Enabling Asset Security & Management BPS.0707.01P Batteries and Power Supplies.
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Transcript of Enabling Asset Security & Management BPS.0707.01P Batteries and Power Supplies.
Enabling Asset Security & ManagementBPS.0707.01P
Batteries and Power SuppliesBatteries and Power Supplies
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Powering Your ApplicationPowering Your Application
Can be a complex decision Many factors to be
considered Technical Commercial Operational Support
The success or failure of your application can be affected
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Power SuppliesPower Supplies
Available sources of power AC source Batteries Vehicle switched or unswitched? Solar cell Standby requirements Multiple sources
Operating modes Differences between normal & standby
operation
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GuidelinesGuidelines
Optimize for low power operation Exception based reporting Power GPS on demand
Geofencing & distance based scripts require the DMR to be constantly receiving GPS positions
Sleep modes Minimize receive periods to minimize power
consumption
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Power ConsumptionPower Consumption
DMR-200 power consumption Receiving 0.8 W
Idle 0.25 W GPS 1.2 W Transmitting 10.2 W Heater (activated at -25°C) 2.8 W Sleep (@ 12 V) .005 W
I/O power consumption Displays, keyboards, etc. Sensors, actuators, etc.
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Typical Power ConsumptionTypical Power Consumption
Normal Operation ~ 1 Watt (~2 Ah/day @ 12V)
GPS push to fix ~ 0.5 Watts (~1 Ah/day @ 12V)
Low Power (no listen) 1 hour reporting~ 0.1 Watts ( ~0.2 Ah/day @ 12V) 4 hour reporting~ 0.03 Watts ( ~0.05 Ah/day @ 12V) 8 hour reporting~ 0.02 Watts ( ~0.03 Ah/day @ 12V) 1 / day reporting ~ 0.01 Watts ( ~0.02 Ah/day @ 12V)
Low Power (10 minute listen) 1 hour reporting~ 0.2 Watts ( ~0.3 Ah/day @ 12V) 4 hour reporting~ 0.04 Watts ( ~0.1 Ah/day @ 12V) 8 hour reporting~ 0.03 Watts ( ~0.05 Ah/day @ 12V) 1 / day reporting ~ 0.01 Watts ( ~0.03 Ah/day @ 12V)
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Calculating Power ConsumptionCalculating Power Consumption
Determine sequences of operation for the DMR-200 terminal # of terminal originated messages a day? When can terminal receive a message? How long will terminal be in sleep mode? Will terminal be in -25°C environment? Will digital open collector output be used?
Calculate power consumption for operating period
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ExampleExample
Transmit 1 message per day Listen for 10 minutes after each
transmission Shutdown the rest of the time Sequences
Acquire bulletin board Acquire GPS Acquire traffic channel Monitor bulletin board Transmit Listen for 5 frames Sleep
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Power Calculation – 1 Tx Per DayPower Calculation – 1 Tx Per Day
Time (seconds) Power (Watts) Energy (Joules)
Acquire bulletin board 140 0.9 126
Acquire GPS 60 0.5 30
Acquire traffic channel 24 0.9 22
Monitor bulletin board 60 0.9 54
Transmit 8 10 80
Listen for 5 frames 120 0.9 108
Idle 530 0.25 133
Sleep 85458 0.006 513
Total 86400 0.012 1065
Average current @ 12V (Amps) 0.001
Amp hours per day 0.025
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Power Calculation – 2 Tx Per DayPower Calculation – 2 Tx Per Day
Time (seconds) Power (Watts) Energy (Joules)
Acquire bulletin board 140 0.9 126
Acquire GPS 60 0.5 30
Acquire traffic channel 24 0.9 22
Monitor bulletin board 60 0.9 54
Transmit 8 10 80
Listen for 5 frames 120 0.9 108
Idle 530 0.25 133
Additional transmit cycle 942 0.586 552
Sleep 84516 0.006 507
Total 86400 0.019 1611
Average current @ 12V (Amps) 0.002
Amp hours per day 0.037
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Battery Technology SelectionBattery Technology Selection
Primary - non rechargeable Secondary - rechargeable Considerations
Service life Operating mode Frequency of reporting Operating environment
Temperature range Available power sources
Charge requirements
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Primary Batteries - Primary Batteries - Non rechargeableNon rechargeable
Carbon Zinc Low power density & short shelf life D cell – 8Ah @ 1.5V Lowest cost
Alkaline Moderate power density & 5 year shelf life D cell – 18 Ah @ 1.5V Moderate cost
Lithium Thionyl Chloride High power density & 10 year shelf life D cell – 13 Ah @ 3.6V Highest cost Must use high rate versions for peak tx currents
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Secondary Batteries - Secondary Batteries - RechargeableRechargeable
