Go Back   EcoModder Forum > EcoModding > Fossil Fuel Free
Register Now
 Register Now
 

Reply  Post New Thread
 
Submit Tools LinkBack Thread Tools
Old 07-24-2013, 11:15 AM   #1 (permalink)
Master EcoModder
 
P-hack's Avatar
 
Join Date: Oct 2012
Location: USA
Posts: 1,408

awesomer - '04 Toyota prius
Thanks: 102
Thanked 249 Times in 201 Posts
make your EV more efficient, with a multi-gear transmission

Electric motors have areas of operation where they are less than their peak efficiency, not unlike ICE's. The solution, modify the gear ratios in-flight (efficiently), of course. Tesla wanted to start with a two speed but didn't get the bugs worked out at those power levels I recon. The simplicity of direct drive is nice, but leaves a significant amount of efficiency on the table.

They claim 15% reduction in battery size (which translates into less weight and shorter recharge times)

Drive System Design: New three-speed transmission helps electric vehicles run farther, faster and more smoothly Automotive World

  Reply With Quote
Alt Today
Popular topics

Other popular topics in this forum...

   
Old 07-24-2013, 11:32 AM   #2 (permalink)
Master EcoModder
 
P-hack's Avatar
 
Join Date: Oct 2012
Location: USA
Posts: 1,408

awesomer - '04 Toyota prius
Thanks: 102
Thanked 249 Times in 201 Posts
while reading some of the comments on the tesla forum, it is disheartening to hear the rank distaste and outright misinformation on using more than a single speed gearbox.

Most are outright oblivious as to what makes a machine efficient as far as I can tell, but for most motors the efficiency is largely a function of load (true for electric and ICE), and a higher gear that provides more engine load is going to help at higher speed, and a lower gear is going to help with hills and acceleration, and just having some ratio options means smaller motors (easier to load) and batteries for typical driving.
  Reply With Quote
Old 07-24-2013, 11:50 AM   #3 (permalink)
Master EcoModder
 
P-hack's Avatar
 
Join Date: Oct 2012
Location: USA
Posts: 1,408

awesomer - '04 Toyota prius
Thanks: 102
Thanked 249 Times in 201 Posts
and of course if you are serious about an efficient series setup, you need to pay attention to how your EV motor uses that power as well.

Vocis is road testing a multi-speed EV transmission - HybridCars.com
  Reply With Quote
Old 07-24-2013, 12:38 PM   #4 (permalink)
Administrator
 
Daox's Avatar
 
Join Date: Dec 2007
Location: Germantown, WI
Posts: 11,173

CM400E - '81 Honda CM400E
90 day: 51.49 mpg (US)

Daox's Grey Prius - '04 Toyota Prius
Team Toyota
90 day: 49.53 mpg (US)

Daox's Insight - '00 Honda Insight
90 day: 64.33 mpg (US)

Swarthy - '14 Mitsubishi Mirage DE
Mitsubishi
90 day: 56.69 mpg (US)
Thanks: 2,471
Thanked 2,537 Times in 1,529 Posts
This is very true. In addition to downsizing your pack you can also downsize your motor as well. I looked into this when I was considering hybridizing my Paseo. I didn't have room in the engine bay for a large motor, so I had to eek out everything I could. Going through the gear box was the only way to achieve reasonable acceleration with the space I had to work with.
__________________
Current project: A better alternator delete
  Reply With Quote
Old 07-24-2013, 12:39 PM   #5 (permalink)
Master EcoModder
 
P-hack's Avatar
 
Join Date: Oct 2012
Location: USA
Posts: 1,408

awesomer - '04 Toyota prius
Thanks: 102
Thanked 249 Times in 201 Posts
just for a visual, I color coded a TDI bsfc chart in terms of lost efficiency from peak bsfc, the percentage losses are reasonably similar over much of the operating range.


compared to: (though this is a generalization, extreme low load is probably worse than indicated, i.e. https://www1.eere.energy.gov/manufac...s/10097517.pdf )
Attached Thumbnails
Click image for larger version

