Alpha Technologies AlphaCell OPzS - Manual (Page 24)

OPzS-BATTERY 24
11.0 Operation, continued
11.1 Battery charging and operation mode, continued
11.1.3 Switch mode operation
In the switch mode operation the battery is separated from the load. Towards the
end of charging the charge voltage of the battery is 2.6 - 2.70 V/cell. The charging
process must be monitored. On reaching a full charge state, charging should be
terminated or switched to fl oat operation mode.
11.1.4 Battery charge/discharge operation
In the charge/discharge operation only the battery supplies operation load. Towards
the end of charging, the charge voltage of the battery is 2.6 - 2.70 V/ cell. The
charging process must be monitored. On reaching a full charge state charging should
be terminated. The battery may be connected to the load if required.
11.2 Hydrometer Readings - Specifi c Gravity
Specifi c gravity is a measurement of the density or weight of the electrolyte compared with
water (1.000). Specifi c gravity decreases on discharge and rises again on charge as a result
of the electrochemical reaction within the cell.
Because both the cell temperature and the electrolyte level affect the specifi c gravity reading,
they should be recorded at the same time as the gravity reading.
Do not take gravity readings immediately after adding water to the cells. Complete mixing
usually takes several days. Because of the low charging currents in fl oat service mixing of the
electrolyte is a very slow process.
When taking hydrometer readings, hold the hydrometer stem in an upright position so that the
hydrometer fl oats freely and does not touch at either the top or the sides.
Periodically clean the hydrometer barrel and fl oat with soap and water for ease of reading
and improved accuracy.
Specifi c gravity readings should be corrected for temperature. For every 10 °C of temperature
above 25 °C, add 0.007 g/cm3 to the hydrometer reading. For every 10 °C of temperature
below 25 °C, subtract one 0.007 g/cm3 from the hydrometer reading.
11.3 Equalizing Charge
Under normal conditions an equalizing charge is not required. An equalizing charge is a
special charge given to a battery when non-uniformity in voltage has developed between
cells. It is given to restore all cells to a fully charged condition.
Non-uniformity of cells may result from:
Low fl oat voltage due to improper adjustment of the charger.
A panel voltmeter that reads high, resulting in a low charger output voltage.
Selection of a low fl oat voltage.
Variations in cell temperatures in the series at a given time, due to environmental
conditions or module arrangement. The maximum cell-to-cell temperature difference is
3°C. If cell temperature is the problem, review the location instructions in Section 5.0 to
ensure proper location of the battery system. •
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