General Disclaimer:   (HV) (DC) injury or death hazard,   use at your own risk,   may void warranty.

Difference between revisions of "Prius PHEV"

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(→‎Schematics and Documentation: added small schematic map.)
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==EV-Mode==
 
==EV-Mode==
 
=== Enabling EV-Mode Button ===
 
=== Enabling EV-Mode Button ===
* Enabling the [[SEVA:User:Rjf/Prius_Modifications#Enabling_EV-mode_Button_.22H14_.2327_to_ground.22|EV-Mode Button]]
+
See [[Prius EV Mode]]
EV-only mode is auto canceled outside of the following limits:
 
* >=180V
 
* >=45% SOC (mode cannot be entered unles SOC is >=50%)
 
* Accelerator pedal position <=120 (out of 255), corresponds to approx. 120A or 24kW
 
* Vehicle speed <34 mph (55 kph)
 
* Defrost not selected (and possibly some other control selections)
 
Notes:
 
* The ICE will start 7 seconds after vehicle startup unless EV-only mode is entered during that time.
 
* Once the ICE starts the first time during a trip, it will not stop until it has warmed up.
 
* The A/C compressor is electric, and the A/C will work while in EV-only mode.
 
* When the EV-only mode is entered, the hybrid model screen will show.  A beep will be heard only if that screen wasn't already showing.
 
* Three beeps are heard whenever EV-only mode is requested but not allowed, and when it is auto canceled.<br>One must wait around five seconds before a new EV-only request is acknowledged.
 
Regenerative braking is limited by all of the following:
 
* 120A
 
* ~30A if SOC is >=80%
 
* HV 250-270V (progressively greater limitation)
 
None of the above voltage limits have been tested for temperature-based variations.
 
  
 
===SOC Spoofing===
 
===SOC Spoofing===

Revision as of 10:52, 10 March 2006

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This is an Initial Page for the EAA-PHEV Projects page, which will now be dispersed about the new website... There are other PHEV projects on the History and PriusPlus pages. CalCars has a great PHEV talking points to bring you up to speed regarding Plug-in Hybrids.

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Disclaimer

General Disclaimer:   (HV) (DC) injury or death hazard,   use at your own risk,   may void warranty.

HV (High Voltage) DC (Direct Current) Warning: Traction Battery Packs, Motors, Chargers, and other HV sources could cause serious injury or death if proper precautions are not taken while working on or around such High Voltage Direct Current sources.

Use this information at your own risk: There is no warranty expressed nor implied and we are not liable for any of your past, present, nor future actions. Even should you perform these modifications to the letter you could still damage any number of components in your vehicle causing it to no longer function. Even if it appears to function properly your actions may cause it to self destruct with collateral damage to surrounding properties other than your vehicle. By utilizing these ideas and instructions in an attempting to enhance national security, reduce gas consumption, vehicle "emissions", your carbon footprint, or smog, you do so at your own risk & peril.

Warranty: In performing some of these modifications you may void your warranty with the vehicles manufacturer.

See also our My wiki:General disclaimer

Terms

  • EAA = Electric Auto Association.
  • PHEV = Plug-in Hybrid Electric Vehicle.
  • SIG = Special Interest Group.
  • BMS = Battery Management System.
  • SOC = State Of Charge, is a percentage of the charge remaining. 20% SOC is 20% full.
    • DOD = Depth Of Discharge, the opposite of SOC, 20% DOD is 20% empty or 80% full.
  • CAN = Controller Area Network, used for vehicle communication between computer systems.
  • MFD = Multi-Function Display, or the Touch Screen which is standard on all Prius
  • IMA = Integrated Motor Assist, Honda Insight, Honda Civic Hybrid, Honda Accord Hybrid.
  • HSD = Hybrid Synergy Drive, Toyota Prius, Toyota Highlander, Lexus RX 400h.
  • AHS2 = Advanced Hybrid System 2, General Motors and DaimlerChrysler
  • FHS = Full or Ford Hybrid System, Ford Escape Hybrid, Mercury Mariner Hybrid.
  • V2G = Vehicle-to-grid, bi-directional charging and grid load balancing.
  • AER = All-Electric Range, the distance a vehicle can travel on its battery alone.
  • MPGe = Miles Per Gallon of Gasoline equivalent.

EV-Mode

Enabling EV-Mode Button

See Prius EV Mode

SOC Spoofing

Note: More information is now available in PriusPlus (.doc) and the EAA-PHEV_Maillist:.

The Prius' battery management computer (BMS, called the Battery ECU) communicates to the main hybrid computers via the CAN bus. It indicates battery voltage, current, temperature, and its estimates of state-of-charge (SOC), and maximum allowable charge and discharge current.

The BMS' estimate of SOC is critical, as the hybrid controller keeps SOC within 40-80% (the lower and upper limits of the (nonlinear) display graph), and tries to keep it around 60%. When the SOC is above 60%, the hybrid controller works to discharge the battery by using battery power (and less gasoline) even during normal cruise. This increases to around 30A (~6kW) at 70% and above.

