Daniel Miersma's Senior Project Final Report

S E N I O R P R O J E C T F O R M E C H A N I C A L E N G I N E E R I N G
E G R 4 8 1 / 4 8 2
F R I D A Y , M A R C H 1 6 , 2 0 1 2
ME 427 PROJECT
COORDINATOR
FHSAE ELECTRONIC COOLING SYSTEM
(FINAL REPORT)
P R E P A R E R :
Daniel Miersma
Bronco ID: 004186455
Address: 926 Frontier Ave.
Redlands, CA 92374
Phone: 909-801-9248
E-mail: dhmiersma@csupomona.edu
P R O J E C T A D V I S O R :
Dr. Angela C. Shih
Office: 17-2344
Phone: ###-###-####
E-mail: acshih1@csupomona.edu
P R O J E C T P A R T N E R S :
Grant Feenstra (Unofficial)
Patrick Donovan (Unofficial)
FHSAE team
ME 427 Thermal Design class
L O C A T I O N :
California State Polytechnic University, Pomona
Address: 3801 West Temple Avenue
Pomona, CA 91768

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E X E C U T I V E S U M M A R Y
The purpose of this project is to design and fabricate the cooling system for the 2011-2012 Cal
Poly Pomona Formula Hybrid SAE team’s car; more specifically, the cooling system for the electronics
being used. Main electrical components of concern are:
7.2 Volt Lithium Ion Battery Packs (x4)
3000 Farad/2.7VDC Boost Capacitors (x14)
150 Watt DC-DC 10-32v to 12-35v Converter Boost Chargers (x20)
There is very limited space available within the car frame to locate these components. The team
has requested that the batteries and boost capacitors not be placed along the side of the vehicle. As a
result, and due to space constraints, the batteries will be placed on the floor between the driver’s seat and
the 250cc Ninja 250R internal combustion engine. The boost capacitors will be placed above the Ninja
250cc engine, behind the head of the driver. The DC-DC converters will be placed along the right hand
side of the vehicle above the battery duct.
The battery packs will be air cooled by flowing air directly through the pack, allowing moving air
to come into direct contact with the 18650 lithium-ion cells. Air flow will be channeled through the
batteries through the use of air ducts placed on either side of the vehicle. Each duct will direct air through
two battery packs lying horizontally on top of each other. Air flow will be initiated through the use of
one fan in each duct. This fan is a Sanyo Denki San Ace 60 12volt DC PWM controlled fan (Model
#9GV0612P1G03). It provides the flow rate and pressure necessary to cool and push the air through the
battery packs, even under peak loads. Fan speed will automatically adjust based on the temperature
within the battery packs. This will be done via temperature sensors within the battery packs and a PWM
controller. An aluminum mesh filter will be placed within each duct to prevent water and debris from
entering the battery packs and housing area. All four battery packs will be placed within a polycarbonate
battery box. Battery connections, wires, and contactors will be placed within the battery box in the area
between the two sets of battery packs. Air entering the battery packs from both sides of the vehicle will
exit the battery packs into the center area of the battery box. It will then exhaust through a slot in the
bottom of the battery box in the very rear. Fast moving air beneath the vehicle will create a low pressure
point and act as a vacuum, sucking the air out of the battery box.
The boost capacitors will not generate enough heat to necessitate the need for forced convection
cooling. Thus, they will be housed within a polycarbonate housing without any fans or air ducts to
channel air flow over them. Holes will be drilled into the bottom of the capacitor housing and slots cut
into the top of the housing below the cover to allow for free convection cooling.
The DC-DC converters will be configured into two stacks of 10. The housing will allow for an
area between the two stacks of DC-DC’s for wires to travel. Each row of DC-DC’s will also be housed
within its own air channel. This air channel will be walled off from the wires going through the center of
the housing assembly and have its own fan to create air flow over them. Thus, the whole DC-DC housing
assembly will consist of two fans, one for each stack. These fans are Sanyo Denki San Ace 60 12volt DC
PWM controlled fans (Model #9GV0612P1H03). They provide the flow rate and pressure necessary to

iii
cool and push the air through the DC-DC channels. Fan speed will automatically adjust based on the
temperature of the DC-DC’s. This will be done via temperature sensors placed on the DC-DC’s and a
PWM controller. An aluminum mesh filter will be placed at the entrance and exit of each duct to prevent
water and debris from entering the DC-DC housing area.
Dr. Angela Shih’s two 2012 Winter quarter ME 427 Thermal Design classes were also involved
in this cooling design project. Each class was split into two major groups; each major group was split
into four minor groups. Each major group represented a different company working on a total cooling
design for the Cal Poly Pomona Formula Hybrid SAE team. Each minor group represented the four sub-
system teams: battery pack cooling, capacitor cooling, DC-DC converter cooling, and heat
shielding/firewall design to protect the driver and electronic components from the heat of the Ninja IC
engine. Thus, there were a total of four “companies” working on a total cooling system design for our
team.
My job was to act as an engineering representative from the Formula Hybrid team. I provided the
basic information necessary for them to start on their design. I also was available to answer any questions
they may have had about how things worked, what was needed, testing data results, etc. I also sat in on
design reviews and critiqued their designs.
Although I was working on my own cooling system design parallel to the Dr. Shih’s thermal
design classes, I was able to borrow some data and design ideas from them and incorporate them into my
own design to use on the actual car.

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L I S T O F C O N T E N T S
TITLE PAGE .........................................................................................................................................i
PREPARER............................................................................................................................................... i
PROJECT ADVISOR.................................................................................................................................. i
PROJECT PARTNERS ............................................................................................................................... i
LOCATION .............................................................................................................................................. i
EXECUTIVE SUMMARY .......................................................................................................................ii
LIST OF CONTENTS ............................................................................................................................iv
FHSAE ELECTRONIC COOLING SYSTEM ...............................................................................................1
INTRODUCTION..................................................................................................................................... 1
LITHIUM-ION BATTERY PACKS .............................................................................................................. 2
BOOST CAPACITORS.............................................................................................................................. 9
DC-DC CONVERTERS ........................................................................................................................... 11
ME 427 THERMAL DESIGN CLASS INVOLVEMENT .............................................................................. 15
CONCLUSION....................................................................................................................................... 17
REFERENCES ....................................................................................................................................19
APPENDIX .......................................................................................................................................21
APPENDIX 1 – BATTERY DESIGN DEPICTIONS..................................................................................... 21
APPENDIX 2 – BOOST CAPACITOR DESIGN DEPICTIONS .................................................................... 23
APPENDIX 3 – DC-DC CONVERTER DESIGN DEPICTIONS .................................................................... 25
APPENDIX 4 – FULL VEHICLE DESIGN DEPICTIONS ............................................................................ 28
APPENDIX 5 – BILL OF MATERIALS...................................................................................................... 31
APPENDIX 6 – SAMPLE CALCULATIONS .............................................................................................. 32

