This document describes a proposed design for an electric vehicle that uses both a lithium-ion battery and a zinc-air battery to increase the vehicle's driving range. The lithium-ion battery is used for most daily driving needs while the zinc-air battery extends the vehicle's total range to over 500 km on a single charge. Simulation results showed the design could meet a typical suburban driver's daily needs of 59 km using just the lithium-ion battery in 94% of cases. When more range is needed, the zinc-air battery provides additional energy capacity. The design aims to eliminate the need for rapid charging by using overnight charging.

1. DESIGN OF RANGE EXTENDING DUAL ENERGY
STORAGE SYSTEM FOR AN ELECTRICVEHICLE
Group 9: Nathan Buckley, Julia Helter, Betty Liu, Steven Sherman
Faculty Advisor: Dr. Michael Fowler
ZINC AIR LITHIUM ION
Although most drivers live in the suburbs, battery packs have also been
designed for urban drivers and commuters. By design, 75 - 90% of the time
only the Li-Ion battery will be used, reserving the Zn-Air battery for extended
driving. The battery discharge prioritization allows the Zn-Air to last over 10
years.
Urban: This driver usually travels short distances and thus requires the least
energy. Consequently, this vehicle is lower cost and more fuel efficient, but
has just over half the range of the suburban vehicle.
Suburban: The average driver travels short distances on most days but
sometimes takes long trips. This vehicle requires a mid-sized Li-Ion battery
and large Zn-Air battery to maximize battery life and driving range. The cost
and fuel economy of this vehicle balances between urban and commuter.
Commuter: This user has the highest percentage of long trips and requires
the largest lithium ion battery. This vehicle is less fuel efficient, more
expensive, and has a approximately the same range of the suburban vehicle.
VEHICLE OPTIONS
Vehicle
Li-Ion
Energy
[kWh]
Zn-Air
Energy
[kWh]
Mass
[kg]
Range
[km]
Fuel
Economy
[kWh/100 km]
Battery
Cost
[USD]
Zn-Air
Life
[years]
Urban 13 73 309 340 22.0 $15,700 11.5
Suburban 26 132 581 577 23.7 $29,000 11.9
Commuter 40 117 670 573 25.4 $30,600 16.0
Anode (Graphite): LiC6 ↔ 6C + Li+
+ e–
Cathode (Lithium iron phosphate): LiFePO4 + 6C + e–
↔ LiC6 + FePO4
–
LITHIUM ION BATTERY
CharacteristicsBattery Properties
Nominal Cell Voltage [V] 3.3 High power density
Specific Energy [Wh/Kg] 131 Low energy density
Cost [USD/kWh] $300 High cost
Number of Cycles 3000 High cyclability
The objective is to design a battery system for an electric vehicle that:
1. Travels over 500 km on a single charge
2. Mitigates the need for rapid charging
3. Competes on cost with conventional gas powered vehicles
PROJECT GOALS
MOTIVATION
Electric vehicles (EVs) are a rapidly developing and highly promising
sustainable transportation technology; however, EVs still make up less than
1% of vehicle sales. Significant challenges to their widespread
commercialization include range anxiety, long charging times and high
upfront vehicle costs. Creative solutions to these challenges would reduce
greenhouse gas emissions and revolutionize the consumer vehicle market.
PROPOSED SOLUTION
Li-Ion Lvl1: Zn-Air begins charging Li-Ion at this SOC.
Li-Ion Lvl2: Zn-Air stops charging Li-Ion above this SOC.
Zn-Air Min: Zn-Air shuts down at this SOC to avoid battery damage.
Li-Ion Min: Li-Ion shuts down at this SOC to avoid battery damage if Zn-Air
cannot recharge it.
MODEL BASED DESIGN CONTROL LOGIC
Anode (Zinc) : Zn + 4OH−
↔ Zn(OH)4
2−
+ 2e−
Cathode (Oxygen) : ½O2 + H2O + 2e−
↔ 2OH−
ZINC AIR BATTERY
CharacteristicsBattery Properties
Nominal Cell Voltage [V] 1.2 Low power density
Specific Energy [Wh/Kg] 500 High energy density
Cost [USD/kWh] $160 Low cost
Number of Cycles 200 Low cyclability
SUBURBAN VEHICLE FACTORIAL DESIGN
A factorial design was
used to find the optimal
battery sizes. Increasing
Li-Ion and Zn-Air energy
leads to an increase in
range and battery
lifetime, at the expense
of lower efficiencies and
higher battery cost. For
the suburban driver, a
26 kWh Li-Ion battery
and a 132 kWh Zn-Air
battery finds the best
balance between design
factors.
In order to design for driver needs, driver behaviour must be considered. A
typical suburban driver travels an average of 59 km a day. However, 57% of
daily driven distances are below 50 km, and only 15% are above 100 km a day.
DRIVER BEHAVIOR
In order to achieve both
acceptable range and
lifetime of the battery
system, the Li-Ion battery
must be sized to satisfy
the range requirements
on most days, and the Zn-
Air battery sized to
achieve desired range on
longer journeys.
Using two battery technologies and advanced control logic, the project
vehicle:
1. Travels farther than any commercial EV on the market on a single charge
2. Requires only overnight and weekend charging - never rapid charging
3. Competes on cost with other EVs and traditional gas vehicles
Further advances in zinc air battery cycling and cost reductions with
widespread adoption will further improve competitiveness and performance.
CONCLUSIONS
SIMULATION RESULTS
Based on a city driving pattern, the suburban vehicle demonstrates a 94 km
range before the zinc air battery turns on, which is sufficient distance to
satisfy 84% of daily driven distances. This is important in order to prolong
the life of the zinc air battery. At 525 km, the zinc air battery reaches its
minimum SOC and shuts off. The lithium battery has enough charge left to
take the car another 20 km, at which point the car has travelled its full city
driving range of 545 km.
31 2
The project vehicle was compared against a luxury EV and a standard gas-
powered car. The vehicle competes favourably on fuel economy, emissions
and fuel costs with both vehicles, and on range and cost with the EV.
All results are based on combined city and highway driving patterns and off-peak charging. Vehicle
costs do not include government subsidies. Emissions were based off operational usage.
VEHICLE EVALUATIONThe solution combines an energy-
dense zinc air (Zn-Air) battery in series
with a conventional lithium ion (Li-
Ion) battery. The Li-Ion is the primary
power source while the Zn-Air extends
the vehicle’s range.
The state of charge (SOC) shows the
energy level of each battery over an
extended trip. At first, the Li-Ion
powers the car on its own. Once the Li
-Ion becomes partially depleted, the
Zn-Air begins charging the Li-Ion.
When, the Zn-Air becomes depleted,
the Li-Ion continues to power the car
until it too becomes fully depleted.