Portable Power Module for Güralp Certimus
Appendices
power mode to preserve any remaining charge for as long as possible. If charging
resumes, the PPM will monitor the cells until a terminal voltage of 3.2 V is reached,
at which point the power output will be turned on again.
Note:
To maintain continuous operation of the connected instrument, it is
important that the cell voltage is monitored and the installation planned
so that the cell voltage does not fall below 3 volts.
The Li-ion cells used in the Power Module are connected in “2S” (i.e. “ 2 Series”)
configuration which means that two banks of cells are connected in series, as in the
simplified diagram below. Because of this, the output voltage is twice that of each
individual cell’s terminal voltage.
(There is a third connection, not shown above, to the intermediate contact between
the two sets of cells. This is used to monitor and adjust the balance of charge
between the two banks.)
6.1.2 Temperature issues
It is important to understand the operational limits of Li-ion cells with regard to the
temperature conditions at the intended installation location. Note that the
acceptable temperature ranges for charge and discharge differ.
Discharge of the cells (i.e. the PPM's ability to provide power to an instrument) is
specified over the range -20°C to +60°C. Charging, however, is specified ONLY over
the range 10°C to +45°C.
The PPM monitors its own temperature and controls charging accordingly. Charging
will be restricted or even disabled when the temperature approaches or exceeds the
operational limits. The maximum charging rate is only available when the
temperature is in the range +10°C to +40°C.
The PPM simultaneously limits the charge input current to approximately 8 Amps
and the input power to around 80 Watts. As the cell voltage attains it’s maximum
voltage (4.2V) the charging rate is reduced accordingly. Even if available power is at
a maximum, it cannot allow further charging of the cell for safety reasons.
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Issue A - May 2021