1
F H S A E E L E C T R O N I C C O O L I N G S Y S T E M
I N T R O D U C T I O N
In designing the electronics cooling system, certain steps need to be taken. The first thing that
needs to be done is determine the amount of load each component will be under while in operation. This
includes everything from the load experienced during our sprint event where all power is maxed, to
driving the car during the endurance event, to charging the car while it sits still.
The second step, before actual testing should be performed, is to find out the maximum loads and
temperatures the individual components may experience before they begin to fail and/or cause damage.
The third step is to determine the efficiency and heat generation of each electrical component.
This allows us to determine how much of the energy is being lost to heat and needs to be dissipated.
Fourth, the surface temperatures of critical components should be measured while under load to
aid in heat transfer calculations. If load simulation is not possible, then research and data from third
parties must be used to estimate temperatures during different loads.
Fifth, a maximum ambient outdoor temperature should be established to design around. For this
project, 40° C (104° F) was the goal to design around. The temperature was eventually lowered to 35°C
(95° F) to aid in component cooling.
Sixth, calculations and/or CFD analysis must be performed to determine the velocity and volume
of airflow necessary to keep the electrical components below their peak allowable temperatures even
while under maximum loads. The pressure drop of the fluid through the system must also be determined
so that proper fans or pumps may be selected. These calculations and analyses will ultimately lead to the
physical parameters of the air ducts, component housing geometry, and fans necessary for the cooling
system. It may also lead to the determination that another means of cooling, other than just air, may be
necessary (i.e. a liquid or even refrigerated system).
One more article that must be taken under consideration is protection from the elements, namely
rain. Thus, the entire system must be designed so that no water, either from rain above or the road
beneath the car, may come into contact with the electronic components.
All designs must be manufacturable, affordable, as light weight as possible, not conflict with any
of the official Formula Hybrid SAE event rules, be as compact as possible, and cooperate with all the
other components on the vehicle.
The cooling system must be designed in cooperation with the FHSAE team, including the control
system engineer Patrick Donovan, the design captain Grant Feenstra, the club president John Tran, the
aerodynamic and aesthetic team Charlie Welch and Akash Chudasama, and every other team member
designing and working on the car. Dr. Angela Shih should be approached for any necessary advising and
final design critiquing as she is the advisor for this project.

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L I T H I U M - I O N B A T T E R Y P A C K S
The batteries used to power our electric motor are four AC Propulsion 53P-2S lithium-ion battery
packs. Each pack has a nominal voltage of 7.2 volts and a capacity of 100 amp-hours [4], [16]. Each
pack consists of two blocks of 53 18650-type li-ion cells. The 53 cells in each block are connected in
parallel with each other and each block of 53 cells is connected in series. Thus, each battery pack consists
of a total of 106 18650 cells.
To clarify what an 18650-type cell is: it is a specific size and shape designation for a battery.
Namely, it is a cylindrical battery that is 18mm in diameter and 65mm in length; a little bit bigger than a
AA battery [4].
The first step was to determine the load that would be placed on the batteries during different
events. The three different loads our batteries would experience would take place during charging, the
sprint event, as well as the autocross and endurance events. The battery packs would be charged at 50-
60amps over a period of about 2 hours. The sprint event would ideally require the maximum output the
batteries are capable of safely producing, 200amps, for a period of 10 seconds. The autocross and
endurance events require a wide range of loads as the vehicle slows down into corners and speeds up out
of them. The average load desired for these events was estimated to be around 100amps for 30 minutes.
Originally, a goal of a 200amp average discharge rate was given for the autocross and endurance
events and a 400amp discharge for the sprint event. This, however, proved to create a massive amount of
heat generation, which would have necessitated the use of extreme measures for cooling. Such options
included liquid cooling, a refrigerated air conditioning system, or very powerful fans. Neither of these
options were viable solutions as they would induce a lot more weight, take up valuable space, require a lot
of power to run (thus only increasing the problem), or require liquid coolants that were not allowed in the
FHSAE rules [3].
The average desired load on the battery packs for the autocross/endurance and sprint events were
lowered to 100amps and 200amps respectively for a few reasons. First and foremost, the heat generation
of the battery packs had to be lowered dramatically. Secondly, the electric motor was only rated to run
continuously up to 150amps. Thirdly, the maximum rated discharge for the battery packs is 2C [4], [16],
or 200amps. Thus, the batteries would have to be discharging above their maximum rating regularly if
they were to discharge at an average of 200amps.
The load which would generate the most heat was during the autocross/endurance events. Thus,
most analysis was done assuming loads during these events.
The second step of thermal analysis, which involves the finding out of the maximum load and
temperatures allowed by the component, was visited already in the first step as our desired loads exceeded
the allowable loads of the battery packs themselves. Thus, the first step of determining the usage loads
was determined by the second step. Maximum allowable discharge for each battery pack was 200amps
[4], [16] and the maximum temperature for the battery packs, as recommended by AC Propulsion, was
50° C [16]. The specification chart for the individual 18650 cells within the battery pack specify a
maximum discharge temperature of 65° C [4]. The design goal was to have the battery packs reach a
temperature of no more than 50° C under any circumstances.

3
The third and fourth steps involve finding the heat generation and resulting battery temperatures
during desired loads. Heat generation for electronic components is often referred to as I2
R losses [19].
This is because I2
R is the equation for heat generation, where “I” is the current passing through the
component and “R” is the internal resistance or impedance of the component.
EQUATION 1 [19]: 𝑃𝑜𝑤𝑒𝑟 𝐿𝑜𝑠𝑠 (𝐻𝑒𝑎𝑡 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛) = 𝐼2
𝑅 [𝑊𝑎𝑡𝑡𝑠]
The desired current running through the batteries was known, but the impedance of the cells was not.
Research revealed a range of typical impedances for new 18650 li-ion cells. Values ranged from 120mΩ
[11] to 180mΩ [2]. AC Propulsion claimed their cells had an impedance of around 106mΩ [6].
However, we had a suspicion that the battery packs we had been given by AC Propulsion were old and/or
used. Since the impedance of lithium-ion cells tends to increase with age and number of charge cycles,
we decided to perform some heat tests on them.
The equation used to analyze the results of the heat tests was:
EQUATION 2 [19], [12]: 𝐼2
𝑅 [𝑤𝑎𝑡𝑡𝑠] =
𝑚𝐶 𝑝∆𝑇
𝑡
[𝑤𝑎𝑡𝑡𝑠]
Where, ”I” is the current through an individual cell, “R” is the cell’s internal impedance, “m” is the cell’s
mass, “Cp” is the cell’s specific heat, “ΔT” is the resultant change in temperature in °C, and “t” is the
length of the test in seconds. Thus, for a given test, if I, m, Cp, ΔT, and t are known, then theoretically,
the value of R can be found. This equation assumes that there are no heat losses: a completely insulated
and adiabatic process. Thus, for our test to work, we would have to completely insulate our batteries.
The 18650 cell data sheets provided to us listed a mass per cell of 45 grams [4]. This left for one
more unknown remaining to be found: Cp. Research revealed specific heat values for lithium-ion 18650
cells to be between 0.73 J/g·K [14] – 0.925 J/g·K [11]. Using the higher end value would be the most
conservative approach as it would result in the highest R-value. Thus, Cp=0.925 J/g·K was used.
For the test, two battery packs were wrapped in aluminum foil, then wrapped in blankets, and
finally placed into an ice chest. This would insulate the batteries and try to keep any heat from escaping
during the test. A temperature sensor inside each battery was used to monitor the internal temperature of
each of the batteries during the test. A load was placed on the batteries and a shunt used to ensure that the
battery packs discharged at exactly 40amps. After a period of 75 minutes, one battery pack had risen
12°C, while the other pack rose 11.5°C. The higher of these two values was used. Using Equation 2 and
inputting the values gained from our test and research, a resultant R-value of 195mΩ was calculated. This
was quite a bit higher than the value of 106mΩ [6] that AC Propulsion has claimed, thus supporting our
suspicion that the battery packs were old and/or used.
Joshua Allen from AC Propulsion, when presented with our test and resultant data, wrote:
“These are modules that were part of a batch that were built for a
customer but they were outside the customer's impedance tolerance so
it's not surprising that the impedance is a bit higher than normal.
Also, they've been sitting on a shelf for at least 12 months. If you can
tell me the serial number, I can confirm their age.
One other thing to consider is that our impedance test is done at 3.65V

