Page 103 - Lindens Handbook of Batteries

3.22 PRINCIPLES OF OPERATION

3.2.13 Effect of Battery Design
The performance of the cells in a multicell battery will usually be different than the performance of
the individual cells. The cells cannot be manufactured identically and, although cells are selected to
be “balanced,” they each encounter a somewhat different environment in the battery pack.
The specific design of the multicell battery and the hardware that is used (such as packaging
techniques, spacing between the cells, container material, insulation, potting compound, fuses and
other electronic controls, etc.) will influence the performance as they effect the environment and
temperature of the individual cells. Obviously, the battery materials add to its size and weight, and
the specific energy or energy density of the battery will be lower than that of the component cells.
Accordingly, when comparing values such as specific energy, in addition to being aware of the
conditions (discharge rate, temperature, etc.) under which these values were determined, it should
be ascertained whether the values given are for cells, single-cell batteries, or multicell batteries.
Usually, as is the case in this Handbook, they are on the basis of a single-cell battery unless speci-
fied otherwise.
Battery designs that retain the heat dissipated by the cells can improve the performance at low
temperatures. On the other hand, excessive buildup of heat can be injurious to the battery’s perfor-
mance, life, and safety. As much as possible, batteries should be thermally designed to maintain a
uniform internal temperature and avoid “hot spots.”
In the case of rechargeable batteries, cycling could cause the individual cells in a battery peak to
become unbalanced and their voltage, capacity, or other characteristics could become significantly
different. This could result in poor performance or safety problems, and end-of-charge or discharge
control may be necessary to prevent this. Cell balancing techniques are employed with some sys-
tems, such as lithium-ion batteries.
The influence of battery design and recommendations for effective battery design are covered in
Chap. 5.
Several recent papers review the current status and future prospects for improvements in battery
performance. 4,5

REFERENCES

1. R. Selim and P. Bro, “Performance Domain Analysis of Primary Batteries,” Electrochemical Technology,
J. Electrochem. Soc. 118(5):829 (1971).
2. D. I. Pomerantz, “The Characterization of High Rate Batteries,” IEEE Transactions Electronics, 36(4):954
(1990).
3. P. Ruetschi, “Alkaline Electrolyte-Lithium Miniature Primary Batteries,” J. Power Sources, 7(1982).
4. M. Winter and B. Brodd, Chem Revs. 104:4245–4270 (2004).
5. D. Linden and T. B. Reddy, Battery Power and Products Technology, 5(2) (March/April 2008).