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Mid Semester Presentation
Team Members
Chapman, Jonathan
Dang, Quoc
Duties: Recharging Circuit
Duties: Power Circuit, Website
Major: Electrical Engineering
Major: Computer Engineering
Grice, Quintin
Smith, David
Teeple, Richard
Duties: Power Circuit
Duties: Fault Protection,
Documentation
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.
 8 Lithium ion cells
 CAN-bus
Overview:
 Problem
 Solution
 Constraints
 Technical
 Practical
 Approach
 Progress
 References
 Questions
Problem
 When dealing with Lithium ion technology, the
following aspects must be taken into consideration:
 Safety
 Communication
 System Life
Solution
 A cost efficient 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 must be measurable between 0 and 5 volts with a tolerance of ± 0.1 volts.
Current must be measurable between 0 and 80 amperes with a tolerance of ± 10
milliamps. Temperature must be measurable between -30 and 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.
Fault Protection
The control mechanism must disconnect the cells from the system when the
temperature rises above 175 degrees Fahrenheit or when the current through the
cells passes 80 amperes. It must also prevent overcharging a cell by slowing the
charge rate when the cell’s state of charge reaches 80%.
Output
The REBATEM’s output voltage must be within the range of 14 to 16 volts. Its
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.
Economic
If mass produced on its current scale, the
REBATEM must be affordable to the general
public. A target cost of $250 provides a small
profit of approximately $100. Parts alone
must cost no more than $150.
Safety
The device must meet the standards of UL
1642, which states that users must be
protected from risk of explosion or fire due to
any instability of the Li-ion cells [1]. Cell
monitoring must ensure that the temperature
remains within a safe operating range to
uphold this UL specification.
Cell Geometry
Cylindrical
Prismatic
[1]
VS
[2]
Prismatic
Advantages
Disadvantages
 Can be shaped to fit
 lower energy densities
packaging restrictions
 Better dissipater heat
 Higher manufacturing costs
 No venting system to release
internal pressure build-up
 Must use heavier metal to
prevent bulging from
pressure build-up
Cylindrical
Advantages
Disadvantages
 High energy density
 Poor dissipater of heat
 Good mechanical stability
 Packaging must be designed
 Can withstand high internal
pressure build-up
 Resealable venting system
around available cell sizes
Types of Lithium ion Cells
 Cobalt  Manganese  Polymer  Phosphate
Pros and Cons:
Chemistry
Nominal
Voltage
Charge
Voltage
Limit
Energy
density
Wh/kg
Cobalt
3.6V
4.20V
110-190
Manganese
3.7-3.8V
4.20V
110-120
Polymer
3.7V
4.20V
120 - 160
Phosphate
3.2-3.3V
3.6V
95-140
[5]
Cell Configuration
 Series of eight
 Eight in parallel
 Series of four in
parallel
 Series of two in
parallel
Evaluation:
Output
Voltage
Continuous
Current
Peak
Current
Amp Hours
Series of eight
28 - 32 V
10 - 20 A
38 - 40 A
1.9 - 2.1 Ah
Eight in parallel
3.6 - 4 V
80 - 160 A
304 - 320 A
15.2 - 16.8 Ah
Series of four in
parallel
14 - 16 V
20 – 40 A
76 – 80 A
3.8 – 4.2 Ah
Series of two in
parallel
7-8V
40 – 80 A
152 – 160 A
7.6 – 8.4 Ah
Temperature Sensing
 Resistance Temperature Detector (RTD)
 Integrated Circuit (IC)
Pros and Cons:
RTD
IC
Supply
Voltage
Supply
Current
Temperature
Range
Cost
(each)
< 10V
< 1mA
-200 - 1475 ˚F
> $2
5.5- 28 V
0.28 - 8 A
-50 – 300 ˚F
<$2
Charging
 Integrated Circuit (IC)
 Independent Voltage and Current Loops
 Stand Alone or Uses Low-Cost μC
 Built-In Linear Regulator Power μC
 Charging-Current-Monitoring Output
Cell Geometry
Prismatic
[1]
Cylindrical
[2]
Type of Cell
Hi-Polymer Li-ion cells
Specifications
Specifications
[3]
Capacity
1.9-2.1 mAh
Cycle life
> 500
Charge rate
1.9 A Max.
Discharge
Rate
38 A Max.
Size
6.0X35X96
mm
Weight
1.4 oz (40 g)
[3]
Temperature Sensor
RTD
Integrated Circuit
[7]
[6]
Timeline
January
Research
Ordering
Parts
Hardware
Design
Constructing
and test
Prototype
Working
Prototype
February
March
April
May
References:
[1] "Li - ion Battery." [Online] Available: http://www.global-b2bnetwork.com/b2b/88/89/445/page6/48031/li_ion_battery.html.
[2] "INOVA T4 Tactical Flashlight." [Online] Available: http://flashlightsunlimited.com/inovat4.htm.
[3] [Online] Available: http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4391
[4] “Battery packaging - a look at old and new systems ”[Online] Available:
http://www.batteryuniversity.com/partone-9.htm
[5] “The high-power lithium-ion” [Online] Available: http://www.batteryuniversity.com/partone-5A.htm.
[6] [Online] Available:
http://upload.wikimedia.org/wikipedia/commons/8/80/Three_IC_circuit_chips.JPG.
[7] [Online] Available:
http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMvhQj7WZhFIAOPwZSj%2fjTA
nXLEDpLtU15A%3d
Any Questions?