4
and the duration is relatively brief. The values that you saw were an
average over the duration of the test and the impedance increases as the
voltage drops.” [5]
This confirmed our suspicion. Using an impedance of 195mΩ per cell, heat generation values could
finally be calculated.
A second, free convection test was performed to determine how much heat was escaping through
free convection. Two battery packs were used standing vertically so that the open ends of the batteries
were facing up and down. This configuration was the most efficient for free convection cooling because
heat was allowed to escape through the top as the heated air rose, while cool air was allowed to enter
through the bottom. The battery packs were again given a 40amp load. Ambient temperature during the
test was 72°F (22.22°C). At the start of the test, the cells were cooler than ambient temperature, thus
results were taken from the moment the cells reached ambient temp to the end of the test. The cells
reached ambient temperature 38 minutes into the test. The test ran for another 62 minutes from which
point they saw a temperature rise of 7.27°C. The temperature rise plot was not linear as it was for the
insulated battery test, but rather it was polynomial and very gradually seemed to approach some steady
state temperature. An equation for the curve of the temperature rise was generated using Excel:
EQUATION 3: 𝑦 = −0.0004𝑥2
+ 0.262𝑥
This equation could be graphed along with the equation generated from the insulated test:
EQUATION 4: 𝑦 = 0.2795𝑥
Figure 1 depicts these two curves.
FIGURE 1: INSULATED VS. FREE CONVECTION TEMPERATURE
RISE OF LI-ION BATTERY PACKS
S O U R C E : AC P R O P U LS I O N 5 3 P - 2 S C FD A N A L Y S I S # 4
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
0 20 40 60 80 100 120 140
ΔT(°C)
Minutes
Temperature Rise vs. TIme (40amp Load)
Free Convection
Insulated

5
Even with the small load, free convection was not enough to keep the batteries from a significant
temperature rise. In fact, even after 120 minutes, the batteries would not have reached steady state. The
plastic housing that the cells were housed in appeared to insulate them well. In reality, the batteries
would be lying down horizontally and all four battery packs would be housed within a small plastic
container on the car. This would significantly decrease the amount of free convection that could occur
within the battery packs. It was decided to assume the batteries would be nearly completely insulated
when on the vehicle.
Assuming the batteries were insulated, temperature rises for each of the three load scenarios were
calculated to determine what would affect the temperature of the batteries the most. Ideally, the battery
packs were to be charged at a rate of 50-60amps for a period of 2 hours when completely dead. They
would be discharged at a rate of 200amps for 10 seconds during the sprint events. The endurance and
autocross events take place around a curvy track where the driving style was estimated to be a constant
alternation between full throttle and braking. A full throttle currant draw of 150amps was assumed
because 150amps was the maximum that the motor was rated to run at continuously. A duty cycle of 65%
was assumed along with a driving time of 30 minutes.
During charging at 60amps, the battery packs were estimated to each generate 26.5 Watts of heat
and rise in temperature by 43.2°C after 2 hours.
During the sprint event, discharging at 200amps, the battery packs were estimated to each
generate 294.3 Watts of heat and rise in temperature by 0.68°C after 10 seconds. This rise was very
minimal, and thus the sprint event was not of much concern in the cooling design.
For the autocross and endurance events, a 65% duty cycle was assumed at a load of 150amps. At
150amps, the battery packs were estimated to each generate 165.6 Watts of heat. 65% of this heat would
be around 106 Watts of heat generation. This happens to be similar to the amount of heat generation that
would occur if the batteries were under a constant 120amp load. Thus, calculations were done assuming a
constant 120amp load for these events. (Note that the 65% duty cycle was applied to the heat generation
and not to the amperage draw. A 65% duty cycle applied to the amperage draw would suggest an average
draw of 97.5amps. At a constant 97.5amps, the batteries would only be producing around 70 watts in
heat. This would be an incorrect estimation of the actual heat generation given how the vehicle would be
driven.) Using these assumptions, the temperature rise of the battery packs after 30 minutes of run time
was estimated to be 43.2°C. This was the same temperature rise as was estimated in charging the
batteries. Thus, charging and the running of the autocross and endurance events seemed to each pose a
similar threat to the temperature rise of the batteries.
It was concluded to design the cooling system of the batteries around the autocross and endurance
events because the temperature rise was much more dramatic than that during charging. One thing was
certain: cooling was needed, especially if the car was expected to run in 35°C weather.
CFD analysis would be done on the batteries assuming 106 Watts of heat generation to simulate
the loads that would be faced during the autocross and endurance events. A steady state analysis was
done because it was faster to simulate and transient CFD attempts appeared to show that the batteries
reached steady state before 30 minutes. The program used to perform the CFD analysis was SolidWorks
Flow Simulation 2011. Air flow through one battery pack was simulated. Each battery pack had an
opening on the top and bottom that was covered in paper with 12 holes punched out of the paper to allow
for air flow. An initial CFD analysis, assuming air flow through the small holes in the paper, showed a

