DOCUMENT NUMBER:
L500-912.820 ISSUE JUL 20, 2016
AMENDMENT: 00
DATE: 
CHAPTERPAGE 339
MAINTENANCE MANUAL STEMME S12
3.7.2 DC GENERATION ATA 243000
3.7.2.1 MAIN SYSTEM DC POWER GENERATION
The DC power for the main system is generated by the belt-driven alternator of the engine and
stored in a LiFePO4 battery.
MAIN SYSTEM BATTERY
Type Super B SB12V19E-EC
STEMME p/n 831.489
Nominal Voltage 12.8 V
Nominal Capacity C1 19.2 Ah
Technology Lithium Iron Phosphate LiFePO4
Protection device Over-voltage protection device OVP-15.5
Qualication Airworthiness and eligibility are proven in /A/
Location Battery case at front ring frame of tail boom
MAIN SYSTEM ALTERNATOR
Type Nippon Denso 42A,
STEMME p/n 830.600
Drive V-Belt
Excitation External, controlled automatically depending on running engine
Field circuit protection 5 A fuse
Nominal Voltage: 14 V
Max Output Power 42 A
Voltage Regulator built-in
Regulated Voltage 14.2 – 14.8V @ 25°C
Qualication The alternator is part of the certied aircraft engine ROTAX 914 series
Location Left side of propeller gear housing of engine
FUNCTION
When aircraft master switch is switched ON the main system master relay connects the battery
to the system. From that moment on all devices supplied by main system are powered, except
those with a dedicated ON/OFF switch. When the engine is running, a pulse train representing
the engine’s rpm is present at the input of a frequency-controlled relay. The relay switches on the
eld circuit of the alternator and the alternator starts to generate voltage. The alternator output
is controlled by a voltage regulator built in the alternator. A red warning light indicates failures
at the alternator, e.g. a broken V-belt.
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