Cirrus SR20 Maintenance Manual page 20

C I R R U S
A I R P L A N E M A I N T E N A N C E M A N U A L
turned on, the ammeter indicates the charging rate applied to battery 1. Due to the inability of the alter-
nators to dissipate current, the alternator ammeter indications are positive only.
Serials 1582 & subs: Main and Essential Bus voltages are displayed on the MFD and PFD, therefore,
no ammeter select switch is necessary.
N. Turn Coordinator Batteries - Serials 1005 thru 1267
Turn coordinator batteries provide emergency power to the turn coordinator in the event of essential
power bus failure. Turn coordinator batteries consist of three date stamped 9-VDC Duracell MN1604
batteries connected in series to provide 27-VDC to the turn coordinator and the stall warning horn.
When the turn coordinator battery switch is manually selected the turn coordinator batteries will pro-
vide at least 30 minutes of power for the turn coordinator. When replacement is required, replace all
turn coordinator batteries at the same time, ensure expiration dates are the same, and expiration date
is valid through the next annual inspection date.
Turn coordinator batteries are independently controlled and wired to the turn coordinator and stall
warning horn power source allowing it to function properly when connected with battery 1 and the
alternator. Failure of the battery 1 will not affect the ability of the turn coordinator batteries to provide
necessary power. Because of diode protection, a failure or malfunction of the turn coordinator batteries
will not affect Battery 1 or the alternator.
O. Battery 1 (See Figure 24-3013)
Serials w/ TCM Battery: Battery 1 is a 24-volt, 12-cell, 10-ampere hour, lead-acid aviation-grade type
battery with non-spill vent caps. The battery is mounted in the engine compartment and has a top vent
with an acid-resistant tube. The tube discharges out the bottom of the engine cowling, preventing the
build up of dangerous or explosive gasses within the engine cowl.
Serials w/ Concorde Battery: Battery 1 is a 24-volt, valve regulated, lead-acid aviation-grade type bat-
tery. The battery is mounted in the engine compartment.
Serials 1268 & subs: Battery 1 is used for engine starting and can also be used as an emergency
power source in the event Battery 2 or either alternator fails. Battery 1 provides all the electrical power
for starting the aircraft. Battery 1 also supplies the electrical power to the landing light in the event
Alternator 1 fails. Battery 1 is independently controlled by the BAT 1 switch, located in the pilot's bolster
panel. The BAT 1 switch energizes a relay in the MCU which will connect BAT 1 to the Main Distribution
Bus.
P. Battery 2 - Serials 1268 & subs
Battery 2 is a maintenance free rechargeable sealed lead acid battery. Battery 2 consists of two 12-
volt, 6-cell, 7-amp-hour batteries connected in series to provide 24-VDC to the Essential Bus. There is
no need to check the specific gravity of the electrolyte or add water to these batteries during their ser-
vice life.
Battery 2 is independently controlled by using the BAT 2 switch, located in the pilot's bolster panel. The
BAT 2 switch energizes a relay located just aft of bulkhead 222 in the MCU which will connect BAT 2 to
the Essential Bus. The electrical power from BAT 2 reaches the Essential Bus through the circuit
breaker panel. Battery 2 is mounted directly behind bulkhead 222 in an acid resistant battery container.
Battery 2 is primarily used to power the Essential Bus. The Essential Bus delivers electrical power to
the annunciator lights, turn coordinator, attitude indicator, horizontal situation indicator (HSI), stall
warning system, and alternator 2.
Failure of the BAT 1 will not affect the ability of BAT 2 to provide necessary power to the Essential Bus.
Because of diode protection, a failure or malfunction of the BAT 1 will not affect BAT 2 or either alterna-
tor output.
24-30
Page 20
15 Dec 2014
(See Figure 24-3012)
(See Figure 24-3014)
EFFECTIVITY:
All
M O D E L S R 2 0