6
great pressure drop and significant temperature rises, thus it was determined that to get any amount of
decent air flow through the battery packs, the paper coverings on the top and bottom of the packs would
have to be removed. Simulation also took much longer to do using the small holes in the paper for air to
have to flow through. All simulation thereafter was thus done assuming the paper was removed.
The results of the CFD analysis can be seen in Table 1.
According to the CFD analysis, each pack would need about 20 CFM of air flow to keep it at
around 50°C. At that flow rate, there would be a pressure drop through the battery pack of around 50 Pa.
Figure 2 shows the temperature rise curve for 35°C air flowing through 1 battery pack.
FIGURE 2: MAX TEMPERATURE RISE OF 18650 CELLS DUE TO AIR FLOW
THROUGH 1 BATTERY PACK
5, 79.33
10, 60.33
20, 50.56
40, 45.18
80, 41.61 120, 40.14
35
40
45
50
55
60
65
70
75
80
85
0 20 40 60 80 100 120 140
MaxCellTemp(°C)
Volumetric Flow Rate (CFM)
Max Cell Temp vs. CFM
20 CFM = Minimum air
flow needed for 1 pack
40 CFM = Most efficient
air flow usage for 1 pack
TABLE 1: BATTERY CFD ANALYSIS
Battery Pack (Test #4) - Without Holes
iR=.195Ω ; Cp=.925J/g∙K ; 106W
Volumetric Flow Rate (cfm) Ambient In Max Min Max Min (Exit) Max (Entrance) ΔP Min Max
5 35 79.32 59.9 79.33 101324.7 101328.9 4 0 3.077
10 34.97 60.31 49 60.33 101323.5 101337.43 14 0 6.203
20 35 50.54 43.9 50.56 101318.9 101369.39 50 0 12.467
40 34.99 45.15 41 45.18 101300.7 101493.22 193 0 24.645
80 34.98 41.58 38.9 41.61 101225.2 101974.12 749 0 49.013
120 34.77 40.1 38 40.14 101099.8 102773.33 1674 0
Air Temp (°C) Cell Temp (°C) Pressure (Pa) Air Velocity (mph)

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As can be seen from Figure 2, the temperature initially drops dramatically as CFM increases.
Eventually this curve levels out and increasing the amount of air flow through the battery pack begins to
have very little effect on lowering the temperature any further. According to the graph, 40 CFM of air
flow appears to be the most efficient use of air flow in lowering the temperature of the batteries. Any air
flow greater than 40 CFM would have less and less effect on the internal temperature of the battery pack.
Thus, finding a fan that could produce 40 CFM through each battery pack would be ideal, but only 20
CFM was necessary.
Figure 3 shows the drop in pressure curve for air flowing through 1 battery pack.
The arrangement of the battery packs on the vehicle was such that air flow would be channeled
through 2 battery packs on the right hand side of the vehicle and 2 battery packs on the left hand side.
Thus, the amount of airflow needed to flow through any one side of the vehicle would have to be
sufficient to cool 2 battery packs. This meant that a fan would be needed that could produce double the
CFM needed for one battery. The pressure drop, however, should remain relatively similar to that needed
for just one pack. Knowing this, a load curve was created from the CFD analysis where the CFM data
was doubled, but the ΔP data remained the same. A fan would have to be found that could handle this
load curve. This altered load curve can be seen in Figure 4.
FIGURE 3: PRESSURE DROP DUE TO AIR FLOW
THROUGH 1 BATTERY PACK
5, 4 10, 14
20, 50
40, 193
80, 746
120, 1672
0
200
400
600
800
1000
1200
1400
1600
1800
0 20 40 60 80 100 120 140
ΔP(Pa)
ΔP vs. CFM (1 Battery Pack)
flow needed for 1 pack
40 CFM = Most efficient air
flow usage for 1 pack

8
Fan performance curves were analyzed to find one that could efficiently handle this load curve.
To do so, one had to know where the load curve should lie on the fan performance curve. Figure 5
provides a simple example for the ideal positioning of a load curve on a fan performance curve.
FIGURE 4: PRESSURE DROP DUE TO AIR FLOW
THROUGH 2 BATTERY PACKS
10, 4 20, 15
40, 52
80, 195
160, 750
0
200
400
600
800
1000
1200
0 60 120 180 240
ΔP vs. CFM (2 Battery Packs)
ΔP
(Pa)
40 CFM = Minimum air flow
needed for 2 packs
80 CFM = Most efficient
air flow usage for 2 packs
FIGURE 5: OPERATION RANGE FOR A FAN
S O U R C E : E B MP AP S T [ 1 0 ]

9
A fan was found that could provide the cooling necessary for our battery packs. It was a Sanyo
Denki San Ace 60 axial fan, model #9GV0612P1G03. Its 100% PWM duty performance curve [18] is
plotted with the battery load curve in Figure 6. The fan would allow for further pressure drop than was
needed to get through the battery packs themselves to allow for a filter and air travel through ducting
leading to and away from the battery packs. It also should allow for ambient temperatures a little bit
higher than 35°C (95°F).
Once a fan was selected, a ducting and housing system had to be designed to channel the air into
the battery packs and out again. Appendix 1 shows depictions describing the battery ducting, housing,
and channeling of airflow design.
B O O S T C A P A C I T O R S
The Maxwell BCAP3000 boost capacitors that would be used to accumulate the energy generated
by our electric motor during breaking also needed to be analyzed for heat generation.
FIGURE 6: FAN PERFORMANCE AND BATTERY LOAD CURVES
10, 4 20, 15
40, 52
80, 195
0
100
200
300
400
500
600
700
800
900
0 10 20 30 40 50 60 70 80 90 100
San Ace 60 Performance vs Battery Load Curves
Battery Load Curve
San Ace 60 Performance Curve
ΔP
(Pa)
flow needed for 2 packs
80 CFM = Most efficient air flow usage for 2 packs
• Not necessary to achieve
• Would have to resort to a much more
expensive and power consuming fan to achieve

10
The first thing to do was to determine the load that the boost caps would be placed under. Our
team’s control system engineer, Patrick Donovan, stated that during breaking, the boost caps could be
charged up to about 200amps. The 14 boost caps mounted in series would charge up during breaking, but
shouldn’t exceed 28 volts. Once the caps received a charge, they would automatically discharge through
the DC-DC’s into the batteries or back into the motor until the caps reached about 10.5 volts. At this
point, discharging of the caps would cease and charging through regenerative breaking would begin
again. During discharge, the caps were unlikely to go above 200amps either. Discharging was estimated
to last about 8 seconds. The conservative assumption was taken that 200amps would either be entering or
leaving the caps with a 50% duty cycle during the autocross and endurance events. The caps were not
used during static charging of the batteries and were to be used only briefly during the sprint events.
Thus, the loads during these events were not considered in this analysis of the boost caps.
The next step was to determine the loads and temperatures that the boost capacitors could
withstand. According their data sheet, the maximum continuous RMS current that the caps were rated to
withstand was 210amps [15]. Their maximum operating temperature was 65°C [15].
The amount of heat that each boost cap would generate was estimated using data from the
National Renewable Energy Laboratory. This is a national laboratory of the U.S. Department of Energy,
Office of Energy Efficiency & Renewable Energy. They performed a number of heat generation tests on
the exact same boost caps that we were using: Maxwell BCAP3000’s. Figure 7 provides a good summary
of their test results for heat generation.
According to their testing results, each boost cap generates about 14 watts of heat at 200amps
RMS [13]. During our usage it may be possible to charge the caps up to 300 amps intermittently, but we
shouldn’t go over 200amps normally.
FIGURE 7: CALORIMETER RESULTS: HEAT GENERATION & EFFICIENCY
S O U R C E : N AT I O N A L R E N E W A B LE E N E R G Y L A B O R A T O R Y [ 1 3 ]

