Page 124 - Lindens Handbook of Batteries

CHAPTER 5

BATTERY DESIGN

Daniel D. Friel

5.1 GENERAL

Proper design of the battery pack or the battery compartment is important to assure optimum, reli-
able, and safe operation. Many problems attributed to the battery may have been prevented had proper
precautions been taken with both the design of the battery itself, any battery monitoring or protection
devices or electronics, and how the battery pack is designed into the battery-operated equipment.
It is important to note that the performance of a cell in a battery can be significantly different
from that of an individual cell depending on the particular environment of that cell in the battery.
Specifications and data sheets provided by the manufacturers should only be used as a guide as it is not
always possible to extrapolate the data to determine the performance of multicell batteries in a series/
parallel configuration in a battery pack. Such factors as the cell uniformity, number of cells, series or
parallel connections, battery case material and design, conditions of discharge and charge, and tempera-
ture, to name a few, influence the performance of the battery. The problem is usually exacerbated under
the more stringent conditions of use, such as high-rate charging and discharging, operation, and extreme
temperatures and other conditions that tend to increase the variability of the cells within the battery.
Higher series/parallel configurations also present unique challenges which must be considered.
Further, specific energy and energy density data based on cell or single-cell battery performance have
to be derated when the weight and volume of the battery case, battery assembly materials, and any ancil-
lary equipment, such as monitoring or protection electronics, have to be considered in the calculation.
Another factor that must be considered, particularly with newly developing battery technologies,
is the difficulty of scaling up laboratory data based on smaller individual batteries to multicell bat-
teries using larger cells manufactured on a production line.
This chapter will address the issues that the product designer should consider. Cell and battery
manufacturers should also be consulted to obtain specific details on their recommendations for the
batteries they market.

5.2 DESIGNING TO ELIMINATE POTENTIAL SAFETY PROBLEMS

Batteries are sources of energy and when used properly will deliver their energy in a safe manner.
There are instances, however, when a battery may vent, rupture, or even explode if it is abused. The
design of the battery should include protective devices and other features that can prevent, or at least
minimize, the problem.
Some of the most common causes for battery failure are:
1. Short-circuiting of battery terminals
2. Excessive high rate discharge or charge

5.1