hymer BMC 550, Instruction Manual

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8 Electrical system
110
B-MC - 12/18-2 - EHG-0016-01EN
Total discharge of the battery is imminent, if a battery is completely dis-
charged by an active appliance and by closed circuit current and the off-load
voltage falls below 12 V.

Total discharge damages the battery.
Capacity refers to the amount of electricity which can be stored in a battery.
The capacity of a battery is given in ampere hours (Ah). The so-called
K20 value is normally used.
The K20 value indicates how much current a battery is able to dispense over
a time period of 20 hours without causing damage, or how much current is
required to charge a flat battery within 20 hours.
For example, if a battery can dispense 4 amps for 20 hours, then it has a
capacity of 4 A x 20 h = 80 Ah.
If more current flows, the discharging time of the battery will decrease pro-
portionately.
External influences, such as temperature and age may alter the storage ca-
pacity of the battery. Capacity details refer to new batteries operating at
room temperature.

Depending on battery technology, capacity details have a conversion
factor of 1.3 to 1.7, which lowers the real capacity by this value.

A practical example is shown in section 8.3.6.
8.3 12 V power supply

Only connect devices with a maximum of 10 A to the sockets of the 12 V
power supply.
8.3.1 USB and 12 V sockets
Various sockets for operation and charging of electrical appliances are in-
stalled in the vehicle.
Fig. 127 USB and 12 V socket
Through the USB sockets (Fig. 127,1), the batteries of appliances can be
charged with a charging current of up to 2.5 A.
Total discharge
Capacity
USB socket