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Add an additional battery and charger to compliment the Prius C’s existing hybrid drive system to improve overall efficiency.

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Presentation on theme: "Add an additional battery and charger to compliment the Prius C’s existing hybrid drive system to improve overall efficiency."— Presentation transcript:


2 Add an additional battery and charger to compliment the Prius C’s existing hybrid drive system to improve overall efficiency

3  Will roughly follow what is known as the “contactor method” already proven in full-sized Prius conversions  LiFePO4 pack as extra battery with higher voltage than hybrid battery to avoid using a DC-DC converter  Connected to Hybrid Drive system in parallel with original hybrid battery  Battery connection controlled by an electrically controlled contactor  Contactor controlled by an Arduino microcontroller  Arduino monitors state of charge, current, voltage and cell under/over voltage and sets state of the contactor

4  Get Arduino to read the CANbus, specifically the State of Charge (SOC) of the Prius’ battery  Build the hybrid battery pack, including Battery Monitoring System  Build the interface board between Arduino and the battery as well as instrumentation and control to include  LiFePO4 battery current  Relay for charge control  Main contactor control  Display system for hybrid pack information  Display hybrid pack SOC  Warning for system faults  Incorporate LiFePO4 pack battery charger  Develop Arduino code for system control

5  CANBus Shield gives Arduino the ability to read and log CANBus data  Reading of CANBus is necessary to find the Hybrid Battery’s SOC to know when to open and close the contactor between it and the LiFePO4 battery to prevent over/under charging

6  I have already developed and Arduino sketch (program) to read and log CANBus data

7  No publicly available data identifies PID codes for Prius C’s unique attributes  Reverse engineering was necessary to find the Hybrid Battery’s SOC on the CANBus

8  LiFePO4 chemistry chosen due to proven use in full-EV conversions  Long cycle life  Flat discharge curve  High power/weight  Hybrid battery is 144V nominal  LiFePO4 nominal voltage will be 154V to allow for low-rate charge of Hybrid battery when connected in parallel  48 Cell, 20AH GBS Batteries, 3KWH pack

9  To provide LiFePO4 cell under/overvoltage (UCV/OCV) protection and alarm as well as inter-cell balancing, a Battery Management System(BMS) is necessary  Ready made systems for full-EV conversions are expensive (~$1000 for my application) and redundant to capabilities inherent to Arduino

10  Maxim MAX11068 IC chosen for my application  Provides UCV/OCV alarms  Total pack voltage  Inter-cell balancing  Pack temperature  Two wire interface (I2C) to Arduino to provide alerts  MAX11068 Evaluation Kit (~$250) will be used to reduce time and cost in producing PCB

11  A small PCB will be necessary to support several interface features  Provide 12V Battery power to Arduino and interface systems  Transistor interface to activate contactor  Allegro MicroSystems ACS758 IC chosen to measure bidirectional current for LiFePO4 pack  Relay for controlling LiFePO4 battery charger  Relay for sensing if AC is still plugged in

12  A small LCD will be mounted in view of the driver to provide information about the system  LiFePO4 pack voltage, current, SOC  State of contactor  Warning for system faults

13  Elcon PFC 1500 chosen  Mounted onboard to allow for charging away from home  Will recharge a fully discharged pack within three hours via 120VAC

14  Numerous software and hardware features  Software trip of contactor ▪ OCV/UCV ▪ Abnormally high charge/discharge current ▪ Over-temperature  Hardware ▪ Fuses for main cabling ▪ Barrel switch near driver to allow for manual disconnection of LiFePO4 pack ▪ Inertial switch to trip contactor in event of a crash

15  Initialization  Determine SOC of Hybrid battery  Verify system health  If Hybrid SOC 20% SOC, no OCV/UCV or over-temp)  Shut main contactor  If Hybrid SOC >90% or any fault detected  Open main contactor  SOC for shutting and opening contactor will be modified after initial testing to optimize use of stored energy in LiFePO4 pack

16  Stock Prius C advertises ½ mile on EV only mode  0.9KWH NIMH pack, max DOD 45%  With addition of 3KWH LiFePO4 pack, max 80% DOD, up to 6 additional miles in EV only mode  In blended mode, full sized Prius conversions have resulted in >80MPG during normal commuting  Due to smaller vehicle size and larger proportional pack size, expect as good or better than 80MPG

17 Follow my progress at:

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