Exclusive Video: Interview with RAV4 EV Engineer

By · November 22, 2010

Toyota RAV4 EV test mule

Toyota RAV4 EV mule in testing

Battery pack of Toyota RAV4 EV test mule

Photo showing battery pack under the Toyota RAV4 EV test mule

As we reported, Toyota unveiled the RAV4 EV prototype last week at the Los Angeles Auto Show. Minutes after the presentation, I spoke with Greg Bernas, the Toyota engineer in charge of the project. It’s still early days in the development of the vehicle, which is due out in 2012, but Greg was able to share a few choice details about the current status of the project.

  • Toyota RAV4 is currently in Phase 0, in which Tesla components were applied to the RAV4, for testing and modifications to evaluate range.
  • Current testing has the battery pack sized between 30 kWh and 40 kWh, to get a desired 100 miles of range.
  • It's unlikely that Toyota will ultimately employ Tesla's battery design, which uses thousands of small commodity battery cells. “The whole battery envelope will be different,” Bernas said.
  • Toyota is considering body changes to improve aerodynamics, reduce weight and possibly change wheel size to maximize driving range.

Watch the video below and let me know what else would you like to know. Submit questions below, and I’ll do my best to get the answers from Greg or somebody else at Toyota/Tesla.


· · 7 years ago

That's what I thought, the timeframe was so short, they had no other choice than to use off the shelf components, I mean from the roadster. But I estimate that a RAV4 with a V6 has a GVWR some 1500 pounds heavier than a Tesla roadster, so it needs totally different electronics to adapt the motor's torque curve to the heavier weight, and regen has to totally recalibrated.

Interesting to learn that Toyota hasn't made up its mind on using commodity cells. I've got the feeling that nothing is decided yet, and I'm surprised they stick to the 2012 launch date.

· James Davis (not verified) · 7 years ago

There are several supercharge batteries being designed for production; liquid metal, and liquid salt for instance. Why don't Telsa and Toyota check these batteries out and start manufacturing them for their electric cars?

· kevin (not verified) · 7 years ago

Great job on the interview Brad!!!!!!!

· · 7 years ago

Thank you, Brad, for the informative interview! I'm happy that Greg seemed very willing to share information.

From the tone of the conversation, I suspect that a 100 mile range is the starting point, and that the production vehicle might do significantly better, say 150 miles. It's of course always better to start with lower expectations, then over-deliver.

I'd still like to know whether Toyota is considering the possibility of offering a part-time 4x4 option on this EV SUV. I don't think you'd want full-time all-wheel-drive due to the continual range hit. But having the ability to apply power to all four wheels would certainly help for those of us who deal with both hills and snow. In my case, I'd like 4x4 capabilities even if I never use them, mainly to avoid the overly rigid chain requirements that are enforced in California's mountains. (A car with FWD and good tires is usually fine, but not if you're from LA or OC and have no experience driving in snow.)

· · 7 years ago

Thanks guys. I'll continue to collect these questions and pass on to Toyota soon.

@abasile - Not sure about "significantly better, say 150 miles," considering that the the RAV4 is not a small car.

· · 7 years ago

What is the pack capacity of the original RAV4 EV? It may be possible to overcome the higher weight of the modern RAV4 chassis with a more efficient electric motor and controller?

I think weight is less important than aerodynamic drag. Because weight gives you better coasting (so you regain some of the energy potential), whereas drag is a total loss.

A 30-40kWh pack could deliver 200 or more miles, I think. The Illuminati Seven (from the X-Prize) has an effective pack capacity of around 32.5kWh, and they drove it nearly 200 miles with roughly 6% charge left:


The Seven weighs a little less than 3,200 pounds, and has a Cd around 0.23 and seats 4. And it accelerates 0-60 in less than 10 seconds (now that they have removed the clutch, which is the cause of them getting knocked out of the X-Prize).

I'm looking forward to the next couple of years, with all these EV's coming out! The Honda Fit EV and the Scion iQ EV are at the top of my list...

Sincerely, Neil

· · 7 years ago

Nicely done Brad. I am looking forward to more information on the RAV4 EV. It is exactly what I would like to buy. If they could deliver 125 MPC, and keep it under 40K before incentives than that would be great.

I do wonder what Toyota is really getting from Tesla as opposed to just engineering this completely on their own. It doesn't appear that they will be using much of Tesla's technology and they aren't going to let Tesla build them at the Nummi plant.

