Download Test 2 Results - Senior Design

For Electric Vehicles
Team Members:
Pramit Tamrakar - EE
Jimmy Skadal - EE
Hao Wang - EE
Matthew Schulte - EE
William Zimmerman - EE
Advisor:
Ayman Fayed
Client:
Adan Cervantes
Team-id: SdMay11-04
Problem Statement

To develop an efficient and safe system for charging and monitoring of multicell series batteries in Electric Vehicles using a switching mode power
supply.
Concept Description


Design a Lithium Ion Battery Charger that is capable of safely charging 16
parallel packs of 90 cells in series (Large Scale System).
Successfully build an 18 cell charger that is capable of monitoring and
balancing the cells. (Small Scale System)
Operating Environment
 The large scale product must be able to operate inside an electric
vehicle. Various vibration and temperatures may need to be considered.
However, the scaled down version is a proof of concept, therefore, must
operate in laboratory conditions.
User interface description


The user interface for this scaled down system will be the EVM GUI
that displays the status of the batteries and the switch on the DC power
supply.
For the large scale system, the user will have the EVM GUI display
inside the vehicle and only need to worry about plugging the vehicle in.
Functional Requirements
 Constant-Current Constant-Voltage (CCCV) charging procedure
 Battery Gauging
 Temperature Monitoring
 Under Voltage and Over Voltage Detection
Non-functional Requirements
 Should be usable by our client during the development of the scaled up
version.
 The system should be reliable.
 Ensuring Safety
 The system should be robust and long-lasting.
Charging Goal
 18 Series Batteries, 2.3 Ah each
 45 minute CCCV charge
Market Survey




Commercially available switching mode power
supply for electric vehicles is offered by Brusa.
The NLG5 provides a high voltage power source
from a 120V or 240V wall outlet.
Cost: over $2,000
Brusa does not have a Battery Management
Systems.
NLG503-light battery charger.
1.6 kW 200-540V, $2,145
Deliverables



A presentation giving a general overview of Battery Charging System
A written report detailing:
o Small scaled system
o Overall processes and means by which our system operates
o A summary of the development process
Small scaled prototype
Resource Requirements
Time
 A significant amount of time has been required to complete this project
Money
 $569.24 has been spent on this project
Parts
 Li-ion batteries
 MSP430 microcontrollers
 EVM boards and related software/code
 Inductors, diodes, power transistor, resistors, capacitors, perf boards
and various other circuit equipment
Tools and Lab Access
 Access to soldering equipment, suitable power supply and various other
laboratory equipment
Project Plan
Work breakdown
 Task 1 – Problem Definition
 Task 2 – Acquire a suitable power source
 Task 3 – Boost Converter Design
 Task 4 – bq76PL536EVM-3BMS system design
 Task 5 – Building and Testing
 Task 6 – Documentation and Demonstration
Project Schedule
Risk

Electric Shock: The risk of electric shock is possible when working with a
charging system.

System Component Damage: As power is being applied and the charging
system is running, the risk of overheating, voltage/current spikes, and
incorrect connections are possible.
Mitigation

Testing and Simulation: To prevent component damage and ensure
proper design, the system will be modeled to test for expected results.

Lower Volt System: With the 27V – 60V scaled down system, the risk a
shock is reduced.

Smart and Safe: By knowing how to be safe and building the system with
human/component safety in mind will aid in avoiding risk.
System Requirements
Li-Ion Battery Management




Constant-Current Constant-Voltage
charging procedure
Battery Gauging
Temperature Monitoring
Overcharge Protection
CCCV Charging sequence for
Lithium-Ion Batteries
Functional Decomposition
Large scaled system diagram
Small scaled system diagram
Hardware Specifications
Boost Circuit

Provide the needed voltage or current depending on the %
PWM signal being input into it.
 Must take an input Voltage of 27 VDC and must have an
output of 28.8 – 64.8VDC. (200 Watts Max)
MSP430

Must provide the PWM for the charging cycle.
 Must receive information about the system. voltage/current
and make decisions based on data collected.
 Must track faults
 May be used for cell balancing
Battery Management System


Must collect voltage and temperature data for cell stack.
In conjunction with the Aardvark interface and a PC, it is for
cell balancing
User interface specification

