Glacier Transportable Sampler - Isco

Glacier Transportable Sampler
Appendix D Battery Selection Guide
Glacier is programmed for continuous sampling, V c would be the
programmed bottle volume, provided that bottle-full detection is
being used. Use Figure D-1 to find A c by determining the
amp-hours for the average ambient temperature at your sampling
site.
Once the sample liquid has been cooled, more energy is required
to keep it cool. The second group in the equation may be used to
calculate the amp-hours required each day to keep the sample at
3° C. The number of days, D m , is the days from the first collected
sample to when the Glacier is no longer expected to keep the
sample cool. Use Figure D-2 to find A m .
The following scenario illustrates how to use the equation. Consider
a Glacier that is inhibited while waiting for an external
device to indicate that a measured condition, such as a rain
event, has occurred. The average ambient temperature is 30° C
(86° F). When the external device clears the inhibit, the Glacier
will collect sample volumes of 250 ml, once an hour, for 24 hours.
After running the program, it will take another day to retrieve
the Glacier and bring the composite sample to the lab.
From this example, we know that V c is 6 liters, D m is two days
(one to collect the samples, another to retrieve it), and the
ambient temperature is 30° C. At this ambient temperature,
Figure D-1 tells us A c is 25, and Figure D-2 tells us A m is 29. The
equation would be:
( )( )
V c x A c + D m x A m = Expected power consumption, Amp-hours
6
6 x 25
+ 2 x 29 = 83 Amp-hours
(
6
)( )
Using the equation we find operating the sampler under these
conditions would need a fully-charged battery with a capacity of
at least 83 amp-hours.
As previously mentioned, standby current is negligible. In the
example above, the Glacier could be waiting several days for the
rain event. Because the refrigeration system is not activated
until the first sample is taken, the number of days the Glacier is
inhibited is generally of no concern.
Figure D-1 assumes that the liquid temperature at the sampling
point is at room temperature (68 to 77° F or 20 to 25° C). Increase
or decrease the expected battery capacity accordingly if the
actual liquid temperature falls outside of this temperature range.
Other factors, such as high suction head heights (over 3 m or 10
feet) or the amount of direct sunlight will also affect the rated
current demand on the battery.
D-2