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PG. 10
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1970. This may be inconvenient in some cases. If so, use the
miniWIPERConcatenate program which not only concatenates all the files, but also adds more
readable statements of the time stamp.
Please refer to Chapter 2 for instructions on operating the miniWIPERConcatenate program.
The miniWIPER requires time and battery energy to work through the file directory on the SD card to
allocate new file space. A few hundred files on the SD card is not a problem, but as the number of
files grows large into the thousands then the miniWIPER may suffer decreased battery life or other
performance problems. Please, at the earliest convenient time, copy the recorded files to a
HOSTcomputer and delete them from miniWIPER's SD card. Also, do not use miniWIPER to store
files unrelated to the miniWIPER’s operation.
A A A L K A L I N E B A T T E R Y L I F E
Alkaline batteries will give somewhat less performance than lithium, especially at low temperatures.
Alkaline batteries are superior to lithium in one way: you can determine how much battery life
remains by measuring the battery terminal voltage. For short deployments alkaline batteries will
provide adequate performance. For longer deployments, or for deployments in cold environments
substitute lithium batteries.
A A L I T H I U M B A T T E R Y L I F E
The miniWIPER consumes battery energy mostly from operating the wiper motor, but also slightly
from simply keeping track of time, writing files, sleeping, and other activities. The amount of energy
consumed at each wipe depends on the friction in the mechanical system, on the hydrostatic loading
of the wiper shaft, and especially on the environmental temperature. Unfortunately, deep
deployments also tend to be cold, which is the worst case.
At the time of this writing it appears that about 10K wipes can be obtained in shallow warm water. At
25-meter depths we estimate about 8K wipes in warm water. Cold temperatures change battery
performance substantially. A safety factor of 2 should be applied. At present we recommend
deployments be for no longer than 3 months or 2K wipes.
miniWIPER records battery voltage and the number of wipes. It is not possible to accurately tell the
charge state of a lithium battery by measuring its terminal voltage since this voltage responds to
battery temperature. If you have a general idea of the number of wipes already obtained on a
battery, then you can make a guess as to how many more wipes remain.
Monitor battery terminal voltage. You cannot tell from terminal voltage of a lithium battery how long
the battery will last, but you can tell if it will die soon. The Low Drain Performance plot below gives
an estimate of terminal voltage for both lithium and alkaline batteries. Your measured voltage will be
2X what is shown below since there are two batteries in series within the miniWIPER. You can
operate batteries down to about 2.8 Volts (for two in series, 1.4 Volts on the graph below). Measure
