Page 133 - Lindens Handbook of Batteries

5.10 PRINCIPLES OF OPERATION

height, overall diameter, pip diameter, pip height, and diameter of negative cap. Maximum and mini-
mum values are usually specified, as shown in Fig. 5.11b. As these standards are revised periodically,
the latest edition should be used.

5.4 BATTERY CONSTRUCTION

The following constructional features should also be considered in the design and fabrication of
battery packs:
1. Intercell connections
2. Encapsulation of cells (should not inhibit vent activation)
3. Case configuration and materials
4. Terminals and contact materials

5.4.1 Intercell Connections
Soldering is the method of connection for batteries using Leclanché-type cells. Wires are soldered
between the negative case and the adjoining positive cap. This effective method of construction for
these cells is still widely used.
Welding of conductive tabs between cells is the preferred method of intercell connection for
most of the other battery systems. The tab materials for most applications are either pure nickel or
nickel-plated steel. The corrosion resistance of the nickel and its ease of welding result in reliable
permanent connections. The resistance of the tab material must be matched to the application to
minimize voltage loss. The resistance can be calculated from the resistivity of the material, which is
normally expressed in ohm-centimeters,

resistivity × length(cm)
Resistance =
2
cross-secttionalarea(cm )
The resistivity values of nickel and nickel-plated steel are

–6
Nickel 6.84 × 10 Ω ⋅ cm
–6
Nickel-plated steel 10 × 10 Ω ⋅ cm
For example, the resistance of a tab with dimensions of 0.635-cm width, 0.0127-cm thickness, and
2.54-cm length is
for nickel,
×
.
.
68410 6 - × 2 54 = 21510 Ω
3 -
×
.
×
.
0 635 0 0127
.
for nickel-plated steel,
×
.
10 10 6 - × 254
3 -
×
= 31510 Ω
.
×
0 635 0 0127
.
.
As is evident, the resistance of the nickel-plated steel material is 50% higher than that of nickel for
an equivalent-size tab. Normally this difference is of no significance in the circuit, and nickel-plated
steel is chosen due to its lower cost.