1. Dawg Sled
University of Washington
What powers our car?
Elon Musk once said that “the problem with existing batteries is
that they suck.” If the CEO of Tesla Motors and SpaceX felt
obligated to complain about batteries and found no dissent from
his complaint, then it is obvious that batteries are the technology
to improve. Currently, the best battery technology is geared
towards lithium-ion batteries. A major problem with building
lithium-ion batteries is the expense. The equipment and
materials needed to build lithium-ion batteries, including the
need for additional safety features, is way over the budget of our
basement laboratory. In the end, we decided upon building a
custom 3-D printed dry cell battery as the energy source of our
car. This dry cell battery is commonly known as the zinc-carbon
battery, but more accurately described as a “zinc-manganese”
battery.
Battery Uniqueness
Although the zinc-carbon battery chemistry is a throwback to the
first commercially sold battery, we had implemented ways to
innovate this classic battery further. The carbon anode used for
this battery is recycled carbon fiber scraps from a materials
science research lab on UW campus. For the battery cell
compartments we employed a customized flat cell design and 3-
D printed the casings in the most efficient manner. After the
battery cell “sandwich” is assembled, each cell are connected in
series and then attached to the electric motor, powering our car.
Materials to make our zinc-carbon battery
Anode (negative terminal)
• Zinc plate
Cathode (positive terminal)
• Manganese dioxide, ammonium chloride, zinc chloride,
graphite powder
• Carbon fiber as the carbon anode
Flat cell compartments (3-D printed)
• PLA (polylactic acid) filament
Zinc-carbon battery total chemical reaction
Zn(s) + 2MnO2(s) + 2NH4Cl(aq) → Mn2O3(s) + Zn(NH3)2Cl2 (aq)
+ H2O(l)
Figure 1: Measuring electric potential of our prototype batteries.
What stops our car?
Iodine Clock
• Hydrogen peroxide variation of the iodine clock reaction to
stop our car.
• After a certain time the color of the solution will change to a
dark blue.
• In order to vary the time we have changed the hydrogen
peroxide concentration.
• The color change blocks light from an LED to a photoresistor,
the voltage change triggers a relay to disconnect the battery
from the motors.
Materials for our iodine clock
Mixture A
•Starch, Sodium thiosulfate, Potassium iodide, Water
Mixture B
•Sulfuric Acid, Hydrogen peroxide, Water
Reaction for the iodine clock
First Reaction
H2O2 + 3I− + 2H+ → I3
- + 2H2O
Generates triiodine ions
Second Reaction
2S2O3
2− + I3
- → S4O6
− + 3I-
This reaction is faster than reaction one and is the rate
determining step.
Third Reaction
I3
- + starch → Starch-I5
- complex + I−
After all the thiosulfate ions have been consumed by reaction 2,
the triiodide ions react with the starch to form the starch-
pentaiodide complex. This product is what gives the solution the
dark blue color.
Environmental, Health, and Safety
• Emission free vehicle!
• Waste is easily disposed of properly to UW EH&S.
• Battery stack is contained within a 3D printed, sealed plastic
casing.
• High pressures, gaseous emissions, and ignition sources are
avoided using the battery system.
• All members wore lab safety goggles and nitrile gloves while
working in the lab.
• Members underwent UW EH&S trainings for managing
laboratory chemicals, fire extinguisher operation and the
Globally Harmonized Systems.
Acknowledgements
The Chem-E-Car Club would like to give thanks to UW Department
of Chemical Engineering for providing us the funds and space to
pursue our project. We would especially like to thank department
chair François Baneyx and our club advisor Professor Stuart Adler.
Figure 2: Initial design of car with 3-D printed body.
Figure 3: The car body group working on assembling the car.
Figure 4: All members of the ChemE Car club, including our advisor
Stuart Adler.