Toyota RAV4 EV key for meeting California ZEV requirements; Tesla powertrain uses Model S components
3 August 2012
|The RAV4 EV. Click to enlarge.|
Toyota held its first media briefing and drive for the RAV4 EV (earlier post), due to go on sale later this year in California. The converted RAV4 is the result of the partnership between Toyota and Tesla Motors announced in May 2010; Toyota has contracted for 2,600 units.
In remarks during the briefing, Bill Fay, Group Vice President & General Manager, Toyota Division, noted that the RAV4 EV is an important element of Toyota’s plan to meet the Phase 3 requirements of California’s ZEV mandate (earlier post) for the 2012-2014 timeframe. Fay says that the company is planning to sell the full complement of 2,600 RAV EVs in California, plus 30,000 Prius plug-in hybrids and to introduce iQ EV urban car sharing programs to achieve ZEV compliance.
Accordingly, the RAV4 EV is only being sold in California. Depending upon consumer response and demand, Toyota could consider contracting with Tesla for additional units, perhaps to be rolled out in cities such as Boston and New York, or in other California ZEV states.
Some people have called the RAV4 EV nothing more than a compliance car. Let’s get one thing straight. The ZEV mandate been around for more than 20 years. It’s a fact of life. Will the RAV4 EV help us meet our compliance requirements? Absolutely. Did we create a barebones EV just to earn credits for the mandate? Absolutely not.—Bill Fay
The RAV4 EV is priced at $49,800, which can drop to below $40,000 with federal and state incentives. Based on its research, Toyota has a clear customer in mind, Fay said. The target buyer is married, 45–60 years old, highly educated, and is an affluent and evangelistic early adopter. He or she owns a home, which is perhaps solar-powered. The target buyers have strong personal convictions on the environment, oil use, and cutting edge technology. “The pool of buyers,” noted Fay, “is small.”In its sales pitch, Toyota plans to emphasize product attributes such as driving range, dynamic performance and telematics. The RAV4 EV will be offered with only one spec, no options, and a simple color palette.
We’re going to find out what the market for EVs is. Our approach is to bring a great product to a select market that’s very open to this kind of technology. We do very well in California. and I think this will give us a good idea of overall consumer acceptance of EVs.—Bill Fay
Basics. Twenty-two months after the project announcement, Toyota and Tesla engineers revealed the RAV4 EV at Electric Vehicle Symposium 26 in May 2012. To manage such a compressed timetable, Toyota engineers devised the eFAST process (early field and suitability testing), a new protocol specifically put in place for the RAV4 EV to validate and confirm vehicle performance.
The RAV4 EV combines a Tesla-designed and produced battery and electric powertrain with Toyota’s most popular SUV model. The current RAV4 EV uses Tesla Model S powertrain components; earlier Phase 0 builds used components from the Roadster.
The Tesla-supplied motor is an AC induction motor, which is a departure from Toyota’s practice of using synchronous permanent-magnet motors in their hybrid vehicles. A fixed-gear open-differential transaxle has a gear ratio of 9.73. The RAV 4 offers two drive modes: Normal and Sport.
Peak power output of the motor is 154 hp (115 kW), with peak torque in normal mode of 218 lb-ft (296 N·m), and peak torque in sport mode of 273 lb-ft (370 N·m). Maximum vehicle speed in Normal mode is 85 mph (137 km/h); maximum in Sport mode, which also has a more aggressive accelerator pedal feel, is 100 mph (161 km/h).
The battery pack is a 386V Li-ion pack comprising about 4,500 cells and rated at 41.8 kWh of useable energy at full charge. Power output is 129 kW max. The RAV4 EV features a 10 kW onboard charger (SAE J1772 240V, 40A input).
The RAV4 EV has two charge modes: Standard and Extended. In standard mode, the high voltage battery charges only up to 35 kWh and the vehicle is expected to achieve an EPA-estimated driving range rating of 92 miles. Extended Mode allows the battery to charge to its full usable capacity of 41.8 kWh, providing an anticipated EPA-estimated driving range of 113 miles. Standard mode is designed to optimize battery life over range; however, the 8-year, 100,000-mile battery warranty cover the packs regardless of the mix of charge modes over the packs’s life.
|Standard Mode||Extended Mode|
|40A/240V||5 hrs||6 hrs|
|30A/240V||6.5 hrs||8 hrs|
|16A/240V||12 hrs||15 hrs|
|12A/120V||44 hrs||52 hrs|
Toyota has partnered with Leviton for a 40A, 9.6 kW Level 2 residential charger.
Charge modes and range. The determination of EPA-rated range for the RAV4 EV is a bit convoluted, noted Sheldon Brown, Executive Program Manager for the RAV4 EV at the Toyota Technical Center in Michigan. Basically, EPA calculates EV range based on the J1634 test procedure, reduces it by 30% and harmonically averages the results them for city and highway usage. However, the RAV4 EV has two defined charge modes.
In our recent discussions with EPA, the certification side decided that they should apply the user-selectable interpretation of the drive mode policy—a policy we felt was meant to govern modes that impacted efficiency. And now they are applying that to how we calculate range.
Since we have the two different modes, we have to test both the city and highway in both the normal and extended mode. We average those, take the 30% reduction, and then once again harmonically average the city and highway cycles. So, in a standard mode of 92 miles, in an extended miles we might see a label range of 113 miles.—Sheldon Brown
What will appear on the label is likely, however, to be around 103 miles, with a label fuel efficiency of 76 mpge.