Name:	bsfc.jpg
Views:	552
Size:	89.6 KB
ID:	13506  

Last edited by P-hack; 07-24-2013 at 12:48 PM..
  Reply With Quote
Old 07-24-2013, 02:03 PM   #6 (permalink)
Master EcoModder
 
Join Date: Sep 2009
Posts: 5,927
Thanks: 877
Thanked 2,020 Times in 1,303 Posts
A transmission would also benefit regeneration.

regards
Mech
  Reply With Quote
Old 07-24-2013, 11:06 PM   #7 (permalink)
Master EcoModder
 
Join Date: Aug 2010
Location: Philippines
Posts: 2,173
Thanks: 1,739
Thanked 588 Times in 401 Posts
We've known for quite a while that EVs could benefit from multi-gear transmissions. What's been missing are transmissions that can take the power of something like the Tesla Roadster.
  Reply With Quote
Old 07-24-2013, 11:45 PM   #8 (permalink)
Master EcoModder
 
Ryland's Avatar
 
Join Date: Jan 2008
Location: Western Wisconsin
Posts: 3,903

honda cb125 - '74 Honda CB 125 S1
90 day: 79.71 mpg (US)

green wedge - '81 Commuter Vehicles Inc. Commuti-Car

Blue VX - '93 Honda Civic VX
Thanks: 867
Thanked 433 Times in 353 Posts
What is also missing is a transmission that can shift smoothly, without the sound of a gasoline engine and the vibration it's hard to tell when to shift an electric car, it's also hard to match motor RPM to wheel RPM so you increase the chances of grinding gears, these are small problems that could be taken care of with a very basic computer control and electronic shifting.
There are also transmissions that will handle the power, there are transmissions that will handle 1,000hp trucks and those have to deal with the vibrations of the engine!
As I understand it the area where Tesla had trouble is they tried to use a low cost, Geo Metro transmission and that blew up then realized that an over sized motor was cheaper then a transmission and made it simple.
  Reply With Quote
Old 07-25-2013, 12:22 AM   #9 (permalink)
Human Environmentalist
 
redpoint5's Avatar
 
Join Date: Aug 2010
Location: Oregon
Posts: 9,311

Acura TSX - '06 Acura TSX
90 day: 28.24 mpg (US)

Lafawnda - '01 Honda CBR600 F4i
90 day: 47.32 mpg (US)

Big Yeller - '98 Dodge Ram 2500 base
90 day: 21.82 mpg (US)

Prius Plug-in - '12 Toyota Prius Plug-in
90 day: 57.64 mpg (US)

Mazda CX-5 - '17 Mazda CX-5 Touring
90 day: 26.85 mpg (US)
Thanks: 3,231
Thanked 3,557 Times in 2,656 Posts
I should think simple economics will dictate the design of cars to come. If it's cheaper to include a transmission and related shifting technologies than to build larger motors and batteries, EVs will soon receive them.

In the race to be first to market with EVs, transmissions may have been dropped to speed the development process. Perhaps future iterations will include them, or perhaps the cost, complexity, and reliability are hurdles the transmission cannot overcome.
__________________
Gas and Electric Vehicle Cost of Ownership Calculator







Give me absolute safety, or give me death!
  Reply With Quote
Old 07-25-2013, 01:25 AM   #10 (permalink)
Master EcoModder
 
P-hack's Avatar
 
Join Date: Oct 2012
Location: USA
Posts: 1,408

awesomer - '04 Toyota prius
Thanks: 102
Thanked 249 Times in 201 Posts
we've never really seen inexpensive pico-second controller timing and position sensing applied to a transmission, at least I haven't. But it seems very possible to make a reliable, efficient, fairly compact, and smooth shifting sliding mesh transmission with some authority over the traction motor during shifts as needed. such a transmission can theoretically rpm match the motor actively and even wait for teeth to be aligned before sliding into gear, then reapply power smoothly (user defined), and all very quickly, and cheaper and more efficient than dual clutch.

  Reply With Quote
Reply  Post New Thread


Thread Tools




Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Content Relevant URLs by vBSEO 3.5.2
All content copyright EcoModder.com