11
The fourth step was to determine how hot the boost caps would get during the assumed loads and
load times. According to the same study by the National Renewable Energy Laboratory, the equivalent
internal resistance of each boost cap at 200 amps RMS was 0.000350 Ω, the specific heat of each cap was
measured to be 1.0796 J/g·K, and the mass of each cap measured to be 545 grams [13]. Again, equation 2
was used to estimate the amount of temperature rise would occur in each cap assuming a worst case
scenario, fully insulated situation. Given a 200amp load with a 50% duty cycle, the caps would have a
temperature rise of 21.4°C after 30 minutes. This was perfectly fine given the maximum temperature
allowance of 65°C and that we were designing for a 35° - 40°C ambient temperature. These results
agreed perfectly with further results presented by the National Renewable Energy Laboratory’s testing.
According to calculations, the boost caps should be able to stay below their 65°C allowance up to a 70%
duty cycle, assuming a 35°C ambient temperature and no cooling whatsoever to the caps. A 100% duty
cycle could probably be achieved if natural convection was allowed.
Research, calculations, and testing data confirm that even given conservative load assumptions,
no forced cooling will be necessary for the boost capacitors. Depictions of the housing design can be
seen in Appendix 2.
D C - D C C O N V E R T E R S
The DC-DC converters convert a varying input voltage into a constant output voltage. The DC-
DC’s will be used in our regenerative braking system to charge the batteries and return power to the drive
train while the vehicle is in use. They will also be used to recharge the battery packs between events
when the vehicle is not in use. 20 DC-DC’s connected in parallel will be used. Each DC-DC has a
maximum output power of 150W [1]. Each DC-DC also has two sets of aluminum fins, as can be seen in
Figure 8, to help dissipate heat. The manufacturer recommends forced convection cooling when the DC-
DC’s are transferring more than 100W through them [1]. The manufacturer also lists a maximum
temperature of 85°C that can be tolerated [1]. Of the three electrical components being analyzed for this
project, the DC-DC’s were the most difficult to estimate heat generation due to the complex nature of
their usage.
FIGURE 8: 150W DC-DC 10-32V TO 12-35V
CONVERTER BOOST CHARGER
S O U R C E : W W W . S AT I S T R O N I C S . C O M [ 1 ]

12
When the vehicle is in use, the regenerative braking system will be active. During braking, the
electric motor will be used as a generator to both slow the vehicle down and charge up the boost caps.
The voltage coming from the motor will be roughly whatever voltage the current state of the batteries is
at. This may vary from 29V when the battery packs are fully charged to 24V when the packs are fully
discharged. The caps can never charge up above the voltage coming from the motor. The current coming
from the motor will vary depending on how hard the brakes are applied and how fast the vehicle is
moving. It may vary from 60 – 300amps. Each time the brakes are applied, the boost caps will receive a
charge. As soon as the brakes are disengaged and capacitor charging ceases, the boost caps will
immediately discharge whatever charge they obtained through the DC-DC’s into the batteries or drive
train. The input voltage into the DC-DC’s will be whatever the voltage of the boost capacitors are and
can vary from 28V to 10.5V. As the boost caps discharge, their voltage will decrease until they are fully
discharged to 10.5V. The output voltage will be a constant 29.5V.
The input current into the DC-DC’s will vary depending on the input voltage of the caps. The
max current that can pass though each DC-DC at an input voltage of 28V is 5.36amps. This agrees with
the 150W power limit per DC-DC [1]. The efficiency of the DC-DC’s with this input voltage is estimated
to be around 94% according to manufacturer’s data [1]. Given this efficiency and these conditions, each
DC-DC should generate about 9W of heat. The max current that can pass through each DC-DC at an
input voltage of 10.5V is 14.29amps. The efficiency of the DC-DC’s with this input voltage is estimated
to be around 83% according to testing results. Given this efficiency and these conditions, each DC-DC
should generate about 25.5W of heat. Thus, the higher the input voltage, the lower the efficiency is of the
DC-DC’s and the less heat they will generate. The cause of this heat generation or change in efficiency is
not so much the input voltage, but rather the difference between the input and output voltages. The
greater the difference, the lower the efficiency.
During static charging of the battery packs when the vehicle is not in use, a 12V charger will be
placed on the input side of the DC-DC’s and will input a current of 60amps to the DC-DC assembly. The
output voltage of the DC-DC assembly will be 30V with an estimated output current of 20.68amps. An
85% efficiency was estimated for these calculations. This calculates to a heat generation of 5.4W per
DC-DC. Charging is estimated to take about 2 hours.
The most heat generation would occur while the vehicle is in use and regenerative braking is
occurring. If the most amount of energy possible were to pass though the DC-DC’s while the boost caps
discharged, which would be ideal, then the heat generation of each DC-DC would increase from 9W to
25.5W from start to end of discharge respectively. This comes to an average of 17.25W of heat
generation during discharge. Discharging is estimated to take between 8 -10 seconds. How often the
boost caps will be discharging is unsure as the layout of the track is unknown. Track layouts from past
years have had numerous corners within them, which would translate to routine braking. Worst case
scenario would be that the caps would be continuously charging and discharging. While the caps are
charging, no current is flowing through the DC-DC’s, however, the caps can charge much more quickly
than they can discharge through the DC-DC’s. Thus, assuming constant charging and discharging with
90% of this time being spent discharging, a heat generation of 15.6W per DC-DC was assumed for CFD
analysis.
The team requested a housing design that was not big and bulky and would take up as little room
possible. To achieve this, a flat design was approached where the DC-DC’s would be arranged into two
rows of 10 DC-DC’s. Playing with a number of different housing designs, one was finally chosen that
would produce the most amount of cooling. This design consisted of each row of DC-DC’s being housed

13
within its own air channel having its own fan. All wires would be routed to a conjoining channel between
each row of DC-DC’s. This wire channel would be walled off from the DC-DC channels so that all air
flow could be directed over the fins of the DC-DC and none would be lost going to the wires. The cross-
sectional layout can be seen in Figure 9.
The results of the CFD analysis for the DC-DC’s can be seen in Table 2, Figure 10, and Figure 11
below. Table 2 displays the actual data results from the analysis. Figure 10 displays the max DC-DC
temperature vs. airflow curve and, while Figure 11 shows the load curve produced due to the pressure
drop through the DC-DC’s air duct.
FIGURE 9: CROSS-SECTIONAL VIEW OF DC-DC
HOUSING LAYOUT
S O U R C E : D C - D C H O U S I N G AS S E M B LY # 3
TABLE 2: DC-DC CFD ANALYSIS
S O U R C E : D C - D C C F D AN A L Y S I S # 3
Total Needed Half Assembly (10 DC-DC's) Ambient In Max Min Max Min Max ΔP Min Max (Entrance) ΔP Min Max
20 10 34.81 130.8 76.9 130.8 101324.91 101332.92 8 101324.91 101332.03 7 0 7.788
40 20 34.98 97.16 63.5 97.16 101324.74 101353.54 29 101324.74 101350.34 26 0 14.782
60 30 34.96 81.63 57.5 81.63 101324.46 101387.73 63 101324.46 101380.7 56 0 21.87
80 40 34.95 73.89 53.9 73.89 101324.07 101434.63 111 101324.07 101422.35 98 0 28.743
120 60 34.89 65.38 49.7 65.38 101322.84 101567.01 244 101322.84 101539.88 217 0 42.483
160 80 34.8 60.8 47.3 60.8 101320.9 101751.25 430 101320.9 101703.44 383 0 56.405
Pressure (Pa) Air Velocity (mph)Volumetric Flow Rate (cfm) Air Temp (°C) DC-DC Temp (°C) Pressure (Pa)

