Glacier Transportable Sampler - Isco

Glacier Transportable Sampler
Appendix D Battery Selection Guide
D.1 Introduction This section provides information to assist with selecting a power
source for 12 VDC battery-powered Glacier Samplers. Teledyne
Isco recommends deep-cycle marine batteries, although any 12
VDC power source will work provided that it can meet the
current demands of the refrigeration system.
D.2 Determining the
Power Consumption
The Glacier requires continuous 12 VDC power for several purposes:
• an idle current while the sampler is inhibited, waiting
for the next sample, or after it has finished its sampling
program
• logging temperature readings at one-minute intervals
• operating the pump
• cooling the sample container.
The first three are negligible when compared to the energy
required to cool the liquid as it is collected and to maintain the
composite sample at 3° C.
The amount of energy required to cool the samples correlates to
ambient air temperature. The higher the air temperature, the
more the Glacier must operate the refrigeration system.
The equation below may be used as a guide for selecting a
battery that will meet the requirements of your sampling
program.
V c x A c + D m x A m = Expected power consumption, Amp-hours
(
6
)( )
Where:
V c = Total sample volume, in liters
A c = Amp-hours to cool sample liquid from 20° C (Fig D-1)
D m = Number of days sample volume must be maintained
A m = Amp-hour per day factor for maintenance (Fig D-2)
Before using the equation you must know:
• the total sample volume that will be collected
• the number of days that the Glacier must keep the
sample cooled to 3° C
• and the average ambient temperature.
The first group in the equation calculates the amp-hours
required to cool the sample liquid as it is collected. The total
sample volume, V c , can be determined by the programmed
number of samples multiplied by the sample volume. If the
D-1