Vocis launching demo EV with 2nd gen multi-speed transmissio

"Vocis launching demo EV with 2nd generation multi-speed transmission; projected 15% improvement in vehicle efficiency"

Via Green Car Congress:

http://www.greencarcongress.com/2013/04/vocis-20130430.html" onclick="window.open(this.href);return false;

So, seeing another announcement of multi-speed transmissions for EVs,

http://www.greencarcongress.com/2013/07/4sed-20130725.html#more" onclick="window.open(this.href);return false;

I'm wondering if this is something it's time to reconsider. Offhand, the original version of the Tesla Roadster is the only production BEV I can think of with a multi-speed transmission, and they pulled that owing to reliability issues and changed to single speed with some electronic magic. OTOH, lots of EV conversions in the '80s and '90s kept their manual transmissions.

ISTM that the efficiency gain at freeway speeds for cars intended for other than urban use, typically claiming 15% or so, may be worthwhile even allowing for the extra complexity. I suspect a multi-speed transmission is still far cheaper, lighter and smaller than putting in extra batteries for the same range gain, and acceleration performance for passing would also be improved (although Chevy seems to have found a work-around with the Spark EV). I don't think it's worth it for the city cars, but I could see a two-speed transmission, with low for 0 to say 50 mph, and high for 45+ with efficiency optimized for the 65-80 speed band as maybe being worth it for those BEVs with enough range to give them some road trip potential. Opinions?

^ Well, only to say that I agree entirely. Others may find the complexity not worth the gains (in the back of my mind, I think we've had this discussion before).

If nothing else, I think its clever that they took the idea of a DSG and the advantages of an electric motor and rolled them up together.

The inverter would be interesting, because to take full advantage of this tech, it needs to be capable of sending full power to either motor and also be capbable of running both motors at different speeds. So you essentially need two motor controllers and two motors, both capable of handling full power.

mwalsh said:

^ Well, only to say that I agree entirely. Others may find the complexity not worth the gains (in the back of my mind, I think we've had this discussion before).

Click to expand...

You're right, but I missed it:

http://www.mynissanleaf.com/viewtopic.php?style=3&f=4&t=12364" onclick="window.open(this.href);return false;

GRA said:

ISTM that the efficiency gain at freeway speeds for cars intended for other than urban use, typically claiming 15% or so, may be worthwhile even allowing for the extra complexity. I suspect a multi-speed transmission is still far cheaper, lighter and smaller than putting in extra batteries for the same range gain,...

Click to expand...

I think calling this a "multi-speed transmission" is a bit of a misnomer since it requires two traction motors, much like the Chevy Volt uses two traction motors. So, really, they have added not just a transmission but also another traction motor and its inverter. All this to gain "up to 15% improvement" at highway speeds. Since the efficiency of the LEAF is above 85% at highway speeds, I do not think there is 15% to be gained.

My guess is that you may see this type of "transmission" in sports cars or delivery vehicles where the performance makes a difference, but not in everyday EVs.

Hello,
I agree with pretty much all of what's been said. Before I signed on for the leaf in 2010 I had planned to build an EV out of a 1995 Toyota Tercel. My design included dual motors driving a reduction gear via a planetary gear set. Torque and efficiency figures were impressive, besting my 5.0L mustang at all speeds.
I decided on the leaf because it was only $5k more expensive and it saved a year or more of work. Would still be a fun project though.