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PG. 10
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Keep the sensing foil out of direct sunlight for extended periods of time.
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 of a month or two, then
alkaline batteries will provide adequate performance. For longer deployments, or for deployments in
cold environments, then substitute lithium batteries.
A A L I T H I U M B A T T E R Y L I F E
The miniDOT Clear Logger consumes battery power mostly from the measurement of dissolved
oxygen, but also slightly from simply keeping track of time, writing files, sleeping, and other activities.
The following table shows the approximate endurance of the miniDOT Clear Logger when powered
by the Energizer L91 AA lithium / ferrous disulfide batteries:
Sample Interval
(Minutes)
Main AA Battery Life
(Months)
Number of Samples
1
12
500K
10
>12
>52,000
60
>12
>8,000
Keep a general record of the miniDOT Clear
Logger’s number of samples. It is not possible to
accurately tell the charge state of a lithium battery by measuring its terminal voltage. If you have a
general idea of the number of samples already obtained on a battery, then you can make a guess as
to how many more samples remain.
The numbers in the table above are, at the time of this writing, based upon extrapolations of testing
of 500K samples acquired at a 5-second interval. The 1-year performance at 1 minute is very likely.
Performance at longer sample intervals will be much longer, but how long is difficult to predict. In any
event, these AA batteries are easily available and relatively inexpensive compared to the cost of the
miniDOT Clear Logger. PME suggests you replace the batteries often, especially before any long
(months) measurement deployments.
Monitor battery voltage in the miniDOT Control program. 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.
