Auxiliary Power System - JLG 1200SJP Service Maintenance Manual

SECTION 3 - CHASSIS & TURNTABLE

3.24 AUXILIARY POWER SYSTEM

The auxiliary power system is intended as a secondary means
of moving the boom in the event of primary power loss. This
system uses an electric motor/pump unit powered by a 12V
battery capable of operating all functions except drive, con-
trolled arc, controlled boom angle, and envelope tracking.
During lift up or down functions, no other functions are per-
mitted and during lift up functions, automatic platform level-
ing is not active. To reduce the demand on the battery and
therefore extend the run time of the system, the auxiliary
power functionality differs from the primary power functional-
3-114
ity. The auxiliary power lift down function supplies pilot pres-
sure to the lift cylinder allowing gravity to lower the boom.
The system redirects discharge oil from the lift cylinder to
retract the telescope cylinder. When the boom is retracted to
the transport length, the telescope in valve is dropped out and
lift down is operated alone allowing the platform to reach the
ground. This not only greatly reduces the power required for
these functions but also lowers the boom within the envelope
regardless of starting position. Envelope control and moment
control remain active during the auxiliary power function.
1. Auxiliary Pump
2. Power Relay
3. Battery
Figure 3-64. Auxiliary Pump Installation
– JLG Lift – 3121142