Manual revision 001
Section 2: Description of SBE 39
plus
-IM
SBE 39
plus
-IM
13
Battery Pack Endurance
The SBE 39
plus
-IM battery pack nominal capacity is 5.2 Amp-hours.
For planning purposes, use a conservative value of 4.0 Amp-hours.
The battery pack capacity is achieved if the SBE 39
plus
-IM is deployed in the
recommended orientation: thermistor end down or horizontal.
If
deployed vertically with thermistor end up, battery pack capacity may be
reduced by up to 40%.
See
Deployment Orientation
below for details.
Total power consumption is the sum of:
•
Power required for sampling.
•
Power required for transmitting data.
•
Power required when instrument is awake but not sampling – Each IM
instrument on the mooring draws this current while any of the IM
instruments are being queried to transmit data. Assuming the fastest
practical interrogation scheme (wake all IM instruments on mooring, send
GData
, send
!iiData
to each IM instrument, and power off all IM
instruments, this current is drawn for approximately 1 second
per IM
instrument on the mooring if the 39plus-IM is outputting data in
converted engineering units (OutputFormat=1)
.
•
Quiescent current when asleep.
Battery pack endurance is highly dependent on the application. Examples are
shown below for three sampling schemes. As shown in the samples, for most
sampling schemes, the 39
plus
-IM deployment length will be dependent on the
memory capacity, not the battery capacity.
Notes:
•
If the 39
plus
-IM is logging data and
the battery pack voltage is less than
5 volts for ten consecutive scans,
the 39
plus
-IM halts logging and sets
the logging status to low battery.
•
See Specifications above for
power draws and data storage
limitations.
•
Polled sampling is a very inefficient
use of the 39plus-IM’s battery pack
power; autonomous sampling is
much more efficient, as shown in the
examples below.
•
Power required for transmitting data
and for when instrument is awake
but not sampling (other instruments
on IM line are transmitting data) is a
function of the time required for data
transmission. XML output
(
OutputFormat=2
) has many more
characters than
OutputFormat=1
,
resulting in a large increase in power
consumption.
