State of the Art Battery Charger

1
State of the Art Battery Charger
2/6/2003
TeamMay 03-05

• Team
• Richard Musumhi
• Bo Bo Oo
• Pascal Openshaw
• Chris Privitere

Advisors Dr. John Lamont Dr. Richard Patterson
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Presentation Outline

• Overview
• Assumptions, limitations
• Activities
• Research, design
• Time and money
• Budget, personnel
• Conclusion
• Additional work, summary

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Definitions

• PIC
• Peripheral Interface Controller
• Smart device
• Able to make decisions based on inputs
• NiCad, NiMH
• Most common rechargeable batteries on the market,
  Nickel Cadmium and Nickel Metal Hydride

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Project Overview

• What is a battery charger?
• Takes discharged batteries and restores their
  chemical properties using an alternate source of
  power, such as the sun or a wall outlet.
• The need for a new charger
• None of the chargers on the market have as full a
  feature set as the one that our group has
  designed.

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Problem Statement - Needs

• Need a battery charger that is
• Small
• Portable
• American, European, or car powered
• Charge 1-4 AA/AAA NiCad or NiMH batteries in 1-2
  hours

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Problem Statement - Tasks

• We need to
• Convert the power
• Charge the battery
• Sense when to stop charging the batteries
• Control the system

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Problem 1 Power Transform

• External power
• 12V
• Commercial 120V and 220V wall adapter
• Commercial 12V car adapter
• Internal power
• DC to DC converter to 6V and 3V
• User does not notice

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Problem 2 Charging control

• Layout

Peripheral Interface Controller
Digital-to-Analog Converter
Current controllers
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Problem 3 Stop charging?

• NiCad A voltage drop
• NiMH A temperature rise
• Safeguards
• Combine both
• Max timer
• Code checks

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Problem 4 Control the System

• Choices
• Pre-built microchip
• Microprocessor
• State machine
• The group decided to use a PIC microcontroller
  with appropriate code and control.

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The Charger

• Working final product ugly, based on breadboard
  with plenty of wires
• Commercial final product attractive, cool
  design, portable.

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Operating Environment

• Used indoors or in a vehicle
• Can not be used in extreme heat, cold, or wet
  conditions

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Intended Users and Uses

• Designed for the frequent picture taker or other
  user of electronic equipment
• Batteries run out frequently
• Charger will charge the batteries quickly without
  damaging them

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Assumptions

• Power sources are 120V/220V AC or 12V DC
• Charger will charge 1-4 batteries
• Charger is only needed indoors or in a vehicle

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Limitations

• 100 budget
• The batteries used do not have smart
  capabilities.
• The charger cannot draw so much current that it
  would kill a car battery.

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End-Product Description

• Battery charger that can be used on 120V or 220V
  AC and 12V DC
• Can charge 1-4 batteries in 1-2 hours
• Portable and easy to use

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Project Activities

• Definition
• Research
• Design
• Implementation
• Testing
• Final Product, yay!

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Presentation Accomplishments

• Design Spec 80
• Components bought 70
• Software programming 0
• Implementation 0
• Testing 0

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Approach considered and used

• PLAN A
• Use a microchip MAX 713
• Requires no programming
• Batteries can only be charged in series
• Minimum of two batteries
• Fewer options

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PLAN B

• Use microchip DS 2770
• Charges exactly 3 NIMH cells at a time
• Capable of charging Lith-Ion battery
• Temperature terminated
• Expensive

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PLAN C

• PIC microcontroller
• Voltage and temperature sensors
• Software programming for greater flexibility
• One battery at a time
• More expensive

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Decisions, decisions

• Plan C wins
• The PIC microcontroller provided the most
  flexibility and options to the team.

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Definition Activities

• Most important requirement
• Should be able to operate on 120v ac/60Hz, 12v
  DC, 220v ac/50Hz.
• Charge AA/AAA.
• Discharge/conditioning
• Trickle charge
• Portable

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Design Activities

• External transformer
• Convert 120/220V to the 12V
• Internal transformer
• Change 12V to internal levels needed
• Circuit
• Various digital to analog converters, current
  controllers, and sensors
• Software
• State machine to start and terminate fast battery
  charging

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Research Activities

• Handbook of Batteries,third edition.David Linden
  and Thomas B.
• Reddy,McGraw-Hill,New York 2002
• John Oeler,john.oeler_at_dalsemi.com
• For Dallas technical support

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Implementation Activities

• Purchasing
• Most components purchased
• Circuit board setup
• Software testing
• Software upload
• Final product should function on its own without
  any glitches

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Testing Activities

• Digital to Analog accuracy
• Current control accuracy
• Detecting voltage and temperature changes
  properly
• Properly charge 10 batteries
• No overheating

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Testing Activities continued

• Detect insertion/removal of a battery causing
  circuit to be reset.
• Final product functionality

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Resources - Personnel
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Resources - Financial
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Risks Risk Managements

• The loss of team member
• Document work
• Microprocessor might not be useful
• Alternatives
• Delays in product shipments, damage of parts
• Purchase extras and in advance

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Lessons learned

• Start early
• Communication is important
• Manage time efficiently
• Good documentation
• Get help from faculty advisors

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Additional work

• Create a generic design that can be
  commercialized
• Optimize the cost for mass production
• Increase capabilities

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Commercialization

• - 12 V wall adapter 10.00
• - 12 V car adapter 7.00
• - plug receivers 1.00
• - DC to DC converter 6.00
• - DAC 7.50
• TOTAL 49.00

• Device cost
• - PIC 4.50
• - LEDs 1.00
• - battery monitors 7.00
• - LED driver 4.00
• - transc amps 1.00

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Commercialization cont.

• Estimated total cost, no bulk
• 49
• Distributor price
• 70
• Retail Price
• 90

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Project Summary

• State-of-the-art battery charger
• Can be used worldwide
• Easy to use
• Portable
• 1 year of development

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State of the Art Battery Charger
2/6/2003
TeamMay 03-05
Questions?

• Team
• Richard Musumhi
• Bo Bo Oo
• Pascal Openshaw
• Chris Privitere

Advisors Dr. John Lamont Dr. Richard Patterson