Xantrex Technology 10 - Manual (Page 50)

Operation
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Battery Charging
Completely recharging wet cell deep-cycle batteries requires that the battery
voltage be raised beyond what is known as the gassing point. This is the voltage at
which the battery begins to bubble and gas is given off. If charging stops short of
this point, sulfate is left on the plates and deterioration of the battery begins. The
gassing point will vary with battery temperature. At 25 degrees C, the gassing
point of a 12-volt battery is about 14.0 volts. Battery charging without excessive
gassing of the batteries is accomplished with three-stage chargers. This technique
is used in the Freedom 10.
Gel cell batteries must not be charged to their gassing point. In fact high voltage
charging that gasses these batteries is harmful to them. These batteries do not give
off water vapor. The float voltage can be higher than that of wet cell batteries.
Conventional Battery Chargers
Most conventional battery chargers are single stage constant voltage chargers. As
such they must stop short of the gassing point or they will overcharge the battery
bank. Therefore, most 12-volt battery chargers bring the battery voltage up to
about 13.8 volts.
There are two problems with this. First, since the battery voltage does not reach
the gassing point, sulfate is left on the plates. Second, 13.8 volts is close enough to
the gassing point that some gas will escape, and the battery will need to be
frequently topped up with distilled water.
Conventional battery chargers also suffer from another inherent characteristic of
their design, which is a tapering output. While they will deliver their rated current
into a deeply discharged battery, as the battery becomes charged and the voltage
rises, the output current of the charger tapers down. This taper continues as the
battery is charged, taking a very long time to reach an acceptable recharge.
The Freedom Battery Charger
The Freedom battery chargers are designed to overcome the limitations of
conventional chargers by utilizing three distinct stages, each designed for optimal
recharging of both wet cell and gel cell deep-cycle batteries.
Each time the battery charger is engaged, the three stages proceed automatically,
resulting in an efficient, complete recharge and safe battery maintenance. In
addition, use of the remote control provides the ability to periodically apply an
8-hour timed equalizing charge.
Important: The Freedom 10 Battery Charger is on whenever there is AC power
connected to the charger input, regardless of the condition of the ON / OFF switch.