Master Power Cut-Off and Low Voltage Disconnect
Master Power Cut-off (MPC)
Master Power Cut-off is typically used for cutting all battery power for trucks that are going to be sitting for an
extended period of time, during maintenance, or for use in specialized verticals such as fuel handling. When
the SmartRecorder is connected to a MPC switch it may have a negative impact on the functionality of the
SmartRecorder System.
SmartDrive recommends wiring the SmartRecorder directly to the battery or the HOT side of the MPC Switch.
An MPC Wiring Kit is available from SmartDrive to be used between the battery/ground/MPC switch and the
SR4 Controller.
Part numbers for the SmartDrive Master Power Cut-Off (MPC) Wiring Kit
100-0002-0029-00 Standard Kit Wire Length (15 feet wire length)
100-0002-0030-00 Extended Kit Wire Length (45 feet wire length)
Low Voltage Disconnects (LVDs)
LVD is circuitry that removes “non-critical” loads, such as TVs, radios, and microwaves from the truck battery.
The primary function of LVD is to ensure there is enough battery power left to start and run the vehicle. DO
NOT wire the SmartRecorder through any LVD device as this will negatively affect the normal operation of the
system. If MPC or LVD is not bypassed, the following should be reviewed with the customer prior to
Installation.
1. The SR4 performs self-diagnostics upon Ignition Off that keeps the SR4 in good working order and ensures
maximum uptime. This capability is lost by a master power cut off removing constant power from the SR4
very shortly after ignition off.
2. When wired to constant power and while the ignition is off, the SR4 will continue to process and offload
events that were not able to offload while the vehicle was on the road.
3. When wired to constant power and while the ignition is off, the SmartRecorder 4 is able to receive and
process requests to offload on-demand or Extended Recording events. These offload requests may not
able to be processed should the master power cut-off cause the SR4 not to be powered. Wiring to
constant power maximizes the likelihood that the SR4 will be powered at the time that the request is
made.
4. The SR4™ generates a heartbeat each evening which provides a Health Check that SmartDrive Technical
Support and Customer Service use to monitor and ensure that your SR4 is operating properly. This benefit
would be lost if the SR4 is connected to the switched side of the master power cut-off.
5. Wiring to constant power ensures that the SR4 is able to capture events for parked or unattended
vehicles during the default 1 hour sleep timer after Ignition Off. (e.g., as in the case of roll-a-ways or
mystery damage). The vehicle sleep time may vary, contact SmartDrive for actual timer settings.
6. Privacy mode may not function as designed if wired as part of LVD. The system may restart after an LVD
power loss where it would no longer be in Privacy Mode OR the system’s ignition reference may toggle
removing Privacy Mode.
7. When wired to the switched side of the master power cut-off, or LVD, the SR4 rechargeable battery
experiences a significantly larger number of charging/discharging cycles, which significantly reduces the
usable life of the battery.
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