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

Prius PHEV

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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

See Prius PHEV Battery Options & Battery Pack Configurations

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

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