2012 Toyota RAV4 EV Prototype

2012 Toyota RAV4 EV Prototype


When the RAV4 EV reaches its Phase One stage next year, and a limited-production vehicle goes on sale, it will have one key difference versus the Phase Zero prototype we drove in the San Diego area this past week. While the RAV4 EV prototypes have a proprietary charge connector from Tesla Motors, the production version next year will have an industry standard, 220-volt SAE J1772 charge connector.

But there definitely won't be any quick-charging capability.

A quick charger would provide a lot of additional cost and mass, Toyota decided. According to Brown, adding a quick charger to the EV—including its additional data-porting capability, additional cooling hardware, and other safeguards—would bring up to 40 kilograms (88 pounds) of additional weight.

Using the RAV4 EV's current charging technology, the 37 kWh batteries take 12 hours to reach a full charge with 240V, or about 28 hours with a standard household outlet.

Smart and fast

Level 3 quick charging—sometimes also called rapid charging or DC fast charging—allows more than 500 volts DC and up to 125 Amps, for much faster charging than the lower-Amp, household-based AC charge connectors. The key to effective and safe DC fast charging is the CHAdeMO connector, which allows the charger to receive data from the car regarding how much voltage to send at a given time.

In the Nissan Leaf, it would allow you to add extra range some days in about the time it would take to grab lunch, or walk out for a cup of coffee. In the Leaf, charging from 20 percent to 80 percent can take less than 30 minutes.

Why is that connector so important? Because a lithium-ion battery charges more slowly as it reaches capacity; excess current can result in heat buildup, which can prematurely destroy batteries—or worse, start a fire. For this, CHAdeMO connectors include additional cooling systems and sensors; it's all connected, and with safeguards on both the vehicle and charger side.

Fast Charging 2011 Nissan Leaf

Fast Charging 2011 Nissan Leaf

Quick-charging is offered as an option on the 2011 Nissan Leaf, but those familiar with EVs and charging have pointed out that, given the price of the hardware and development, that's well under cost. Then again, it spurs development of the infrastructure—and it's the same philosophy Toyota followed with its Prius hybrid many years ago. The automaker just announced earlier this week that it has sold more than a million Prius vehicles in the U.S., and it passed the three-million mark worldwide earlier this year.

Not a viable option?

"We don't see it as being a viable option to our customers right now," said chief engineer Sheldon Brown, who said that Toyota is going to wait to see what the SAE decides on Level 3 charging first.

General Motors has also opted not to install the CHAdeMO connector in its 2011 Chevrolet Volt. In addition to the Leaf, the Mitsubishi MiEV is the only other EV capable of rapid-charging.

Brown does say that the project allowed for "some flexibility in the design long-term to be able to accommodate that" at a later date, when it could be introduced as a lifecycle enhancement once they're assured that the CHADEMO connector is the rapid-charging standard.

Of course by then there might be tens of thousands of compatible Leafs on U.S. streets, already ready for a quick charge.