Transcript Rechargeable Battery System (REBATEM)

Mid Semester Presentation
February 24, 2009
Team Members
Chapman, Jonathan
Dang, Quoc
Duties: Recharging
Duties: Cell Monitoring
Major: Electrical Engineering
Major: Computer Engineering
Grice, Quintin
Smith, David
Teeple, Richard
Duties: Power Circuit
Duties: Fault Protection
Duties: Communication
Major: Electrical Engineering
Major: Computer Engineering
Major: Computer Engineering
Project Origin
 This project stemmed from the curiosity
of Dr. Marshall Molen and the EcoCar
competition.
 Eight lithium ion cells
 CAN-bus (Control Area Network)
Overview:
 Problem
 Solution
 Constraints
 Technical
 Practical
 Approach
 Progress
Problem
 When dealing with lithium ion battery systems, the
following aspects must be taken into consideration:
 Safety

Fire and Explosion
 Communication

CAN-bus
 System Life

Weakest Link (individual cell)
Solution
 A rechargeable battery system that offers the
following:
 selective charging
 over-all current monitoring
 individual cell temperature and voltage monitoring
 CAN-bus communication
Technical Constraints:
Name
Description
Battery Technology
The technology used to output voltage from the REBATEM must be lithium ion
cells.
Accuracy
Voltage: 0 to 5 volts with a tolerance of ± 0.1 volts
Current: 0 to 80 amperes with a tolerance of ± 10 milliamps
Temperature: -30 to 200 degrees Fahrenheit with a tolerance of ± 2 degrees
Cycle Life /
Capacity
The REBATEM must maintain at least an 80% state of charge for the individual
cells and a minimum of a 400-cycle life.
Technical Constraints (cont.):
Name
Description
Fault Protection
Disconnect the cells from the system when temperature passes 175 degrees
Fahrenheit or when current passes 80 amperes. Charge cells up to 80% capacity.
Output
The output voltage must be within 14 to 16 volts. Current hour rating must be
between 3.4 and 3.8 amp hours.
Communication
The battery management system must communicate cell voltages, temperatures
and current to external devices.
Environmental
•Green energy
•Contains no toxic metals
• Cadmium
• Lead
•No toxic fumes released if improperly
disposed (incineration)
Safety
•Unstable - needs to be monitored
[1]
•Sony battery recalls
•UL 1642 states that users must be
protected from risk of explosion or fire due
to any instability of the Li-ion cells [2].
Cell Geometry
Prismatic
Cylindrical
[3]
VS
[4]
Cylindrical
Advantages
Disadvantages
 High energy density
 Poor heat dissipation
 Good mechanical
 Packaging must be
stability
 Can withstand high
internal pressure
designed around
available cell sizes
Prismatic
Advantages
 Can be shaped to fit
packaging restrictions
 Better heat dissipation
Disadvantages
 Lower energy density
 Higher manufacturing
costs
 No venting system to
release internal
pressure
Types of Lithium ion Cells
 Cobalt  Manganese  Polymer  Phosphate
Chemistry
Nominal
Voltage
Maximum
Voltage
Energy density
Wh/kg
Life Cycle
Cobalt
3.6V
4.20V
110-190
300-500
Manganese
3.7-3.8V
4.20V
110-120
> 500
Polymer
3.7V
4.20V
120 - 160
> 1000
Phosphate
3.2-3.3V
3.6V
95-140
>800
[5]
Cell Configuration
 Series of eight
 Eight in parallel
 Two series of four in
parallel
 Four series of two
in parallel
Evaluation:
Output
Voltage
Output
Current
Amp Hours
Series of eight
28 - 32 V
10 - 20 A
1.9 - 2.1 Ah
Eight in parallel
3.6 - 4 V
80 - 160 A
15.2 - 16.8 Ah
Series of four in parallel
14 - 16 V
20 – 40 A
3.8 – 4.2 Ah
Series of two in parallel
7-8V
40 – 80 A
7.6 – 8.4 Ah
Temperature Sensing
 Thermocouples
 Resistance Temperature Detector (RTD)
 Thermistors
 Integrated Circuit (IC)
Temperature Range
Cost (each)
0° to 1250° C
>$2
RTD
-196° to 788° C
> $2
Thermistors
-45° to 260° C
<$2
IC
-45° to 150° C
<$2
Thermocouples
Voltage Sensing - BMS Chip
 Pros
 Less control lines
 Measures temperature
and current
 Cons
 Extra communication
 Single cell monitoring
[6]
DS2762 High-Precision Li+ Battery Monitor
Charging
 Discrete Components
 Complex
 Potentially unsafe
 Already been done in a simpler format
 Integrated Circuit
 Independent voltage and current loops
 Stand alone or uses microcontroller
 Built-in linear regulator power microcontroller
 Monitors charge current
Summary
[6]
 BMS: DS2762
 Charging Sensor: Max8677c
[7]
 Cells: PL603495K
[8]
Timeline
January
Research
Ordering
Parts
Hardware
Design
Constructing
and test
Prototype
Working
Prototype
February
March
April
References:
[1] [Online] Available: http://www.gadgetreview.com/wp-content/uploads/2006/08/explosion_dcrop1.jpg.
[2] “Lithium Batteries.” [Online]. Available: http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=1642.html.
[3] "Li - ion Battery." [Online] Available: http://www.global-b2bnetwork.com/b2b/88/89/445/page6/48031/li_ion_battery.html.
[4] "INOVA T4 Tactical Flashlight." [Online] Available: http://flashlightsunlimited.com/inovat4.htm.
[5] “The high-power lithium-ion.” [Online] Available: http://www.batteryuniversity.com/partone-5A.htm.
[6] “Hi-Power Polymer Li-Ion Cell.” [Online] Available:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4391.
[7] [Online] Available: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3950.
[8] http://www.maxim-ic.com/quick_view2.cfm/qv_pk/3950/t/al
Any Questions?