Factors Affecting A Decrease in Battery Life

849 WordsJul 10, 20184 Pages
It is difficult to compare accurately burn times/lighting durations between different manufactures hands-free lighting products since each manufacturer’s reference figures that show their product offering to have an advantage over competitive products. Some manufacturers state statistics of burn time calculated to times long after the emitted light output is useful (down to the last photon). Petzl clearly states it operates a policy whereby it ceases to consider a light effective when the lighting level (for standard hands-free lighting) decreases below 0.25 lux at a distance of 2 metres. This figure is selected as an approximate equivalence to the lux value generated on a dark night by a full moon. They consider this light output the…show more content…
Temperature of operation is a major factor that determines the possible burn time of a headtorch. All batteries depend on an electrochemical process whether charging or discharging and these chemical reactions are dependent on temperature. Nominal battery performance is usually specified for temperatures between 20°C and 30°C (Petzl test at 20°C) however performance can deviate substantially if not within this temperature range. As the ambient temperature rises, electron mobility increases thus increasing the batteries ability to deliver current values. This effect can be amplified by relative humidity surrounding the battery, which amplifies high temperature values. As temperature falls, so does the batteries ability to deliver current. At the upper end of the temperature range, the high temperatures may also initiate irreversible chemical reactions and electrolyte reduction, which can cause permanent damage or complete failure of the battery. At the lower end of the scale the electrolyte may freeze, although above the freezing point the chemical reaction may still be significantly slowed. The range of temperatures in which hands-free lighting devices are used, fluctuations will likely occur, however to what extent will depend on the user. Primary lithium batteries are very effective at maintaining effective operation at lower temperatures. How long since the battery was manufactured or recharged will influence
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