DOCUMENT NUMBER:
L500-912.820 ISSUE JUL 20, 2016
AMENDMENT: 00
DATE: 
CHAPTERPAGE 340
MAINTENANCE MANUAL STEMME S12
3.7.2.2 ENGINE SYSTEM DC POWER GENERATION
The DC power for the engine system is generated by the crankshaft-mounted generator of the
engine and stored in a LiFePO4 battery. The battery is used to crank the engine to start.
ENGINE SYSTEM BATTERY
Type Super B SB12V7800P-CC
STEMME p/n 831.488
Nominal Voltage 13.2 V
Nominal Capacity C1 7.8 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
ENGINE SYSTEM INTERNAL GENERATOR
Type ROTAX (Part of engine)
STEMME p/n n/a
Drive crankshaft, directly mounted
Excitation permanent magnet
Nominal Voltage 14 V
Max Output Power 18 A
Voltage Regulator external rectier-regulator (ROTAX)
Regulated Voltage 13.7 – 14.3 V
Qualication The generator is part of the certied air raft engine ROTAX 914 series
Locations Coils and magnets mounted on aft end of crankshaft housing,
voltage regulator installed on TCU-Starter-Board.
FUNCTION
If aircraft master switch is switched ON and the aircraft nose cone is opened and locked, a micro
switch at the nose cone lever activates the engine system master relay. The relay connects the
battery to the engine system. The TCU and the main fuel pump operate immediately. Pushing the
ignition-starter key to START activates the starter relay and connects the battery to the starter.
When the engine is running the rotating magnets generate voltage in the generator coils. The
regulator limits the output voltage. A yellow warning light indicates failures of the generator system.
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