Bus Power & Battery Guide

Bus Power & Battery Guide

Overview

This document describes power usage of the Transportant system during its various operational modes along with options for monitoring and management.

Power Draw of Transportant System

The Transportant system connects to a vehicle's constant power. It monitors vehicle ignition status and geofencing to switch to standby or sleep mode to minimize power consumption.

Active Mode

Active mode is the default.  Active mode records video, GPS history, ridership events, and powers the cameras and the driver's copilot. All system functionality is available in active mode. The system moves to active mode in response to any of these events:

  1. The ignition is on
  2. The key is in accessory position
  3. The Switch to Live Stream control is selected on the dashboard while the system is in Standby Mode

Power consumption during active mode has a minimal impact on battery levels because power is available from the alternator. Active mode continues briefly after ignition is off to record post-trip activity for about 10 minutes.

Power consumption during active mode depends on the installed system components and is approximately:

  1. 700 milliamps base power 
  2. 220 milliamps for driver's copilot power
  3. 170 milliamps per camera during daytime
  4. 370 milliamps per camera in darkness using night vision (infrared LEDs are active for night vision)
Dash cameras facing the windshield do not use night vision LEDs regardless of darkness as the infrared would be reflected by the windshield.
For example, a system with 3 cameras and copilot would consume (700mA for cameras)+(220mA for copilot) +(510mA for 3x cameras) = 1.4 amps of power when in active mode during daylight.

Standby Mode (shutdown timer)

During standby mode power usage is reduced as much as possible while still allowing for offloading and viewing of recorded video. All cameras, the driver's copilot, and any ridership accessories are all powered off including RFID reader, barcode scanner, 10 key keyboard input, etc.
The system stays in active mode for about 10 minutes after the ignition turns off. At that point the system will enter standby mode if:
  1. It sees a known parking lot wireless network
  2. The bus is located within the geofence for a point of interest that has video recording turned off
  3. The Switch to Live Stream control has not been selected within the last 10 minutes
Power consumption during standby is approximately 670 milliamps.
Power consumption during standby mode is influenced by the parking lot wireless network because the system adjusts antenna transmission power automatically to reach nearby access points on uncongested channels.  If no wireless network is available the system will rely on cellular uplink which uses more power than Wi-Fi.

Sleep Mode

When the system detects that the ignition is off, it starts a configurable per bus shutdown timer. The default setting is 180 minutes (3 hours.)  If the system detects battery voltage of less than 12.04 volts, the shutdown timer is automatically reduced from its configured setting to a maximum of 20 minutes. The shutdown timer is reset (i.e. starts over) whenever ignition status is detected.
When in sleep mode, all systems are shut down except the onboard clock, ignition monitor, and sleep mode indicator LEDs. The system is not reachable over cellular or Wi-Fi, and GPS location is not monitored or recorded. The system will wake up and switch to active mode the next time the ignition is on.
Power consumption during sleep mode is approximately 70 milliamps.

Dead Mode

Most systems are not installed with physical kill switches.  For systems that are installed with a physical power kill switch, activating the switch puts the system into dead mode.  In dead mode, the system draws no power at all, but the only functionality available is the built-in clock which is powered by a small internal battery. 
In dead mode, the system cannot monitor for ignition and will not exit dead mode until the kill switch is deactivated.  When the kill switch is deactivated and the system has power again it enters sleep mode.  From sleep mode it will become active again the next time ignition power is detected.

Dashboard Battery History Chart

The Transportant system monitors ignition voltage and battery voltage.  These values are recorded and sent to the cloud when the system first enters active mode, when the ignition status changes, and periodically every hour during active mode. You can see the history of recorded ignition and battery data on the battery chart for each bus.  Access this from the Dashboard on the Buses page. Select the bus you are interested in, then select the vertical dots in the top right corner and choose "Battery Chart."


Changes in Batteries in Recent Years

There are two types of automotive batteries that are available, AGM (absorbed glass mat) and flooded (standard liquid filled) batteries. AGM batteries were introduced more recently and have a lifespan of five to seven years, while the flooded batteries have a lifespan of three to five years. 
The AGM batteries are more expensive, but they are less susceptible to vibration and heat. Flooded batteries are more susceptible to heat and vibration, which is the primary environment that they live in on a bus. In the last 5-10 years, battery manufacturers have increased the plate size of batteries to get more cold cranking amps out of a normal size battery. This decreases the amount of space available for electrolysis by-products below the plates. 
AGM batteries are marked AGM and the labels will be a different color depending on make. For example, Optima has red, yellow & blue tops on their AGMs, while Advance Auto AGMs have silver labels.

Difficulty of Battery Testing and Inspection

Batteries on buses are usually in an area that prevents easy inspection and service. Their location exposes them to road grime, corrosion, heat and vibration, all of which are detrimental to the long life of a battery.

Alternator Output vs. Battery Charging

Ideal alternator output is 14.3 to 14.5 VDC, however, the alternator must power all electrical components on the bus, lights, ignition, fans, etc. The age of the drive belt will affect the ability of the alternator to maintain the required output. Some symptoms of a loose or worn drive belt are; squealing noise when the air conditioner is engaged, noticeable dimming of panel lights or headlights when safety lights are engaged or lights varying in brightness depending on the speed of the engine. 

Reducing Battery Usage

Operators can take these steps to reduce battery usage:
  1. Reduce the per bus shutdown timer.  This is a configuration setting for each bus, and is accessible via the dashboard, from the individual bus page.  In the right panel section titled "Vehicle Info" there's an "Edit" link, where the shutdown timer can be changed.
  2. Evaluate and if necessary upgrade parking lot Wi-Fi coverage. Limited Wi-Fi coverage requires each bus to use higher transmission power to reach distant access points.  Without Wi-Fi coverage, buses fall back to cellular transmission which is even more power consuming.

How to Measure Power Usage

To measure the amount of power used by the system requires the use of an amp clamp meter available from Snap-On or Mac Tools. Harbor Freight sells an amp clamp, but the meter must state it reads DC current. Turn on the amp clamp meter, select DC and open the jaws of the clamp and place around the red and yellow wires while the system is energized. The meter will be polarity sensitive, so make sure the meter is showing positive current flow. Record the total current draw of the system for the mode you wish to observe:
  1. For active mode, make sure the system is completely energized. The attendant and copilot should both be on, and the cameras should be recording video. All green port lights on the attendant should be lit in active mode.
  2. For standby mode, make sure that the ignition has been off for at least 20 minutes, and that all green port lights are off (or one light on at a time, rotating quickly through all ports, to indicate sleep mode).  Verify that live video is not available on the dashboard, and that the bus shows as online or stopped (not offline.)
  3. For sleep mode, verify that the bus shows offline, that no green port lights are steadily lit (but may be rotating), and also the yellow aux light is not lit. The system fan should not be audible in sleep mode.

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