· · 7 years ago

Hey Tom - I believe you're right. The relationship is more about Toyota's desire to borrow from Tesla's "the spirit of entrepreneurship," than it is about engineering or production. You can cast it aside as marketing spin, but it's kinda cool. Two companies, one old and big and the other new and small, keeping lines of communication open to develop a new EV--and see where it all goes. I'll all for an all-electric small SUV or wagon, to deliver the most functionality in a gas-free way. The space is going to get more and more interesting.

· · 7 years ago

I just got a ticket this morning (first one in 16 years!) for driving our Prius without snow chains on the wheels. Never mind that I was driving safely, had no problem with the conditions (2" of fresh snow last night, which was plowed), and had chains in the car. Newbie highway patrol officer, I think. Maybe they assume Prius drivers are clueless in snow...

So, to reiterate, I *really* hope Toyota makes a RAV4 EV with 4x4 capabilities! Keep the chain enforcement guys off my back! :-)

· · 7 years ago

My curiousity was peaked by Greg Bernas being called the project chief engineer. Since he didn't seem to know the Roadster battery capacity I infer he is not a Tesla transplant to Toyota.

There is a story here I'd like to hear more about. Along the same lines, is the important R&D occurring in the US or Japan ?

· SnowBird (not verified) · 7 years ago

If they can get at least 50 miles range in a cold weather and an AWD, sign me up!

· Cezar Puica (not verified) · 7 years ago

I own a Prius from 2004 and my wife and I barely wait to buy this 2012 RAV4 EV! In addition, I am a senior mechanical design engineer for a big corporation & former commercial pilot, and I strongly suggest the followings (in the order of importance):

1. A radical new much more FUTURISTIC & modern aggressive external/internal design (Toyota please go beyond the Koreans bold new design or Nissan Juke), with a lower aerodynamic drag coefficient than now.
2. Put the radio scan button on the steering wheel! (I suffered from that when on my Prius need it to move my hand from the steering wheel and my eyes from the road hundreds of time per trip away from home area to reach for scan radio button on the center console scanning for next radio station in new areas I traveled away from home.
3. Bigger LCD screens on Navigation & other displays (use more neon deep Blue or even Green combinations, stay away as much as possible, except warnings, from red & yellow).
4. Go sophisticated & diversify with the instruments digital displays, use the whole dashboard length not only a small & restricted area, inspire from modern ergonomic aircraft cockpits large clear designs!
5. Lithium battery or better.


· Tom Franklin (not verified) · 7 years ago

I would like to see it have 50 miles up-hill capacity on the battery in AWD mode. That range at highway speeds and cold weather is what it would take to get from Denver to the ski resorts. Anything less than that, and the car would not let me avoid having a second car for mountain trips.

· · 7 years ago

Tom: I hear what your saying, I want a small 4wd EV myself. You're going to need to be a bit more specific though. How steep are we talking? Will you have three other passengers, plus 250lbs of gear? Are you looking to do this in sub-zero temperatures, or are we talking 30 to 40 degrees outside? These are very important questions and will have a great impact on the cars range.
If you plan on doing a lot of this kind of driving (4wd, highway, very cold climates) you might be best suited with a plug in hybrid or EREV type of 4WD (Yeah I know, none exist at the moment) I'm really more of a pure EV guy myself, but there are times and conditions that the pure EV doesn't work as well, and long trips at highway speeds up steep grades in the cold with snow on the ground is really as bad as it gets for an EV.

I get a good deal of snow where I live(this year it's been nothing but snow!) and driving in the snow does use more energy, even without 4wd.
I'd love a RAV4-type of vehicle that was a plugin with range extender like the volt for this kind of driving. I know it would probably be an expensive vehicle, but it would be perfect for my winter driving needs. Giving me the zero emission driving I want for most all of my daily driving(my wife's daily driving), but the ability to go on those long distance ski trips I desire. Of course my other vehicle would be a pure BEV for commuting, errands and such.

· · 7 years ago

@Tom Franklin: "Up-hill capacity" obviously depends on the amount of elevation gain. From Denver, it's about 50 miles up I-70 to Loveland Ski Area, just before the Eisenhower Tunnel. The elevation gain is 6000'.

With the LEAF, we've calculated that the additional energy to ascend 1000' should be under 1.5 kWh. 6000' translates to an additional 7.5kWh, on top of what it would take to drive the 50 miles on flat ground. It might also help that there's less wind resistance at altitude.

Driven very conservatively (maybe 55mph or slower), I think that even a current LEAF with a full charge could make it up to some of the ski areas. That's assuming mainly dry roads and a warm battery pack (it should warm up somewhat from the climbing). I'm hoping somebody with a LEAF tries some real mountain climbing soon to give us real data.

