Xylem SDI-12 Data Logger iRIS 220, iRIS 320, iRIS 350, iRIS 150, iRIS 300 - Manual (Page 15)

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3.5.1 Internal Battery
The iRIS 320 and iRIS 350 are supplied with an internal rechargeable 12V 0.8A/Hr sealed lead-acid battery.
Upon installation, you will need to connect this battery as it is shipped disconnected to preserve battery life. It
should also be disconnected if the unit is not going to be used for some time.
For maximum flexibility, the iRIS I/O connector has two terminals provided for additional 12V power supply
flexibility. These terminals (marked 12V+ and GND) can either be used to deliver 12V from the internal
battery out to power an external sensor or other small load, or alternatively be connected to an external 12V
battery (for greater battery capacity) or a 12Vdc battery charger type power supply. See the next two
sections on using the 12V terminals and the external (charger) power supply feature.
3.5.2 Internal / External 12V Battery Supply
There are two terminals provided on the I/O connector designated +12V and GND (or –12V on early
models). These can be used to power the unit from an external 12V battery or regulated dc supply. The
internal battery is effectively connected directly to these terminals. See Section 3.5.1 above for warnings on
connecting external power supplies to them.
3.5.3 External (Charger) Power Supply
Although the iRIS 320 or iRIS 350 can operate solely from their internal battery for a few days, you will
typically need to connect an external supply to the unit so that the internal battery remains in a charged
state. You can connect any external dc power source ranging from 15 – 30Vdc, including a solar panel,
without requiring an additional solar regulator.
The battery charging circuitry utilises a switch mode regulator for maximum efficiency. The external power
supply is protected against over-voltage by ultra-fast acting protection devices and a self-resetting
semiconductor fuse.
It can also be used to charge an external battery connected to the GND and 12V+ terminals. In the event
that the external battery draws excessive current, the charger will enter a current limit mode (900mA) until
such time as the battery has been recharged sufficiently to deliver the full supply voltage. The charging
profile used by the charger depends on the selected mode. See the Power Management description in
Section 4.4.1.
The battery charger operates in a simple dual mode “float” / “charge” pattern. To do this it
regularly switches between two voltage levels to optimise the battery charge. The actual
profile is determined by the Power Source setting.
When the Power Source is set to “DC”, the battery voltage will rise and fall every two hours
giving a “sawtooth” type voltage plot if the data is logged. This is normal.
WARNING!
INTERNAL BATTERY
The 12V +and GND terminals of the I/O connector are effectively connected directly in parallel with
the internal 12V battery. A resettable semiconductor fuse is fitted for short-circuit protection.
However, only connect 12V lead-acid batteries or a regulated d.c power supply that is designed
for charging a 12V lead-acid battery, to these terminals.
Applying a voltage higher than 14.5V for a sustained period to these terminals will permanently
damage the internal battery and may cause an acid leak and/or an explosion.