UMAX090600 Version 1
Preliminary Documentation – May be Subject to Change
6-48
Voltage, Current
Constant Constant
current current
Constant
voltage
Constant
voltage
Voltage
Current
Time
Precharge
stage
Bulk Charge stage
Absorption
stage
Float stage
Maintaining
Charging
Charge
1.2.
Battery Charge Function Block
The CAN-BC-LED implements a 3-stage charging algorithm profile with a separate
Maintaining
Charge
stage. The three stages are pre-charge, bulk and absorption. The
Maintaining Charge
stage is also referred to as float stage.
1.2.1.
Battery Charger Operation
Figure 1 provides a visual description of the charging process the battery undergoes using the
CAN-BC-LED controller.
Figure 1: Three-stage Charge Profile with Float Stage
The charging process begins from the Pre-charge Stage, then, when the battery voltage reaches a
certain point, the charger switches to the Bulk Charge Stage, and, finally, the charging process is
finalized in the Absorption Stage.
After the battery is fully charged, the charger maintains the battery charge in the Float Stage.
1.2.2.
Pre-charge Stage
This is the stage from which the charging operation begins. The controller is continuously
monitoring the battery voltage. If the battery voltage is low, the controller will shift to this stage and
begin charging the battery slowly at a low constant current level. A low constant current level is
used to prevent damage to the battery when it is deeply discharged. Otherwise, providing a high
constant current level could cause gas emission from the battery electrolyte and potentially
damaging the battery. The pre-charge constant current level will remain engaged until the battery
voltage has increased to a certain threshold that is safe for the battery to begin bulk charge.