When the SOC is below 60%, the hybrid controller works to charge the battery by making the ICE work extra hard even during normal cruise. Below 40% SOC, stranger things happen and it is difficult to get the engine to put out much power at all.

For a PHEV, the object of SOC spoofing is to keep the BMS's indicated SOC at 80% or above until the battery is discharged enough to accept significant regenerative braking current; then between 70-80% -- to force less gasoline use even during non-EV-only mode -- until the battery's real state-of-charge has come near its lower limit. At that point, the BMS's indicated SOC should hover around 60% to keep the battery's real state-of-charge from trending further downward (bad for the battery) or upward (thereby wasting gasoline).

Dan Kroushl did some experiments with higher voltage batteries that proved that the BMS's indicated SOC can be spoofed (Thanks, Dan!). That led me to do enough further experimentation to discover that it is definitely possible to do what I indicated in the above paragraph, and generally how to do it. However, the circuitry and programming to do so is still in development. It generally involves, as needed, providing a higher voltage to the BMS than the actual battery voltage.

Toyota's BMS also checks the voltage of 13 taps on the OEM battery. These voltages must be equal to each other or the BMS will indicate a fault. Since few PHEV battery packs, unlike the OEM pack, are divisible into 14 equal subpacks, these tap voltages must be spoofed, too. Fortunately, it has been found that a fairly simple voltage divider can accomplish this.

Because of all of the above, CalCars' overall PRIUS+ circuit diagram is still in flux, and definitive answers about it are as yet unavailable.

SOC management

Note: More information is now available in PriusPlus (.doc) and the EAA-PHEV_Maillist:.

Here is the minimum needed in terms of a computer for spoofing the Prius' built-in BMS:

  • CAN message reading and parsing (CAN bus writing is NOT necessary or even desirable)
  • The ability to separately close and open two reed switch contacts based on CAN information
    • one to set EV-only mode, based on it not already being set, speed <34 mph, power request <120 (out of 200), SOC >49%, and a few other parameters.
    • one to set a voltage boost (to be explained later) to keep perceived SOC within a given range until the battery is sufficiently depleted
  • Amp-hour integration and display from the appropriate CAN bus messages
  • HV battery voltage and current display (both analog and digital desirable) from the appropriate CAN bus messages
  • Display of trip info (since reset): # of CAN errors (important for debugging), odometer, milligallons of gasoline used, Amp-hr and/or kWh used, trip milligallon/mi, Wh/mi, and mpg, highest peak charge and discharge currents, highest and lowest HV battery voltages, and the battery's internal resistance (beginning, current, and end)

Additional displays, desirable but not necessary:

  • Not strictly necessary, but SUPER desirable: storage of CAN trip running data on a removable medium (like a CompactFlash card) for later analysis.
  • Small graphical engine tachometer (but see rectangular suggestion below)
  • Gasoline use rate (milligallon/min and/or milligallon/mi (inverse of mpg), or just a binary for gasoline being used
  • Tiny graphical brake cylinder pressure (sum of that for each wheel), to indicate amount of non-regenerative braking being used

A very cool display would be two rectangular graphs indicating engine and electric power:

  • Engine power (e.g. blue for combustion): vertical: RPM, horizontal: torque
  • Electric (e.g. red for discharge, green for charge): vertical: HV battery voltage; horizontal: HV battery current (absolute value)

The areas can be calibrated so that they show the relative power being produced by the electric motor vs. the engine. The same pair of rectangles could display and compare the power going into regenerative braking vs. that being wasted in the friction brakes.

Batteries

Any battery which meets the minimum requirements could be used to replace the Stock Prius NiMH battery pack. The stock battery does not necessarily need to be removed, but should be disconnected while in PHEV mode due to serious problems that can occur from paralleling this sort of battery. Adding more than 300 lb to the vehicle's weight is not recommended, at least without beefing up the suspension; removing the OEM battery pack removes around 80 lb.

This application is on the edge of the capabilities of lead-acid (PbA) batteries. CalCars' PbA conversion works, but just barely. The battery pack's internal resistance, though O.K. at high states-of-charge (SOC) is twice as high at low SOC. As this is what ultimately limits discharge, it also means that ordinary hybrid operation is compromised, too, once this low SOC is reached. Additionally, and possibly most important, low temperature operation is very compromised. Range is reduced at least 20% at 50 vs. 70+ degrees F, and at freezing temperatures CalCars' PRIUS+ wouldn't drive at all on the PbA pack!