My point is not that the EPA is incorrect. It's a matter of interpretation. We feel that their interpretation is misguided in this particular application. But it really is confusing to the customer and to the general public when we talk about range calculation. Averaging two different modes and coming up with a number is very difficult to completely understand.—Sheldon Brown
In developing the RAV4 EV, the engineering team shot for a range of about 170 miles on the LA-4 cycle—which simulates an urban cycle with frequent stops. Real-world data gathered during the testing of six Phase 0 prototypes found a distribution of ranges that reached 145 miles, with a concentration being in the 80–100 mile bins (partly due to the routes designed for the eFAST methodology, Brown noted).
The 80-105 mile or so range corresponds to about 28-34 kWh of energy use. This suggests, Brown said, that the RAV4 EV Normal mode capacity has a real-world range of approximately 100 miles.
The obvious question is that if you’re going to take a penalty on the EPA label, why offer two modes of range? Frankly speaking, we think it’s the right thing to do. Another issue that is always relevant is battery degradation over time. It is inherent in the technology but it is influenced by a great many factors. Among those factors is depth of discharge.
Over 96 % of the population travels to and from work less than 60 miles. We recognize that getting to and from work is not the only requirement that you have. So we added an additional 20 miles as a buffer. With our standard mode charge, basically with that 20 mile buffer, we still can see that 96% of the populations is covered.
What we are saying is that our customers, once they start to understand the technology, aren’t going to need [the extra charge capacity] on a daily basis. Its great to have when you do need it. As we talk about larger format batteries, it is important to talk about judicious battery use.—Sheldon Brown
|E-FAST range data (top) and energy use (bottom). Click to enlarge.||E-FAST and customer data. Click to enlarge.|
EV range optimization. Toyota engineers devised a number of strategies to help optimize the available EV range on the Toyota RAV4 EV. The climate control system has three modes which allow the driver to select his or her preferred level of comfort and EV driving range. In NORMAL mode, the climate control system operates in the same manner as a conventional vehicle and provides the maximum comfort level, but also draws the most power, which in turn reduces the EV range.
ECO LO mode is recommended to achieve a balance of cabin comfort and improved range through reduced power consumption of the blower, compressor and/or electric heater. In cold weather, ECO LO also automatically activates and controls the seat heaters to optimal levels based on the cabin thermal conditions.
ECO HI further reduces blower, compressor and heater levels and also automatically activates the seat heaters if necessary. The use of ECO LO can reduce the climate control system power consumption up to 18% compared with NORMAL while ECO HI offers up to 40% power reduction compared to NORMAL. Thus use of either ECO LO or ECO HI mode extends the vehicle’s EV driving range.
Remote Climate Control allows drivers to pre-cool or pre-heat the vehicle prior to driving while the vehicle is plugged-in, which conserves battery charge and EV range. The Remote Climate Control system can be set by a timer on the navigation display. It can also be activated using a smart phone.
The Toyota/Tesla designed cooperative regenerative braking system works to minimize the vehicle’s kinetic energy loss during stopping. The system recovers the energy and converts it to electrical energy, which recharges the battery and extends driving range. The vehicle slows down while energy is captured. The addition of cooperative regenerative braking increases driving range by up to 20%.
The Toyota RAV4 EV also offers a low coefficient of drag and low center of gravity. At 0.30 Cd, RAV4 EV achieves the lowest coefficient of drag of any SUV in the world. Compared with the gasoline-powered RAV4, at 0.35 Cd, Toyota re-styled the front bumper, upper and lower grill, side mirrors, rear spoiler, and under body design to optimize air flow around the vehicle. The RAV4 EV’s battery pack is mounted low and to the center of the vehicle, contributing to a more sedan-like ride.
Powertrain Control. The RAV4 EV’s gauge system includes a “turtle light”, or reduced power indicator, which Toyota last used on its 2001-2003 first-generation (North America) Prius. The turtle light illuminates when HV battery pack state of charge (SOC) or temperature is low, or when a powertrain component overheats.
Powertrain Cooling Systems. The powertrain uses two independent coolant loops: one for the electric motor and charger assembly, and another for the battery and DC-DC converter. The battery coolant loop uses a chiller, which passes refrigerant through a circuit adjacent to the battery cooling circuit, for extra cooling capacity when needed. Both coolant loops use electric coolant pumps and front-mounted radiators.
The vehicle’s DC-DC converter also powers a high-voltage heating system, to heat the battery pack coolant during operation in low ambient temperatures. Both coolant loops use Zerex G48 or Glysantin G48 coolant.
The vehicle’s thermal control ECU regulates battery temperature. A “pre-climate” function, which is scheduled through the vehicle’s navigation screen or via a smartphone app, can be used to schedule a departure time. Assuming that battery pack SOC is sufficient, the pre-climate system can be used to set vehicle interior temperature as well as optimum battery temperature at time of departure, even if the vehicle is not plugged in and charging.
Driving range is prioritized over cabin comfort during low SOC events, and air conditioning system operation is suspended when the RAV4EV’s battery pack SOC drops below 3%, and resumes when SOC rises about 6.5%.
On-Board Self-Diagnostics. Although battery-electric vehicles are not required to have conventional OBD-II on-board diagnostic systems for their, many OEMs have elected to carry over the OBD-II diagnostic link as well as OBD-II diagnostic trouble code (DTC) definitions and nomenclature to their EVs. However, the RAV4EV powertrain uses two onboard self-diagnostic systems:
OBD-II system: Some powertrain DTCs and scan data can be accessed with Toyota’s Techstream scan tool. However, most of this data, such as airbag or shift selector codes, is somewhat peripheral to the RAV4EV’s powertrain components.
Proprietary system: Most powertrain component codes and data (i.e. related to the RAV4EV’s battery pack, charge control system, inverter, electric motor, and DC-DC converter) use a proprietary formant and communication protocol, and are accessed by connecting a device called an “electric propulsion diagnostic tool” to a unique connector at the rear of the vehicle.
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