14
A fan needed to be selected that could produce the airflow necessary to keep the DC-DC’s below
85°C, as well as the necessary performance needed for the load curve in Figure 11. A Sanyo Denko San
Ace 60 axial fan, model #9GV0612P1H03, was chosen. This was one very similar to the one selected for
the battery pack cooling with the only difference being that this one had a slightly less powerful motor.
Its 100% PWM duty performance curve [18] is plotted with the DC-DC load curve in Figure 12.
FIGURE 10: MAX TEMPERATURE RISE OF DC-DC’S DUE TO
AIR FLOW OVER 1 ROW OF 10 DC-DC’S
10, 130.8
20, 97.16
30, 81.63
40, 73.89
60, 65.38
80, 60.8
35
55
75
95
115
135
155
0 20 40 60 80 100
MaxCellTemp(°C)
Max DC-DC Temp vs. CFM
FIGURE 11: PRESSURE DROP DUE TO
AIR FLOW OVER 1 ROW OF 10 DC-DC’S
10, 8
20, 29
30, 63
40, 111
60, 244
80, 430
0
50
100
150
200
250
300
350
400
450
500
0 20 40 60 80 100
ΔP(Pa)
ΔP vs. CFM
Analysis #3: Max ΔP

15
About 30 CFM is necessary to keep the highest temperature of the hottest DC-DC below 85°C,
however, there is a 24°C difference between the warmest and coolest DC-DC with this air flow. Patrick
was worried that this temperature differential may affect the performance of the DC-DC’s. To bring this
temperature difference down, more air flow would be needed. According to Table 2, 60 CFM would
reduce this difference to 15°C. Thus, more than 30 CFM would be desired under these loading
conditions. This fan is able to produce more than 30 CFM, probably between 50 – 60 CFM, assuming the
slope of the load curve will rise due to the addition of filers on either end to prevent water and debris from
entering the housing. Two of these fans will be used, one to cool each row of DC-DC’s.
Depictions of the housing design and can be seen in Appendix 3.
M E 4 2 7 T H E R M A L D E S I G N C L A S S I N V O L V E M E N T
To involve Dr. Shih’s two thermal design classes in this project, I presented the project as a
company representative from FHSAE. Grant Feenstra, our team’s design captain for 2011-2012,
happened to also be in one of these thermal design classes. Due to his involvement with the team, he was
unable to be included on one of the design teams in the class. Thus, Dr. Shih made Grant a co-
representative of the team. Together, he and I acted as team representatives and general engineering
managers. We presented the project to them, gave students tours of our lab and our car, answered
FIGURE 12: FAN PERFORMANCE AND DC-DC LOAD CURVES
10, 8
20, 29
30, 63
40, 111
60, 244
80, 430
0
100
200
300
400
500
600
700
0 20 40 60 80 100
ΔP(Pa)
San Ace 60 Performance vs DC-DC Load Curve
Analysis #3: Half Duct
San Ace 60
(#9GV0612P1H03)

16
questions for them, and sat in on design reviews and critiqued their designs. To start, we introduced the
students to our “company”, how our car and its electrical systems operate, and ultimately to our need for
an electronic cooling system.
Provided to the students were:
1) Makes and models of the electrical equipment
2) Detailed SolidWorks models of the electrical equipment
3) SolidWorks models of selected portions of the 2012 FHSAE car including its frame, internal
combustion engine, seat, radiator, and extra 12V battery
4) Estimated peak and normal operational loads of electrical equipment
5) Access to our lab during FHSAE build days to get better visual and hands-on exposure to the
project and the team in general
6) Anything else deemed necessary by Dr. Shih or the students to complete the project
Desired outcomes of this project were:
1) Documentation of necessary equipment needed to supply adequate cooling to the system (i.e.
fans, insulating materials, design and makeup of electronic housings, additional fins, coolant,
piping, heat sinks, cold plates, etc.)
2) Documentation of design layout within the car, including positioning of all electrical/electronic
equipment and additional cooling components (visual SolidWorks representation desired)
3) Documentation of all assumptions and calculations used to arrive at final design
4) All costs associated with the cooling system
5) Final written report presenting all of the above
6) Oral presentation of design to FHSAE representatives
Periodic visits to the class could be arranged to check up on student progress, answer questions,
and present updated information, however, students failed to take advantage of this. One possibility could
have been that they were afraid of my $500/hour charge. Or perhaps they never got organized enough to
know what to ask. I did come in one day, of my own accord, to try and jump start them into beginning
the project. I did a short lecture on general heat transfer calculations.
Three design reviews were assigned to the thermal design classes, the first being an initial design
review on the Wednesday of week 6. The second was a critical design review on the Wednesday and
Friday of week 8. The third was a final design review on the Wednesday and Friday of week 10.
The first design review, for the most part, showed that not a whole lot of work had been done by
any of the groups. Very few, if any, calculations had been done and little to no SolidWorks modeling had
been done. It was obvious that the individual teams within each group were not communicating well
because everyone seemed to want to place their electronics in the same location: behind the driver’s seat.
The second design review showed a great amount of improvement. Many more calculations had
been done as well as more SolidWorks modeling. Still, only about half the groups showed a vehicle
frame with each team’s components placed within it. Communication between teams was improving, but
still inadequate. There was still very little presented, design-wise, that could have really been of any
actual use on our vehicle.

