PRINCIPLES OF OPERATION
The Load Manager P is basically a low voltage disconnect which removes power
from the load when the voltage sensed drops below the preset threshold of 11.0
volts for 12VDC operation and 22.0 volts for 24VDC operation. A starter override
is provided to prevent disabling the load while the engine is cranking. This
eliminates re-booting the computer if cranking the engine drops the battery
voltage below the threshold. When the device detects that the engine is not
running a timer is started. After the set time has elapsed the load will be
deenergized. If during the timing cycle, the battery voltage drops below its set
point, the load will be immediately deenergized. Starting the engine at any time
during the timing cycle will reset the timer. A block diagram appears in figure 1.
ENGINE
OFF
SENSOR
TIME
PRE-SET
ADJUST
TRIMMER
TIMER
1 HOUR
TO
2 HOURS
VOLTAGE
PRE-SET
ADJUST
TRIMMER
VOLTAGE
DETECTOR
V
Bat
POWER
RELAY
STARTER
SWITCH “ON”
IF THIS LINE IS
TRUE, THEN THE
POWER RELAY
IS ENERGIZED
V
<
V
IF
TRUE
Bat
Sp
FACTORY ADJUSTED
TO 1 HOUR
AND ENGINE IS “OFF”
T
>
T
IF
TRUE
Sp
TRUE WHILE
ENGINE IS
“CRANKING”
Figure 1
BLOCK DIAGRAM, LOAD MANAGER P