· · 7 years ago

With the Tesla, the general rule of thumb is to subtract 1 ideal range (240 mile full range for Tesla, 100 mile for Leaf) mile per 100 ft of elevation gain on the ascent but expect to gain that back on a descent.
What this means is that if you're driving south on I-5 from the Central Valley of CA where the elevation is around 300 ft and planning to ascend the Grapevine Grade over the Tejon Pass (elevation 4160 ft) for a 3900 ft climb, you'll need 39 miles of extra (above the flat drive range) ideal range to get to the top but you'll recover most of that extra 39 miles by the time you get to the San Fernando Valley outside LA.
You'll need more range with heavier cars.
Snow, of course, will impact your flat-land efficiency significantly as well.
I think Tom's right that an EREV makes a lot of sense if you'll be doing a lot of recreational driving in snowy mountains. Not only will the ICE give you longer range, it's waste heat may be usable to help keep you comfortable.
Now, will someone make me a high-clearance, rugged, 4WD, Diesel EREV so I can replace my Xterra?

· · 7 years ago

@ex-EV1: Losing one "ideal range" mile per 100 ft. climbed seems high, about double what I was expecting. Assuming 233 Wh/mile for the Tesla, that would be 2.3 kWh extra for every 1000' of climbing. Could this be due to inefficiencies in the batteries and drivetrain? Or is that "rule of thumb" overly conservative?

Here's where the estimate for the LEAF came from (actually 1.3 kWh/1000'): http://www.mynissanleaf.com/viewtopic.php?f=24&t=309&p=6025

Also, whenever potential energy you "store" by climbing, you are still going to lose a significant amount in regen, due to friction (tires, wind, etc.) and battery charging/discharging losses. I know with the Prius, it's been estimated that you can reclaim roughly about 50% of your potential energy by using regenerative braking on downhills. Maybe it's somewhat better with the Roadster.

· · 7 years ago

ex Ev1 said: "Now, will someone make me a high-clearance, rugged, 4WD, Diesel EREV so I can replace my Xterra?"

I will be first on line for that ex, you can have the second one.

· · 7 years ago

Regarding downhill driving: you come out at worst case, consuming zero energy on the downslope from just coasting down the hill with no motor running. An ICE is always idling so it's wasting gas, even on the downhill. At the bottom, you're back to flat land driving estimates again which are pretty easy to predict.
If you could just freewheel down the hill, all of your potential energy gained on the uphill would be dumped into kinetic energy and you'd be going very fast at the bottom, without air and tire drag, you'd expend no energy to return to your destination.
In the real world, you have air drag and that increases with the square of your speed so at some point you can't store any more of that potential energy as kinetic energy. At that point, you might as well use regen to capture it instead of losing it all to air drag. There isn't much you can do about tire drag except get a lighter vehicle or use lower resistance tire but that's the same on flat or hills.
If, as in most cases, you can't just use kinetic energy because you have to slow down on curvy descents. Again, regenerative braking will allow you to recoup some of the kinetic energy that you have to shed to keep your speed down. Therefore, at the bottom of the hill, you'd have some kinetic energy left over from the descent and a fraction of what you had to shed to slow down back in your battery. This may or may not be enough to handle your flatland drive back to your destination.
A good rule of thumb (and yes, my rules of thumb are very conservative) on freeway descents where speed isn't an issue is to let your car freewheel up to about 70 mph, and use regen to keep it around 70 mph (Darell may have a better number for the RAV4EV but 70 isn't too bad). With the Tesla Roadster, you can actually set the cruise control for 70 mph and it will do the work for you :-) Above 70 mph, your wind drag probably loses more kinetic energy than your regen does so you might as well start putting it in your battery.

· · 7 years ago

@ex-EV1: Our mountain area lends itself to *lots* of regen on curvy roads, which I have used to great advantage in our Prius compared to a standard ICE car, widening the gas mileage gap. Having a larger battery (as in a LEAF, Tesla, RAV4 EV, etc.) would allow much more energy capture on longer descents.

As for maximizing efficiency on freeway descents, my observation is that, up to some upper limit like 70mph, it only makes sense to maximize kinetic energy (speed) if you are nearing the end of a descent and wish to use that momentum to help with climbing the next hill or to glide as far as possible. Otherwise, especially on longer descents, you might as well use regen to keep your speed as low as safely practicable, and put more into the battery.

As for the new RAV4 EV, I reiterate my desire to see Toyota build it with a 4WD option. It seems to me that the incremental cost of adding 4WD/AWD to an EV would be less than in an ICE vehicle. Mechanically, I think basically all you'd need to add would be another electric motor connected to the rear wheels. The additional weight should be very modest, and the rear motor would only need to be powered when circumstances demand. The real work would be in the software.

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