17
The third design review showed a great amount of improvement in communication between
teams within each group. Designs were coming together so that each of the different components had its
own location on the vehicle. The heat shield teams had the simplest task and were probably the only
teams that came up with something by the final design review that would actually work and could
actually be used. None of the capacitor teams came to the conclusion that no cooling would be needed for
them. Every team had some sort of forced convection cooling for them. DC-DC converter teams, for the
most part, presented designs that might work, but that were impractical or unusable for our particular
application. Battery teams had trouble initially determining how much heat the battery packs would
actually be generating along with their duty cycles, etc. The 200amp average and 400amp peak loads
they were initially presented with posed the same two problems I was initially faced with. First, that the
batteries were not even rated to be run above 200amps and so these loads could not be achieved safely.
Second, the amount of heat being generated by the batteries at 200amps was astronomical. By the final
review only one team had figured out these problems on their own and asked me to lower the loads.
Another team had been on the verge of figuring it out and, after some pushing by myself, they too asked if
they could lower the amperages. No battery team, by the final review, had come up with a full usable
design for cooling the batteries.
A common problem seen in all designs (not including the heat shield) was the lack of concern for
keeping the electrical components protected from rainy conditions. Another problem was determining
pressure drops and finding adequate fans to compensate for these pressure drops. Little to no CFD
analysis was done by any of the teams.
C O N C L U S I O N
This report, for the most part, only provides a brief description of the final calculations,
assumptions, and designs for this project. It only scratches the surface in describing all the work that was
actually done in research, initial designs, early CFD analyses, and testing to arrive at the final design.
This truly felt like a real life engineering project (as it should have because it was). A large set of
rules, regulations, and design criteria had to be met and followed. The final design had to work with the
designs of other people on the team. The exhaust had to be routed in such a way so that it didn’t get too
close to the battery packs. The aero team’s side body ducts had to be slightly reshaped to accommodate
the DC-DC housing, which would be placed on the outer right side of the vehicle. The battery packs,
boost caps, and DC-DC’s all had instances where they had to be redesigned and moved around because
the team president and/or design captain didn’t like the way they looked or how their placing might affect
the handling and performance of the vehicle. Much arguing, reasoning, and communication occurred
between Patrick, our controls and drive train engineer, and I because he had his own ideas of how things
should be housed, placed, and mounted. My design had to work with the way he was setting things up.
His job was to make sure everything worked; my job was to make sure everything kept working, safely.
Sometimes our goals did not agree with each other. In the end, everyone was happy and satisfied with my
design.
I received help from a number of different people throughout the course of this project. Travis
Feenstra, an electronics cooling engineer at Raytheon, helped me with a number of things. He showed me

18
how to do my CFD analysis, gave me design ideas, showed me some good websites to find information
and parts, and critiqued my designs. I found an electrical engineering senior, William Smit, to create the
PWM controller for my fans. The thermal design classes provided me with two major items: ideas for our
heat shield and the research performed by the National Renewable Energy Laboratory on our boost
capacitors [13]. Dr. Angela Shih was my advisor for this project and I am very thankful to her for
providing me the opportunity to do this project alongside her thermal design classes. She provided me
with insight from her experience as a thermal engineer, gave me ideas, and critiqued my designs.
I know I learned a lot from this senior project. The knowledge gained from it can be very
beneficial as electronic cooling is becoming more and more important in today’s industry. Electronics are
continually getting smaller and more powerful, producing more heat with less surface area to work with.
Electronic cooling engineers are in demand for this reason. Perhaps, with the experience gained from this
project, I may be able to secure one of these jobs.
I have been a member of the Cal Poly FHSAE team for 3 years now, since its first year in
existence at this school. It has been an exciting experience and I am happy to have been able to help in
the design of our third and hopefully best car to date. The next step in this project is to actually build
everything, which has already begun, and watch it all work!

19
R E F E R E N C E S
[1] "150W DC-DC 10-32V to 12-35V Converter Boost Charger." Satistronics. Satistronics Store,
2012. Web. 16 Mar 2012. <http://www.satistronics.com/150w-dcdc-1032v-to-1235v-converter-
boost-charger_p2985.html>.
[2] "18650 battery test 2011." Velkommen til min side om lygter. N.p., n.d. Web. 15 Mar 2012.
<http://lygte-info.dk/info/Batteries18650-2011 UK.html>.
[3] "2012 Formula Hybrid Rules." Formula Hybrid International Competition. 2011 SAE
International, 25 Aug 2011. Web. 16 Mar 2012. <http://www.formula-hybrid.org/pdf/Formula-
Hybrid-2012-Rules.pdf>.
[4] Allan, Joshua. "Battery data sheets." Message to Daniel Miersma. 06 Feb 2012. E-mail.
[5] Allan, Joshua. "Re: Battery data sheets." Message to Daniel Miersma. 09 Feb 2012. E-mail.
[6] Allan, Joshua. "Re: 18650 data sheet." Message to Mike Schantz. 17 Jan 2012. E-mail.
[7] Allan, Joshua. Telephone Interview. Feb 2012.
[8] "Battery Performance Characteristics." The Electropaedia. Woodbank Communications Ltd., n.d.
Web. 23 Nov 2011. <http://www.mpoweruk.com/performance.htm>.
[9] "Battery Testing." The Electropaedia. Woodbank Communications Ltd., n.d. Web. 23 Nov 2011.
<http://www.mpoweruk.com/testing.htm>.
[10] "Compact fans for AC and DC." ebmpapst: the engineer’s choice. ebmpapst, n.d. Web. 16 Mar
2012. <http://www.ebmpapst.com/media/content/info-
center/downloads_10/catalogs/compactfansen2011/Compact_fans_for_AC_and_DC__2011.pdf>.
[11] Gao, Lijun. "Dynamic Lithium-Ion Battery Model for System Simulation." IEEE
TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES. 25.3 (2002): 495-
505. Web. 15 Mar. 2012.
<http://vtb.engr.sc.edu/vtbwebsite/downloads/publications/LithiunIonBattery_Lius.pdf>.
[12] Incropera, Frank. Introduction to Heat Transfer. 5th ed. Hoboken: John Wiley & Sons, Inc.,
2007. Print.

20
[13] Lustbader, Jason. "Thermal Evaluation of a High-Voltage Ultracapacitor Module for Vehicle
Applications." www.nrel.gov. National Renewable Energy Laboratory, 15 Jul 2008. Web. 16 Mar
2012. <http://www.nrel.gov/vehiclesandfuels/energystorage/pdfs/43564.pdf>.
[14] Jhu, C.-Y. "Self-reactive rating of thermal runaway hazards on 18650 lithium-ion batteries."
Journal of Thermal Analysis and Calorimetry. (2011): 159-163. Print.
[15] "K2 Series Ultracapacitors." maxwell.com. Maxwell Technologies, n.d. Web. 16 Mar 2012.
<http://www.maxwell.com/products/ultracapacitors/docs/datasheet_k2_series_1015370.pdf>.
[16] "Lithium-Ion Battery Pack Recommendations." AC Propulsion, Print.
[17] "Lithium-Ion Presentation." swe.com. SOUTHWEST ELECTRONIC ENERGY GROUP, n.d.
Web. 15 Mar 2012.
[18] "San Ace 60." www.sanyodenki.com. Sanyo Denki, n.d. Web. 16 Mar 2012.
<http://db.sanyodenki.co.jp/product_db/cooling/dcfan/group_pdf/1268713397.pdf>.
[19] "Thermal Management." The Electropaedia. Woodbank Communications Ltd., n.d. Web. 23 Nov
2011. <http://www.mpoweruk.com/thermal.htm>.