Must tell user when the batteries are charging and also indicate when system is
fully charged.
 Can display voltage of cells for user charging and driving purposes.
Test plan






Test stacked communication of EVMs without cells hooked up.
Test Boost Converter circuit with PWM from signal generator and low voltages.
Hook up small scale voltage and current circuit to test MSP430 code for CCCV.
Test EVMs with Cells connected and ensure PC software can see all devices.
Test Boost Converter with MSP430 PWM control at high voltage/current.
Do a complete system test with discharged cells.
Simulation / prototyping


Used PSpice for initial switching mode power supply design.
Assemble each section of the system and tested
the components in a low voltage and limited current condition.
Implementation/Testing
Boost Converter

Soldered circuit components together on a circuit board
which consist of inductors, capacitors, a Power MOSFET,
a MOSFET Driver, and voltage divider for ADC use.
 Test 1: Low voltage/current (6 VDC & 0 - 1.25A) input and
test PWM control of output with various loads.
 Test 2: Efficiency test of output with various loads.
 Test 3: High voltage/current input (27 VDC & 0 A – 8 A)
with 25 ohm power resistor to simulate battery load.
Test 3 Setup
Test Result



Test 1 Results: Successfully output 6-15 Volts at .01-.5A
at about 80% duty cycle depending on the load.
Test 2 Results: Average 87% (Range of 77% - 99%)
Test 3: Results: Successfully output 65.6 VDC at 3.3 A
with a 61% duty cycle.
Test 1
Test 3 DC Input
Test 2
Test 3 Duty % & Output
Implementation/Testing
Battery Management System



Changed resistors on boards the two boards to configure one
to be in Host Mode and the other in Slave mode.
Test 1: Hooked up each EVM to three DC supplies at 20V. This
test will allow a controlled setting for EVM data communication.
Test 2: This EVM stacking test will show that communication
can be established to all 6 devices while being hooked up to
the 18 Li-Ion Cells.
Test 1 Setup
Test 1 Setup Diagram
Test Result


Test 1 Results: Successfully displayed the 20V input for each
device on the EVM Software GUI with the PC.
Test 2 Results: Successfully recognized all 6 devices in the
EVM stack while all devices were hooked up to the Li-Ion Cells.
Test 2 Setup
Test 1 Results:
V BRICK
shows the
20V DC input
Test 2 Results: Displaying expected results
Implementation/Testing
MSP430
 Test 1:The fault line was tested to ensure proper
input to the MSP430
 Test 2: A constant voltage was applied to the ADC to
ensure proper charging during the constant voltage
phase (Program was set to regulate at 35 VDC)
 Test 3: A voltage proportional to the current was
applied to the ADC to ensure proper charging during
the constant current phase (Program was set to
regulate at 1.5 A)
Test 2 & 3 Setup
Test Result
 Test 1 result: proper input voltage was detected at
the fault line
 Test 2 result: the proper PWM output was detected
and the 35 VDC was kept constant.
 Test 3 results: the proper PWM output was
detected and a 1.5 A output was kept constant.
Test 2 PWM Waveform
Conclusion / Lesson Learned




With global demand for oil increasing and supplies more difficult to obtain,
the price of oil based fuels for transportation is expected to rise. The need to
find a viable alternative to oil necessitates researching in electric
alternatives. Electric vehicles have to be convenient, safe, and affordable to
meet the needs of consumers without major sacrifices in perceived quality of
life. Lithium ion batteries support a high energy density and are the
preferred source of mobile electric power. This project implements a solution
for a battery management system for a large number of lithium ion cells.
Integration of several smaller complex systems to create a successful overall
design is a time consuming process
Theoretical models don’t always work as expected so flexibility is necessary
The technical aspects of the charging cycles of lithium ion batteries
Future Work


Our prototype system charges 18 series cells using two EVMs
The next step is to develop a large scale system that charges 90 cells and
16 parallel packs
Project Success

The individual components have been
successfully built and tested
 Boost Converter
 EVM boards
 The programming of MSP430 to control the
charging cycle

Final Testing
 All discrete components integrated
 Partial battery charge with cell balancing
successful
Questions ?