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EAA-PHEV

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This is an Initial Page for the EAA-PHEV Projects.
Which will focus on the Prius Plus Conversions for the moment.
CalCars has a great PHEV talking points to bring you up to speed regarding Plug-in Hybrids.

Maillist

See the Maillist for past messages and instructions for joining the list.
An archive of the maillist can also be found here http://groups.yahoo.com/group/eaa-phev.
Those who join the group are reminded to observe standard email etiquette and be respectful of each other. The information is provided as a public service and the EAA assumes no liability for its use. Anyone modifying a Prius or other vehicle does so at their own risk and may void their manufacturer's warranty.

In addition to the maillist you can Post any comments, questions, or suggestions you may have to the discussion page, or view the Talk:EAA-PHEV page with the discussion link in the menu at the top of the page.

You do not need to register on this wiki site to join the maillist. However if you intend to contribute to these pages you should create an account and login. Although even this is not strictly required as anyone can edit pages at the moment, it does help keep track of who's changing what, and you get a page of your own!

Disclaimer

  • Use this information at your own risk, there is no warranty expressed nor implied. Even should you perform these modifications to the letter you could still cause damage to any number of components in your Prius and cause it to no longer function. In performing some of these modifications you may also void your warrenty with Toyota.
  • HV warning: The Prius Traction Battery is a HV (High Voltage) Battery and could cause serious injury or death if proper precautions are not taken while working with it.

See also: http://www.airlabcorp.com/Prius/priusdisman.pdf - for dismantle and safety warnings

Terms

  • MFD is the Multi-Function Display, or the Touch Screen which is standard on all Prii.
  • CAN is the Controller Area Network used within the Prius which all the computer systems use to communicate.

EV-Mode

Ron Gremban [RDG]: 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 modal 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. Once 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. [end RDG]

SOC Spoofing

[RDG] 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. [end RDG]

SOC management

[RDG] 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. [end RDG]

Schematics

  • priusplushv1.pdf First Draft of HV System Wiring by Nick Viera.
  • [RDG] Because of the points mentioned under SOC Spoofing above, CalCars' overall PRIUS+ circuit diagram is still in flux, and definitive answers about it are as yet unavailable. I'll provide more info ASAP, but have an intense schedule at least through early December [end RDG]

Batteries

  • Stock Prius Battery Specs.
  • 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 probably be disconnected while in PHEV mode.
  • CalCars has used 18 B&B 20Ah 12v SLA PbA batteries from www.electricrider.com
  • EDrive plans on using more exotic 40Ah Li batteries from Valence.
  • You may want to use some Anderson high power connectors for DC.

Minimum Requirements

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

  • The 6.5Ah Stock NiMH pack consists of 168 cells (28 modules) in series. 1-3 miles. [RDG] 60% nominal to 45% minimum SOC for EV-only => 15% or 6.5 Ah or 1Ah, providing 1 mile EV-only range. [end RDG]
    • Nominal Voltage is 201.6v and fluctuates from 180-270V during use.
  • The 20Ah (12Ah at 2C rate) CalCars PbA pack consists of 18 12v BB Battery EVP20-12B modules from ElectricRider.com in series. ~10 miles EV-only or 20 miles mixed-driving PHEV range. Nominal Voltage is 216V.
  • The 45Ah EDrive Li-ion pack consists of 18 12V U-1 U-charge modules in series. ~30 miles EV-only or 60 miles mixed-driving PHEV range.
    • Nominal Voltage is 2??v, ranging form ???v to ???v.

[RDG] 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 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 driving PHEV range.

California Cars Initiative PRIUS+ Project Preliminary Public Chemistry-neutral Battery Pack Specification Subject to Change 6/17/05 Ron Gremban

Definition: SOC == state of charge

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

[end RDG]

Chargers

File:Prius Charger.jpg
THS Charger
  • CalCars uses a Busha(sp) (link)(model)
  • PFC-20 Running off Prius HV Pack [1] Charging a BEV. This charger could run in both directions.
    • charging from the grid to the additional pack
    • charging from the additional pack to other EV's
    • charging from the Prius ICE/Gas to other EV's (up to 10kW)

CAN-View Scanner

File:Inimech.jpg
One of the graph screens
CAN-View local gallery
See the Official Website

This is a MFD Integrated CAN Scanner, named CAN-View.
The Official Website is http://www.hybridinterfaces.ca

Additional accessories

These additional features are supported by the 2nd version of the CAN-View, some require additional hardware.

Other CAN scanners

Links

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