21
A P P E N D I X 1 – B A T T E R Y D E S I G N D E P I C T I O N S
FIGURE A1-1: FAN, FILTER, AND SHROUD ASSEMBLY
FIGURE A1-2: FAN, FILTER, AND SHROUD ASSEMBLY
(EXPLODED VIEW)
FIGURE A1-3: BATTERY DUCT ASSEMBLY
(LEFT SIDE)

22
FIGURE A1-4: BATTERY, DUCT, & BOX ASSEMBLY
(TOP-LEFT VIEW)
FIGURE A1-5: BATTERY, DUCT, & BOX ASSEMBLY
(BOTTOM-LEFT VIEW)

23
A P P E N D I X 2 – B O O S T C A P A C I T O R D E S I G N D E P I C T I O N S
FIGURE A2-1: CAPACITOR FACE PLATE
(CNC’D POLYCARBONATE)
FIGURE A2-2: CAPACITOR & FACE PLATE ASSEMBLY

24
FIGURE A2-3: CAPACITOR, FACE PLATE, & BOX ASSEMBLY

25
A P P E N D I X 3 – D C - D C C O N V E R T E R D E S I G N D E P I C T I O N S
FIGURE A3-1: DC-DC ASSEMBLY (STEP 1)

26

27

28
A P P E N D I X 4 – F U L L V E H I C L E D E S I G N D E P I C T I O N S
FIGURE A4-2: FRAME & ELECTRICAL TOP VIEW
FIGURE A4-1: FRAME & ELECTRICAL LEFT SIDE VIEW

29
FIGURE A4-3: FRAME & ELECTRICAL PHOTO RENDERING #1
FIGURE A4-4: FRAME & ELECTRICAL PHOTO RENDERING #2

30
FIGURE A4-5: PHOTO RENDERING OF VEHICLE
(WITHOUT CAPACITORS OR AERO SIDE PODS)
FIGURE A4-6: OFFICIAL PHOTO RENDERING OF VEHICLE

31
B I L L O F M A T E R I A L S
Item Use Seller Cost/unit Quantity Total Cost
1/8" Polycarbonate Welding Rod Plastic Welding McMaster $32.65/1 lb coil 1 $32.65
Adhesive back Foam Striping Water & Air seal containers McMaster $9.31/50' coil 1 $9.31
EMI/RFI 60mm fan filter DC-DC housing filter McMaster $5.37 2 $10.74
EMI/RFI 60mm fan filter DC-DC housing filter Newark.com $3.04 2 $6.08
EMI/RFI 120mm fan filter Battery duct filter Newark.com $3.92 2 $7.84
San Ace 60 fan (#9GV0612P1G03) Battery cooling Newark.com $26.21 2 $52.42
San Ace 60 fan (#9GV0612P1H03) DC-DC cooling Newark.com $19.98 2 $39.96
1/8" Polycarbonate Sheet Make housings Orange County Industrial Plastics $84/(8'x4'x1/8") sheet 1 $84
Fiberglass Forming Material Make battery ducts Cal Poly Pomona FSAE donated N/A N/A
Plastic CNC Capacitor housing So Cal Teardrops donated N/A N/A
Foam CNC Battery ducts Cal Poly SLO donated N/A N/A
Tax/Shipping/Handling - - - - $24.56
Miscellaneous - - - - $100
Total: $367.56

32
S A M P L E C A L C U L A T I O N S
𝐻𝑒𝑎𝑡 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 (𝑝𝑒𝑟 18650 𝑐𝑒𝑙𝑙) = 𝐼2
𝑅 = (
120𝑎𝑚𝑝𝑠
53 𝑐𝑒𝑙𝑙𝑠
)
2
0.195Ω = 0.9996 𝑊𝑎𝑡𝑡𝑠
𝐻𝑒𝑎𝑡 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 (𝑝𝑒𝑟 𝑏𝑎𝑡𝑡𝑒𝑟𝑦 𝑝𝑎𝑐𝑘) = (ℎ𝑒𝑎𝑡 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛/𝑐𝑒𝑙𝑙) 𝑥 (106 𝑐𝑒𝑙𝑙𝑠/𝑝𝑎𝑐𝑘)
= (0.9996 𝑊𝑎𝑡𝑡𝑠/𝑐𝑒𝑙𝑙) 𝑥 (106 𝑐𝑒𝑙𝑙𝑠/𝑝𝑎𝑐𝑘) = 106 𝑊𝑎𝑡𝑡𝑠
𝑇𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 𝑟𝑖𝑠𝑒 𝑜𝑓 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 𝑖𝑛 30 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 (∆𝑇) =
𝐼2
𝑅 ∙ 𝑡
𝑚 ∙ 𝐶 𝑝
=
(ℎ𝑒𝑎𝑡 𝑔𝑒𝑛𝑒𝑎𝑟𝑎𝑡𝑖𝑜𝑛/𝑐𝑒𝑙𝑙) ∙ (𝑡𝑖𝑚𝑒)
(𝑚𝑎𝑠𝑠/𝑐𝑒𝑙𝑙) ∙ (𝑠𝑝𝑒𝑐𝑖𝑓𝑖𝑐 ℎ𝑒𝑎𝑡)
=
0.9996 𝑊𝑎𝑡𝑡𝑠 ∙ 1800 𝑠𝑒𝑐𝑜𝑛𝑑𝑠
45 𝑔𝑟𝑎𝑚𝑠 ∙ 0.925 𝐽/𝑔 ∙ 𝐾
= 43.2℃
𝐻𝑒𝑎𝑡 𝐺𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛 𝑜𝑓 𝑏𝑎𝑡𝑡𝑒𝑟𝑖𝑒𝑠 𝑤𝑖𝑡ℎ 150 𝑎𝑚𝑝 𝑙𝑜𝑎𝑑 𝑎𝑛𝑑 65% 𝑑𝑢𝑡𝑦 𝑐𝑦𝑐𝑙𝑒
= (ℎ𝑒𝑎𝑡 𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑖𝑜𝑛/𝑝𝑎𝑐𝑘) 𝑥 0.65 = 165.6 𝑊𝑎𝑡𝑡𝑠 ∙ 0.65 = 107.6 𝑊𝑎𝑡𝑡𝑠
𝐷𝐶 − 𝐷𝐶 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 =
𝑝𝑜𝑤𝑒𝑟 𝑖𝑛
𝑝𝑜𝑤𝑒𝑟 𝑜𝑢𝑡
=
(𝑉𝐼)𝑖𝑛
(𝑉𝐼) 𝑜𝑢𝑡
=
[(10.5𝑉) ∙ (12.4𝑎𝑚𝑝𝑠)]𝑖𝑛
[(29.5𝑉) ∙ (3.7𝑎𝑚𝑝𝑠)] 𝑜𝑢𝑡
=
130 𝑊𝑎𝑡𝑡𝑠
108 𝑊𝑎𝑡𝑡𝑠
= 0.83

Daniel Miersma's Senior Project Final Report

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