BMW F12 2011 Technical Training Manual page 53

F12￿Chassis￿Dynamics
5.￿Steering
F12￿Charging￿the￿auxiliary￿battery￿in￿24￿V￿mode
Index
1
2
3
4
5
6
7
LIN-Bus
The￿auxiliary￿battery￿can￿be￿charged￿in￿24￿V￿mode￿using￿the￿battery￿charging￿unit.￿The￿charger￿draws
the￿power￿required￿for￿this￿from￿the￿vehicle￿electrical￿system￿via￿the￿Luggage￿compartment￿power￿dis-
tribution￿box.
When￿the￿Electric￿Power￿Steering￿is￿in￿24 V￿mode,￿the￿auxiliary￿battery￿is￿charged￿via￿the￿charging
controller￿for￿auxiliary￿battery￿(BCU).￿As￿a￿voltage￿of￿24￿V￿is￿present￿in￿the￿EPS￿circuit￿due￿to￿the￿series
connection￿of￿the￿main￿and￿auxiliary￿battery,￿the￿auxiliary￿battery￿can￿only￿be￿charged￿using￿a￿special
measure.
This￿involves￿using￿a￿DC/DC￿converter￿in￿the￿charging￿controller￿for￿auxiliary￿battery￿(BCU)￿that￿pro-
duces￿different￿voltages￿at￿the￿input￿and￿output￿that￿are￿isolated￿from￿one￿another.
Energy￿is￿drawn￿from￿the￿vehicle￿electrical￿system￿and￿fed￿to￿the￿auxiliary￿battery.
Explanation
Battery￿power￿distribution￿box
Battery
Intelligent￿battery￿sensor￿(IBS)
Auxiliary￿battery
Separator
Charging￿controller￿for￿auxiliary￿battery￿(Battery￿Charge￿Unit￿[BCU])
Luggage￿compartment￿power￿distribution￿box
Local￿interconnect￿network￿bus
49