Lithium-ion (Li-ion) Highest power density Highest cost Stringent charging requirements Good self-discharge rate Small form factor Limited peak current capability
Sealed Lead Acid (SLA) Most popular – well understood Good cost performance trade-
off Easier to recharge Lowest power density Lowest self-discharge rate Heavy
Nickel Metal Hydride (NiMH) Middle of the road Highest self-discharge rate
Nickel Cadmium (NiCd) High current applications High self-discharge rate Memory effects if not managed
correctly
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Solar CellsSolar Cells
Ensure adequate output to recharge batteries under all conditions. Cloudy days Short winter days Accumulation of dirt/snow/debris Orientation to the sun
Ensure battery capacity to cover long nights and cloudy days
Charge controller generally required Relatively expensive & fragile
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Things To WatchThings To Watch
Effects of temperature Many batteries lose capacity @ high or low
temperatures Minimum battery voltage at end of life
Ah ratings usually specify a minimum voltagePeak current
Many technologies typically cannot deliver the peak current required during transmit
Out gassing Batteries inside a sealed enclosure can explode
Accidental discharge A lot of energy in a very small package Product liability issues
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Specification Checklist - 1Specification Checklist - 1
Voltage It is important to know not only the nominal voltage, but also the
minimum and maximum for the application. As an example, a 7.2 volt nominal nickel metal hydride pack will vary from 6.0 volts in a fully discharged state to 9.6 volts at the end of charge.
Discharge Current Both the average and maximum discharge currents are needed to
specify the proper battery. Most often, the average current determines how large the battery must be to operate the device for a given amount of time. But in some cases there are intermittent high loads, and the maximum current requires a larger battery for the device to operate at all.
Cycle Life If the battery is rechargeable, the number of charges and
discharges required over the life of the battery will help determine the ideal chemistry and capacity.
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Specification Checklist - 2Specification Checklist - 2
Service Life For a non-rechargeable or a backup battery, the size and chemistry
will be determined by the required life, as well as the discharge and temperature profiles.
Cost A technically ideal battery could be cost prohibitive. Note, however,
that a more expensive battery can sometimes pay for itself several times over in the form of reduced replacement costs and/or better performance.
One-Time-Use or Rechargeable One-time-use or primary cells, once discarded must be replaced
with a fresh battery. Rechargeable or secondary cells can be used many times, but require a charger.
Charging Improper charging is the leading cause of early failure in
rechargeable batteries. A better charger will often pay for itself in increased performance and reduced replacement costs.
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Specification Checklist - 3Specification Checklist - 3
Weight & Dimension Cells of various chemistries are made in a wide variety of sizes,
and custom battery packs offer even more flexibility. Note that a smaller, lighter battery with the same energy usually costs more than a larger, heavier one, and even if money is no object, there is a limit to how small and light a battery can be.
Temperature If your product will be used or stored in hot or cold conditions,
battery performance and life could be affected. Low temperatures compromise performance, while high temperatures dramatically reduce the life of cells.
Storage Duration - Consider not only inventory turnover, but how long the
batteries will spend in the supply chain and in your customer's inventory before being used or recharged.
Conditions - What temperature and moisture conditions will your battery be stored under?
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Specification Checklist - 4Specification Checklist - 4
Self Discharge This is a measure of how quickly a cell will lose its energy
while sitting on the shelf. Note that higher temperatures will significantly reduce the shelf life of any battery.
Primary Batteries: Carbon 2.5 years Alkaline 5 years Lithium 10+ years
Rechargeable batteries: Lead acid 6 months between "top off charges“ NiCds 1 year between charges NiMH 1 year between charges Lithium 1 year between charges