TM-9-2350-311-20-1
HOWITZER, MEDIUM, SELF-PROPELLED, 155MM; M109A2, M109A3, M109A4 AND M109A5
TECHNICAL MANUAL; UNIT MAINTENANCE MANUAL FOR HULL, POWERPLANT, DRIVE CONTROLS, TRACKS, SUSPENSION, AND ASSOCIATED COMPONENTS
AUGUST 1994
TM-9-2350-311-20-1 - Page 40 of 1275
1-17 EQUIPMENT OPERATION AND DESCRIPTION — CONTINUED
1-17.6 Electrical System
The M109A2/M109A3/M109A4/Ml109A5 Howitzers’ electrical system consists of:
a.
b.
c.
d.
e.
f.
g.
Batteries (1) — four 12-V connected in series and parallel to deliver 24 Vdc (nominal) to the master relay (2).
Master relay (2) — delivers electrical power (24 Vdc [nominal]) to operating systems when the MASTER switch
(3) is on. The master relay delivers power directly to the slip ring contact board (TM 9-2350-311-20-2), engine
starter (4), slave start receptacle (5) (M109A3 shown), circuit breaker board (6) (M109A2/M109A3 shown), and
cab (slip ring segment board) (TM 9-2350-31 1-20-2).
MASTER switch (3) — when activated, draws 24 Vdc (nominal) from the battery through the master relay (2) to
operate the M109A2/M109A3/M109A4/M109A5 Howitzers’ electrical systems. With the MASTER switch ON,
systems can be operated without running the engine.
Alternator (7) — engine driven and delivers 24 Vac (nominal) to the rectifier (8).
Rectifier (8) — full-wave, bridge rectifier converts the generator ac voltage to dc voltage which is in turn
delivered to the voltage regulator (9).
Voltage regulator (9) — controls the delivery of 24 Vdc (nominal) to the vehicle operating systems through the
master relay (2) and also acts as a recharger for the batteries when the engine is operating.
External power receptacle (10) — provides vehicle auxiliary power from an external source.
1-26
TM 9-2350-311-20-1
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