UMAX090690. Version: 1.2 Preliminary Documentation
– May Be Subject To Change
7-37
2. BATTERY CHARGER THEORY OF OPERATION
The battery charger implements a three-stage charging algorithm with an additional charge stage
for maintenance.
Constant
voltage
Voltage
Time
Precharge
Stage
Bulk Charge Stage
Absorption
Stage
Float Stage
Current
Constant
current
Constant
current
Constant
voltage
Voltage, Current
Charging
Maintaining
Charge
Figure 1. Battery Charger Algorithm Profile
The charging process starts from the Precharge Stage, then, when the battery voltage reaches a
certain point, the charger switches to the Bulk Charge Stage, and the charging process is finalized
in the Absorption (Constant Voltage Charge) Stage.
After the battery is fully charged, the charger maintains the battery charge in Float Mode.
2.1.
Battery Charger Modes
Each stage of the charging process corresponds to one or two battery charger modes. There are
also modes reflecting an idle or an error condition of the charger and a special power supply mode
used for testing.
The charger starts functioning from Idle Mode. It stays in Idle Mode until the Charger is enabled,
and a battery is connected to the charger.
Ich
Ibc
Vbc_start
Vbat
Vpc_start
Vbc_rst Vfl_start
Vfl
Vcv_start
Vcv
Veq_stop
Ipc
Ieq
Icv_stop
Ifl_stop
Figure 2
. Voltage-Current Charging Profile
