littelfuse if 173 48514 lvd instruction guide
SureStart™ Compact Magnum
Low Voltage Disconnect Switch
LVD & Harness
Programmable LVD
Programmable LVD & Harness
12V/24V DC
250A at 85°C
• If you want to use the alarm feature, Connect Pin 3
Under normal operating conditions this device may run
hot. Please use caution when handling. We recommend
mounting away from direct heat sources, and where
there is air circulation.
Note: All connections to pins 1-4 should be made
using a 12804 harness connector or a Deutsch DT06-4S
“Alarm” to a audio/visual alarm (voltage rating
appropriate for your system) or a relay that draws
less than 250mA. Connect the other side of the
alarm device to Ground.
• If you want to use the ignition countdown
timer feature, connect Pin 4 “IGN” to the ignition
switch (usually to the run position).
Required Connections:
1. Disconnect the battery or power supply or switch
it off using the master disconnect switch before
installation. Please note that connections to pins
should be made with the connector.
2. Connect Pin 1 to ground.
3. Connect Low Voltage Disconnect (LVD) “Load+” stud
to accessory loads using appropriate heavy gauge
Optional Connections:
• If you want to use the manual feature, connect pin 2
“Manual Override” to a center common post of a SPDT
(On - Off - Mom. On) switch. Conect the side that is active
in the Mom. On position to battery voltage. Attach the side
that is active in the stable On to the ground.
• Unused locations in the connector must be filled
with plugs provided.
5. Connect LVD “Battery+” stud to the battery
positive terminal (or battery positive terminal block)
using appropriate heavy gauge cable and proper
NOTE: If a master disconnect switch is used,
the LVD should be installed “after” the master
disconnect, such that the master disconnect switch
can be used to shut off power to the LVD.
6. Reconnect the battery or power supply
Littelfuse Commercial Vehicle Products
IF. 173 Rev A
Normal Operation Summary
Additional Operating Details
• When the unit is powered up it goes into autodetect mode and determines if it is in a 12V or 24V
system and sets the parameters for operation.
• When the voltage is above 13.0V/26.0V for 10
seconds, the LVD will automatically connect the
loads to the battery.
• When the voltage drops below 12.1/24.2V for 60
seconds, the alarm will pulse, warning the user that
the loads are about to be disconnected.
• The user has the option to override the imminent
disconnect by applying battery voltage to the Manual pin.
• After 60 seconds of the alarm, the loads will be
disconnected, and the alarm silenced.
• The alarm can be audio, visual or both.
• Connecting the manual pin to ground will force the
unit to stay shut down no matter what the battery
voltage is.
• The 48514/48714 also has an optional key off
timer disconnect feature. For this feature to work,
the ignition pin of the 48514/48714 (pin 4) must
be connected to a keyed ignition source. If it is
connected and the ignition key is switched off while
the LVD’s output is on, the 48514/48714 starts a 15
minute timer. If the battery voltage remains above
the disconnect threshold while the timer is active,
the output will remain on for 15 minutes and then
disconnect the load. If the battery voltage should
drop below the disconnect threshold for one minute
before the timer expires, the alarm will sound for
one minute and then disconnect the load. If ignition
terminal is connected and the battery voltage drops
below the disconnect threshold for one minute while
the key is on, the loads will not disconnect, but the
alarm will pulse.
Under/Over Voltage
If the voltage falls below the low cut off value
(7V/16V) or above the overvoltage cut out value
(18V/36V) the unit will disconnect the loads until
the voltage returns to the acceptable range. If the
device is out of voltage range the Manual feature is
Connection Check
Upon power-up, the LVD initially checks to ensure
proper cabling, specifically the Battery+ and Load
connections. If improper cabling is detected, the
LVD will activate the alarm on continuously (no
pulse) until the user corrects the cabling. If the load
energizes immediately when Battery+ is connected
and stays on no matter the voltage or the position
of the manual switch, check the B+ and Load
connections to make sure they are connected to
the correct terminals.
Manual Override
When the user uses a switch to connect the Manual pin (pin 2) to battery voltage for 1 second. It forces the unit to stay connected for 15 minutes and then it returns to automatic mode (Alarm snooze).
Overcurrent Shutoff
When the output current exceeds the preset
threshold for 3 seconds, the loads are
disconnected and the alarm is activated. A reset
can be accomplished by connecting the manual
pin to battery voltage (manual override). If a switch
is not used, similar to a Type II circuit breaker,
power must physically be removed from the unit
(at the Battery, at the 48514/48714 battery terminal
or by master disconnect switch) to reset the unit
and begin operating. Investigate and eliminate
the cause of the overcurrent as repeated extreme
overcurrent may damage the unit.
Littelfuse Commercial Vehicle Products
IF. 173 Rev A
Secondary Parts:
General Specifications
• 12804 Compact LVD Harness Assembly
Deutsch DT06-4S Connector
0462-201-16141 Terminal
W4S Wedge
Environmental: -40°C to 85°C. SAE J1455 & J1113
• 58326-06 Rocker Switch
250A @ 85°C
Operating Voltage 9-32V
1mA max quiescent current
Factory Standard Settings:
12V - Less than 12.1V for 2 minutes
24V - Less than 24.2V for 2 minutes
Accuracy ±100mV
12V - More than 13.0V for 10 seconds
24V - More than 26.0V for 10 seconds
Factory programmable.
Accuracy ±100mV
Active High, 250mA
See operating details for alarm conditions
See drawing below. Dimensions are in
inches [mm]
• 55088 Toggle Switch
Littelfuse Commercial Vehicle Products
IF. 173 Rev A
MEGA® fuse
for timer)
alarm LED
Pin 1
Pin 3
Pin 2
Pin 4
SPDT On-Off-(On)
Switch such as Cole
Hersee 55088 or
Please consult the factory if you need further assistance
8am - 4pm Eastern Time
Littelfuse Commercial Vehicle Products
IF. 173 Rev A
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