Theory of Operation
- 28 - IQ SERIES OWNERS MANUAL
blink. The battery voltage has decayed to 10.5 Vdc (or 21.0 Vdc for 24 volt models). Now, apply shore
power and observe the battery charger operation. The system begins with the Charger-Bulk Light
blinking, indicating bulk charge operation. This supplies a constant current charge output. Connect an
ammeter to the DC cables between the inverter and the battery to monitor the current (DC amps), and a
volt meter to the battery to monitor the battery voltage rising.
After some time, the battery voltage rises to the Absorption voltage (14.4 VDC for wet batteries or 14.1
VDC for gel batteries). The Charger-Bulk light continues to flash, indicating the charger is in Bulk or
Absorption mode. The battery voltage remains constant (Absorption voltage value), and the charger
output current tapers off. After approximately twenty minutes, the charge advances to Float mode. The
Charger Float LED turns ON and the battery voltage drops to the float voltage value (13.2 VDC for wet
batteries or 13.6 VDC for gel batteries). The charger will remain in this stage until shore power is removed
or until the battery will again accept the bulk charge amperage.
5 THEORY OF OPERATION
5.1 Battery Charger Power Consumption
The battery charger will draw approximately 27.5 AC amps from shore power when the 12 volt charging output is
120 amps. A lower charger setting will draw proportionally lower AC input amps. Be careful that the AC input
power required for battery charging combined with the passthrough power required for the AC loads does not
overload the AC source. The optional Remote Automatic Power Management (APM) Panel, Vanner part number
D07934, allows remote adjustment of the maximum AC input amps the charger can draw.
5.2 Battery Charger Operation
The IQ Series' Battery Charger incorporates an automatic, three-stage charger. This design enables the unit to
automatically charge batteries, maintaining the battery's integrity and reducing the likelihood of premature failure.
The battery charger is designed to be used with lead-acid type batteries including sealed and gel types, but not
for nickel-cadmium (Ni-Cad) or nickel-iron types.
There are three automatic charge stages; Bulk, Absorption, and Float.
Bulk Charge Stage
The Bulk Charge Stage (fixed current) provides a fixed charging current for rapid charging of the battery
bank. The charger output current is adjustable in 8-Amp steps (4-Amp steps on 24-Volt systems), up to
the maximum charger rating, to match the charging requirements of the battery. The Bulk Stage is
initiated when the battery will accept the charging amps selected. As the battery accepts charge the
battery voltage will rise to the charger's Bulk Voltage value, 14.4 VDC for flooded batteries, or 14.1 VDC
for gel batteries (on 24-Volt systems 28.8 and 28.2 respectively). When battery voltage reaches the Bulk
Voltage Value the Bulk Charging Stage is complete. At this point, the battery is approximately 80-percent
charged.
Absorption Charge Stage
During Absorption Charge Stage (fixed voltage), the charger's output voltage remains fixed at the Bulk
Charge value and the output current will decrease as the battery becomes fully charged. The Absorption
Stage ends after twenty minutes and the charger advances to the Float Stage.
Float/Maintenance Charge Stage
When the charger enters Float Stage, its output voltage is reduced to the float voltage value 13.2 VDC for
flooded batteries, or 13.6 VDC for gel batteries (on 24-Volt systems 26.4 and 27.2 VDC respectively).
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