Dometic BUTTNER MT BCB25/20, Installation And Operating Manual

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Battery charging function
A main charging cycle of the house battery is initi-
ated in the following situations:
• After a standstill of the alternator or mains failure
• After falling below the reset voltage of 12.75 V
for lead batteries or 13.10 V for LiFePO4 batter-
ies for 30 s
I
The charging characteristics for automated, con-
tinuous operation without monitoring are referred
to as modified IU0U characteristics (see charging
curve in fig.
6
, page 5).
1: Analysis phase
The battery is deeply discharged (>10 %). The bat-
tery charge is analyzed with increasing charging
current.
2: I phase (Constant current phase)
At the beginning of the charging process, the
empty battery is constantly charged with the maxi-
mum charging current (100 %). The charging cur-
rent decreases when the battery has reached a
state of charge of 75 % (90 % for LiFePO4 batter-
ies). Batteries with a voltage of 0 V are charged
with reduced charging current until the battery
voltage exceeds 9 V.
The duration of the I phase depends on the state of
the battery, the load from the consumers and the
state of charge. For safety reasons the I phase is ter-
minated after a maximum of 15 h (in case of battery
cell defects or similar).
3: U1 phase (Constant voltage phase)
The U1 phase starts when the battery is fully
loaded. The charging current is reduced. During
the U1 phase, the battery voltage is kept constant
at a high level. The duration of the U1 phase
depends on the battery type and the depth of dis-
charge.
4: U2 phase (Trickle charging)
The U2 phase serves to maintain the battery capac-
ity (100 %).The U2 phase runs at lowered charging
voltage and variable current. If DC loads are con-
nected, they are powered by the device. Only if
the power required exceeds the capacity of the
device is this surplus power provided by the bat-
tery. The battery is then discharged until the device
re-enters the I phase and charges the battery.The
U2 phase is limited to between 24 and 48 h
depending on the battery type.
5: U3 phase (Storage charging)
In long-term mains operation, the U3 phase pre-
vents further discharge of the battery (e.g. during
long breaks in use, seasonal operation or during
winter storage), minimizes battery gassing and
prevents plate corrosion.
Main Charging
(yellow) On Charging process
in I/U1 phase
Flashing • Over voltage
protection
• Only LiFePO4
batteries: Tem-
perature sensor
is not connected
Batt. II
(yellow) On Booster charging
mode; starting bat-
tery charges the
house battery
Off Booster charging
not activated
Power
(green) On Voltage present;
mains or booster
charging mode
Flashing slowly Safety shutdown
(chapter “Trouble-
shooting” on
page 24)
Flashing in 20 s
interval Pulsing operation
mode
NOTE
In all charging phases (U1 phase to
U3 phase), almost the entire possible
charging current is available for the addi-
tional supply of DC loads without dis-
charging the battery.
LED Status Description