Specifications

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The largest concern with lithium ion batteries is their safety. This is a major
consideration of battery selection. Lithium ion batteries can be dangerous if
handled incorrectly. Explosion or fires can result, potentially causing personal
injury as well as damage to property. While many lithium ion battery packs on the
market today include circuitry to protect from the basic types of undesirable
power events that can cause a lithium ion cell to fail, it must still be handled and
charged correctly.
Indeed, many devices on the market today use lithium ion batteries, proving that
they can be used safely with the appropriate design considerations; it may be a
concern with this project. One possible dimensioned pack is shown in Figure
2.11.4-1. As mentioned previously, the user of this unit will have reduced
functionality if intoxicated. Therefore, the safety aspect of lithium ion must be
taken into account.
As far as weight and cost, both are within the limits set in the requirements.
However, the voltage spec is slightly out of the desired range. While the output
voltage will eventually be run through a voltage regulator to get output to a level
necessary by use by the other components, excessive voltage behind the
regulator is not desired as this would cause more heat in the regulator.
Although several special considerations must be made for lithium ion batteries
with respect to output power, overall safety, and charging considerations, its
advantages also make it a strong option for this project.
Figure 2.11.4-1: A 7.4V lithium ion battery pack. Reproduced with permission
from www.batteryspace.com
2.11.5 Lead Acid Battery