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PG. 11
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the series voltage as shown in the picture below. Your batteries are dead if this measurement is less
than 2.8 Volts at room temperature, higher if at low temperature.
You may also use alkaline AA batteries such as Duracell Coppertop. They will not last nearly as
long, especially at low temperatures, but will likely be adequate for several weeks at 1-hour interval.
When replacing batteries use only fresh batteries. Don’t mix battery types. If one battery differs in
type or charge level from the other and the miniWIPER runs them to full discharge, then one battery
may leak.
Err on the side of caution when planning your deployment.
The recommended battery is the Energizer L91 lithium battery. For more information including the
performance at low temperatures, use this link: http://data.energizer.com/PDFs/l91.pdf
The figure (left) gives a general idea
of terminal voltage vs. lifetime.
Service life in hours is incorrect since
miniWIPER draws 50 to 100 mA
depending on various factors, but the
general shape of the voltage vs. time
gives an estimate of life remaining.
This plot is taken from the
manufacturer’s specification. The plot
is for a single battery. The
miniWIPER halts operation at a total
of 2.8 Volts.
B A T T E R Y L I F E E X A M P L E S
The several figures below show battery life tests for the very first wiper made. Tests were conducted
of a wiper installed on a miniDOT and so do not completely represent the C7 wiper but should be
similar. Tests were at 3 wipes per minute with 12-hour calibration (a miniDOT wipe feature) wipe
interval. All tests conducted at atmospheric pressure. Different wipers will have different endurance
due to differences in temperature, hydrostatic pressure, and the individual wiper's mechanical
friction. Please use a safety factor of 2 for shallow water and 4 for deep water when planning battery
life.
When evaluating the status of batteries from terminal voltage please remember the voltages
presented below vary with temperature and vary depending on how frequently the wiper is actuated.
The tests below are somewhat artificial since the wiper wipes very frequently in the tests compared
to expected field use.
Energizer L91 Lithium AA at room temperature. 12211 single scrub wipes.