  • CalCars has used 18 EVP20-12B B&B 20Ah 12v SLA PbA batteries from ElectricRider.com (~270 lb and 12Ah at 2C rate) for a total of 3.1 kWh. These PbA batteries have exceptional high power capabilities, cost $750 total, and deliver 10 miles of pure EV driving or 20 miles of doubled gasoline mileage in mixed driving per charge. CalCars' first set lasted 200 cycles or $0.35/mile -- but see RonG's further information under Charging below.
  • Another PbA possibility is the Odssey PC625 by EnerSys Inc. They are slightly lighter for the same high rate capacity and may have longer cycle life than the EVP20-12B. I believe these are what used to be the much-touted Hawker brand. More info on these batteries, where to get them, and for how much will be forthcoming -- and, again, see RonG's further information under Charging below.
  • CalCars has nearly completed a project with Electro Energy Inc. using a custom pack of their specialized NiMH batteries. Though more expensive, it will weigh the same as the EVP20-12's but provide more than double the range, better performance, probable low temperature operation, and much longer expected lifetime. We are hoping that Electro Energy will make these available for conversions later this year (2006). Stay tuned.
  • EDrive plans on using 18 exotic 12V U-1 U-charge 40Ah @C/5 Li-ion batteries from Valence for a total of 9.9 kWh.
  • Useful files by Ron Gremban:
  • You may want to use some Anderson high power connectors for the DC connections.

Minimum Requirements

We will focus on the Voltage requirements, as the AmpHour capacity of the pack may vary depending on who's implementing it and for what type of useage for various ranges from 5 to 50 or more miles. While a PbA pack may only deliver about 1/2 its nameplate capacity (due to Peukert's Law, which does not affect other chemistries) a Lithium pack may be able to deliver all of it's nameplate capacity. It all depends on how the battery's capacity is rated. The Prius consumes about 1 Ah or 300 Wh per mile.

  • The 6.5Ah Stock NiMH pack consists of 168 cells (28 modules) in series.
    • 60% nominal to 45% minimum SOC => 15% of 6.5 Ah is 1 Ah for 1 mile EV-only range.
    • 80% maximum to 45% minimum SOC => 35% of 6.5 Ah is 2.2 Ah for > 2 miles EV-only range.
    • Nominal Voltage is 201.6V, ranging from 180V to 270V durring use.
  • The 20Ah CalCars PbA pack (12Ah at 2C rate)
    • Delivers ~10 miles EV-only or 20 miles Mixed-mode driving PHEV range.
    • Nominal Voltage is 216V, still ranging form 180V to 270V durring use (range set by Toyota's hybrid system).
  • The 40Ah EDrive Li-ion pack
    • Delivers ~30 miles EV-only or 60 miles Mixed-mode driving PHEV range.
    • Nominal Voltage is 230V.

CalCars' published chemistry-neutral PRIUS+ battery spec is reproduced below. We have found 18 12V PbA modules or 180 NiMH cells in series to be near optimum.

Note: our PRIUS+ gets approx. 1 mile of pure EV range (or 2 miles of Mixed-mode driving range, with double normal gasoline mileage) per Amp-hr expended from the battery. Therefore, a 30Ah battery, used to 70% depth-of-discharge (DOD) would provide 24 miles of EV-only range or 48 miles of Mixed-mode driving PHEV range.

  • California Cars Initiative PRIUS+ Project - Preliminary Public Chemistry-neutral Battery Pack Specification
  • Subject to Change 6/17/05 By Ron Gremban
    • Voltages:
      • Maximum (during regenerative braking, 120A or max for SOC): 260V
      • Minimum (during 120A discharge at minimum normal SOC): 180V
      • Nominal: 210-230V (depends on the chemistry)
    • Amp-hr at 60A rate: 30-50 (5.5-10.0 kWh)
    • Max intermittent discharge rate: 200A
    • Max intermittent charge rate (when SOC is low enough to accept this full rate): 120A
    • DC internal resistance*, over normal range of SOC: Less than 0.25 ohm (0.20 ohm desired)
    • Charge equalization: Please indicate requirements and provisions for charge equalization
    • Thermal management: Please indicate requirements and provisions for thermal management
    • Min cycle life*: At least 1000 cycles between normal SOC limits; 2000 cycles or more highly desired
    • Max battery pack weight*: 300 lb (136 kg); 170 lb (77 kg) desired (replaces 70 lb hybrid battery)
    • Max price*: $800/kWh or less to CalCars, including charge balancing, cooling, thermal management, and SOC monitoring
    • Projected high-volume auto manufacturer's cost in two years*: $0.40 or less per kilowatt-hr lifetime throughput
  • *The values of these parameters should be maximized (or minimized, as appropriate), given a reasonable cost of doing so

Battery analysis by Richard

per EAA-PHEV_Maillist:2005./12./2:
I have completed my analysis for the battery pack and am attaching it. The first attachment explains the analysis and the second is a spread sheet of some of the data I ran.

Chargers/Charging

See Battery Chargers

User Interfaces

See Prius PHEV Schematics

Schematics and Documentation

See Prius PHEV Schematics

EAA-PHEV-PRIUS-Combined.png

Navigation Image

Management Pseudo Code

See Prius PHEV Pseudo Code

Installation Photos

See Prius PHEV Photos