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Xantrex RV Series Inverter/Charger Owner’s Manual
7
• Temperature Compensation: The optimum voltage is temperature dependent. As
temperature decreases the proper voltage for each charge stage needs to be increased. The
optional temperature probe will automatically rescale charge voltage settings for ambient
temperature. The compensation slope based on cell voltage is -2.17 mV per degree F per
cell.
Charger Terminology
• Bulk Voltage: This is the maximum voltage at which the batteries will be charged during a
normal charging cycle. The normal range is 2.367 to 2.4 volts per cell. For a 12 VDC battery
(6 cells) this is 14.1 volts for gel cell type batteries and 14.4 volts for lead acid batteries.
• Float Voltage: This is the voltage at which the batteries will be maintained after they have
been charged. In 12-volt systems 13.4 volts for gel cell batteries and 13.5 volts for lead acid
batteries will be maintained by the charger.
• Absorption Stage: During this part of the charge cycle, the batteries are held at the bulk
voltage and accept whatever current is required to maintain this voltage.
• Battery Temperature Compensation: When installed this adjusts the bulk and float voltages
depending on the battery temperature. As battery temperature increases the voltages are
reduced, and as temperature decreases the voltages are increased. This is highly
recommended for sealed batteries.
Three Stage Battery Charging
The battery charger in standby models normally charges in three stages—bulk, absorption and
float—to provide rapid and complete charge cycles without undue battery gassing.
Stage One: Constant Current/Bulk Charge
This stage is initiated when AC is applied to the AC input of the inverter.
Stage one charges the batteries at a constant current. The level of charge for this phase is set
using the BATTERY CHARGER RATE control on the front panel. The constant current phase is
terminated when the batteries reach the bulk charge voltage. During this stage the Charger LED
glows orange.
Stage Two: Constant Voltage/Absorption
Absorption is initiated when the Bulk Voltage setting has been reached. At this point the charge
current begins to taper off at whatever rate is required to hold the voltage constant. During this
stage the Charger LED blinks orange. The absorption phase is terminated in one of two ways.
1. Normally, as the charge cycle progresses, the current required to hold the battery voltage
constant gradually reduces. When this current equals the programmed return amps setting,
the voltage is allowed to fall to the FLOAT (float voltage) setting—stage three.
2. If there are DC loads on the batteries, the current may never fall to a level low enough to
initiate the float voltage stage. A timer is used to ensure that the battery voltage does not
remain indefinitely at the bulk charge voltage. The timing circuit terminates stage two if the
charge current does not reach the return amps value setting within 12 hours.