Conext XW+ 6848 NA Owner's Manual page 64

Configuration
Float Stage
Two-Stage
3–16
Float charge maintains the batteries slightly above the self discharge voltage of
the batteries. The charge current in float is the current necessary to maintain the
batteries at the Float Voltage setting, limited only by the inverter's capability or
other settings that limit the inverter's maximum charge rate. Float charging
reduces battery gassing, minimizes watering requirements (for flooded
batteries), and helps the batteries remain in a constant state of readiness. When
three-stage charging is selected, the charger automatically switches to the float
stage after the batteries have received a bulk and absorption charge (see Figure
3-4, "Three-Stage Battery Charging Cycle" on page 3–13). The batteries are
maintained at the default float voltage level for the selected battery type or the
voltage selected under Float Voltage on the Custom Battery Settings menu.
Note: The battery voltage can increase above the float voltage when using an
external charging device such as charge controllers attached to PV arrays,
wind turbines, and micro-hydro generators. Be sure to include appropriate
charge management equipment with all external DC sources.
Two-stage (or no float) mode differs from an ordinary three-stage charge mode in
that it does not continuously maintain the battery at float voltage. Instead, the
Conext XW+ begins charging the battery in bulk mode whenever the battery
voltage drops below the recharge level. While the battery voltage is above the
recharge level the inverter's AC transfer switch continues to pass through power
from the utility grid to the loads, but does not actively charge the batteries.
Two-stage mode increases efficiency of utility connected systems by reducing
the amount of power consumed by the inverter and batteries compared to when
the battery is continuously maintained at Float Voltage. This feature can extend
the life of many batteries.
To allow grid support and sell mode to function after battery charging has
completed, it is recommended to set Charge Cycle to 2-stage.
Note: If the AC input stops or drops below the lower VAC limit (as set in
AC Settings), the complete multi-stage charge cycle (bulk, absorption, float/no
float) restarts once the source AC recovers to within the acceptable range. If the
batteries are already nearly full, the charge cycle will take little time to complete.
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