Application & Installation Guide
Starting Systems Application and Installation Guide
©2016 Caterpillar
All rights reserved. Page 7
generator sets are subject to long idle periods or many short stop-start
cycles, insufficient battery capacity could threaten dependability.
Optimum charging volts for 12-volt battery vs. temperature for lead acid
batteries, utilizing a charger.
*Use Caterpillar Data Sheet, PEHJ-0073 to identify chemical construction of Caterpillar
batteries to determine recommended charging voltages in previous table.
Charging Systems
Normally, engine-driven alternators are used for battery charging. When
selecting an alternator, consideration should be given to the current draw of
the electrical accessories to be used and to the conditions in which the
alternator will
be operating. An alternator must be chosen that has adequate capacity to
power the accessories and charge the battery. If the alternator will be
operating in a dusty, dirty environment, a heavy-duty alternator should be
selected.
Consideration should also be given to the speed at which the engine will
operate most of the time. An alternator drive ratio should be selected so
that the alternator is capable of charging the system over the entire engine
speed range.
Engine-driven alternators have the disadvantage of charging batteries
only while the engine is running. Trickle chargers are available but require
an A/C power source. Battery chargers using AC power sources must be
capable of limiting peak currents during the cranking cycle or must have a
relay to disconnect the battery charger during the cranking cycle. In
applications where an engine-driven alternator and a battery trickle charger
are both used, the disconnect relay must be controlled to disconnect the
trickle charger during cranking and running periods of the engine.
Note: Marine and Petroleum engines use separate ground starters and
alternators. See section for further information.
Starter Motor
Continuous Cranking Time Limit with Electric Starter Motors
To avoid overheating of the starter motors, an engine should not be
cranked continuously for more than 30 seconds.
Temp
C
Temp
F
MF
CA/CA
MF
CA/CA
SB
SB
Low
SB
Hybrid
Low
SB
Hybrid
AGM
AGM
GEL
GEL
Min
Volts
Max
Volts
Min
Volts
Max
Volts
Min
Volts
Max
Volts
Min
Volts
Max
Volts
Min
Volts
Max
Volts
80
176
12.90
14.70
12.60
13.20
12.60
13.80
12.90
13.50
12.80
12.90
60
140
12.94
14.74
12.64
13.24
12.64
13.84
12.90
13.54
12.80
12.94
40
104
13.32
15.12
13.02
13.62
13.02
14.22
13.02
13.92
13.02
13.32
20
68
13.80
15.60
13.50
14.10
13.50
14.70
13.50
14.40
13.50
13.80
0
32
14.46
16.26
14.16
14.76
14.16
15.36
14.16
15.06
14.16
14.46
-30
-22
15.90
17.70
15.60
16.20
15.60
16.80
15.60
16.50
15.60
15.90