51/29
When charged they should be handled with care to
avoid short-circuits because the short-circuit current is
very high. When storing for more than 6 months a
storage temperature lower than 15°C is recommended
by the manufacturers. -
Figure 51.21 shows the effect on delivered capa- 9 0.8
city of KR cells of two of the factors that have 0.7
most influence on capacity, namely current and cell U
temperature. The available capacity decreases at high 0.2 0.4 0.6 0.8 1.0 1.2 1.4 A
currents and/or low temperatures. This is shown by
the typical discharge curves for 25, 0 and -18°C Figure 51.22 Capacity and final voltage versus discharge current
for a Nife Jungner sealed nickel-cadmium cell type KR 15/51,
in Figure 5 1.21. Maximum recommended continuous 0.4Ah (Courtesy of Nife Jungner)
discharge current differs for different cell sizes. It
ranges from 3.5 to 5 C A. Considerably higher current
can be used at short discharges (see Table 51.30). Marathon (USA)
Figure 51.22 shows the relationship between dis- Marathon supply a range of vented rechargeable 1.25 V
charge current and capacity and final voltage for a KR sealed cells in the capacity range up to 53Ah, and
15/51 0.4Ah cell. also made-up batteries to customers' specifications
(see Table 51.31). These batteries are equipped with
a pressure relief vent. It is claimed by Marathon
1.3 that these cells can be charged using a simple trans-
1.2 former-rectifier circuit, that they can safely be left on
- overcharge for months, if necessary, and that they have
5 1.1
0 1.0 thousands of hours of life. Performance characteristics
E 0.9
- of these batteries are given in Table 51.28.
3 0.8
General Electric Corporation (USA)
General Electric manufacture a very wide range of
1 1 1 1 1 1 1 1 1 1 1 1 1 1 ,
0.1 0.2 0.3 0.4 rechargeable sealed nickel-cadmium cells, including
Capacity (A h) cylindrical, oval and rectangular cells, and also the
(a) 25 'C Perma-cell, which is offered as an alternative to
primary cells. Each of the three types of cell has
1.3 its own typical applications (Table 5 1.32). Thus cylin-
- 1.2 drical, rectangular and oval cells are recommended for
- portable appliances and tools, photographic equipment,
> 1.1
g 1.0 business machines, communications equipment, toys,
- i? 0.9 hobby equipment, heating and lighting, while Perma-
3 0.8 cells are recommended for calculators, tape recorders,
toys, flashlights, photoflash equipment, etc. General
Electric also supply special aerospace cells.
I I I I 1 I
0.05 0.10 0.15 0.20 0.25 0.30 A range of extended-capability cells are available
Capacity (A h) in three types. Goldtop cells are for normal charge
rates and are capable of operating at cell temperatures
(b) 0°C up to 65°C. These cells are suitable for applications
1.3 requiring long cell life at high ambient temperatures
- 1.2 and/or high cell temperatures caused by continuous
>
- 1.1 long-term overcharge. The second type of Goldtop
(u 0.04 A
p 1.0 cells are for use at quick charge rates where continuous
c
;5 0.9 overcharge rates of 0.3C are combined with high
>
0.8 operating temperatures.
Power-Up-15 cells are supplied for use with Power-
I I Up-15 battery charger systems that charge the cell or
0.05 0.10 0.15 0.20 0.25 0.30 battery at fast charge rates of 1.0-4.OC. These cells
Capacity (Ah)
have voltage/temperature versus state of charge char-
(c) -18°C acteristics that permit effective control, using circuits
that sense both battery temperature and voltage. The
Figure 51.21 Discharge voltage versus capacity (at the stated
temperature) ol' Nife Jungner KR 15/51 sealed nickel-cadmium charge is thus terminated by either voltage or temper-
cells, 0.4Ah capacity (Courtesy of Nife Jungner) ature, permitting reliable fast charging.