Challenge X Selective Battery Charger

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Challenge X Selective Battery Charger
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Team
Dr. Marshall Molen - Advisor
Brandon Holbrook
Daniel May
Charging Circuit Software Web Site Microcontroller
Graphics Algorithms Software Web Site
Brandon Gore
Heath Massey
Interfacing Power Supply Charging Circuit PLDs
Software PLDs Microcontroller Interfacing
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Introduction

• Simple Concept
• Hybrid Electric Vehicles (HEVs) use batteries as
  a source of power for the electric motor.
• The electric motor acts as a generator to
  recharge the batteries.

• General Information
• Batteries are charged by applying reversed
  current.
• While the battery is being charged, the voltage
  across the battery terminals increases.
• While the battery is being discharged, the
  voltage across the battery terminals decreases.

-
Discharge
Charge
-

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Problem

• If a battery is over-charged, the internal
  chemistry of the battery is compromised. How can
  over-charging be prevented?
• use two stages of charging fast-charge and
  trickle-charge
• monitor battery characteristics such as voltage,
  temperature, and time, and estimate
  state-of-charge
• make charging decisions based on the estimated
  state-of-charge

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Existing Technology

• Cobasys
• Develops battery-charging systems for specific
  types of vehicles.
• Each application requires a separate
  battery-charging system

• How is our system better?
• One battery-charging system can be used for any
  vehicle.
• Our system will work with different types of
  batteries.
• Batteries can be added or removed based on the
  power needs of the application. Our system will
  dynamically adapt to the changes.

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Approach
Microcontroller
Programmable Logic Devices
Monitors
Battery Packs and Power Supply
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Battery Packs

• Purpose of the Batteries
• provide power for the HEVs electric motor

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Battery Packs

• 12-volt packs
• 8.5 Ah charge capacity
• 23 total packs (276 volts)
• 80 kW maximum output
• SOC will be kept between 20 and 80

Items in blue indicate a design constraint
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Power Supply

• Purpose of the Power Supply
• supply electronic devices (microcontroller,
  PLDs, monitor circuit) with 5W.
• control incoming generated current (from braking
  or engine) for charging
• provide two charging currents to batteries
  (fast-charge, trickle-charge)

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Monitors

• Purpose of Monitors
• monitor characteristics of each battery pack 10
  times a second
• monitor temperature which will not exceed 50º C
  (using thermistors)
• monitor voltage across battery terminals
• direct appropriate current to battery pack while
  charging (fast-charge, trickle-charge)

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Programmable Logic Devices

• Purpose of the PLDs
• collect data from the monitor circuit
• make data available to microprocessor
• interpret commands from microprocessor to
  monitor circuit

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Programmable Logic Devices Software
Yes
No
No
Collect Input Data
Put Data on Output Bus
Ver?
Mode?
Yes
No
Set Charge Mode Off
Chrg?
Yes
Wait for Address
Send Ack
Mine?
Start
Yes
No
Set Charge Mode On
Wait for Ready
Wait for Ready
Send Ack
Ack Acknowledgment Ver Communication
Verification Chrg Charge Mode Mode Mode Change
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Microprocessor

• Purpose of the Microprocessor
• process data provided by the PLDs
• estimate state-of-charge
• decide when to charge based on estimated
  state-of-charge
• send warnings/errors to CAN interface

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Microprocessor - Software
Battery State Voltage (Samples for 10
Seconds) Temp. (Samples for 10 Seconds) Voltage
Average Temp. Average Voltage Average of all
Batteries Temp. Average of all Batteries State-of-
Charge Before Last Charge Time Since Last
Charge Estimated State-of-Charge
Start
End
Check Monitor Comm.
Send Error to CAN
No
Ok?
Yes
Next Address
No
Resp?
Yes
Collect Data From PLDs
Add Data to Battery State
Switch Charge Mode
Resp Response Chg Toggle Charge Mode
Yes
No
Determine State-of-Charge
Update Battery State
Chg?
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Cost
Cost of System
Cost of Batteries The cost of the batteries will
range from 8000-10000.
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Goals for the End of the Semester

• complete a small-scale (low-voltage) battery
  system
• apply the battery system to low-power device to
  show that the system can be used for a wide
  variety of applications
• demonstrate the charging algorithm visually on a
  laptop
• demonstrate the dynamic adaptation to different
  number of battery packs

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Summary

• Most of todays HEV battery-charging systems are
  specific to a certain type of vehicle.
• Our system can be used in any vehicle. The power
  output can be changed by adding or removing
  battery packs.
• The overcharging of batteries will be prevented
  by monitoring temperature and battery pack
  voltage.
• Each battery pack will be monitored individually
  to ensure optimized efficiency. Hence the term
  selective.

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Acknowledgments

• Dr. Marshall Molen
• Philip Conley
• Dr. Joe Picone
• Tom Vaught (DRS Technology)

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Questions