Dometic Buttner MTBCB10 Installation And Operating Manual page 17

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
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.
The charging characteristics for fully automated
continuous 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
battery 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 DC loads and the state of charge. For safety
reasons the I phase is terminated 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.
6: Reconditioning
Twice a week, the charger switches back to the
U1 phase for a short time (max. 1 h) in order to
revive the battery. This prevents any fatigue phe-
nomena such as sulfation or electrolyte stratifica-
tion.
Temperature sensor
With the temperature sensor connected, the bat-
tery control booster adjusts the charging voltage
(for lead batteries) or the charging current (for LiFe-
PO4 batteries) according to the measured tem-
perature at the battery.
I
NOTE
• For lead batteries: Without tempera-
• For LiFePO4 batteries: Without tem-
The charging characteristics are adjusted as fol-
lows:
• For lead acid batteries see fig. 7, page 5
• For AGM batteries see fig. 8, page 5
• For lead gel batteries see fig. 9, page 5
• For LiFePO4 batteries see fig. 0, page 5
4445103620
ture sensor connected, the charging
voltage is referenced to 20 °C.
perature sensor connected, the bat-
tery control booster does not work.
17