FAQs
My wife doesn’t drive a stick, why don’t any of the EVs have an automatic transmission? Do I have to use an AC motor in order to keep the automatic transmission?
You can make an automatic EV with DC just as easily as you can AC. The trick with an automatic is you need to have the motor slowly spinning ALL of the time to keep the hydraulics pumped up. Maybe you could find an old donor car that uses a CVT transmission, I don’t think they need the hydraulic pressure and they are automatic.
There are some AC motor setups that have been designed to replace the transmission as well, which might be what you are referencing. No reason you couldn’t run a DC motor with the same gear box, that is if someone will sell it to you and you can adapt it to the spline.
Depending on your driving you don’t necessarily have to shift that much, if at all. I only did city driving on my EV (under 40mph) and pretty much left it in 2nd gear all of the time.
Lee Hart posted the following on the EVList a while back:
If it’s a budget conversion, I’d say keep the automatic. Let the electric motor idle, just as it would with the ICE. Use a motor with a rear shaft, so you can put a pulley on it and drive the old alternator and other accessories (air conditioner, etc.).
Idling wastes a little power; it will generally draw 1-2 amps from the propulsion pack when stopped. This is low enough that you could leave it idling for a day or two before it discharged the pack.
Automatics that don’t have a locking torque converter are a little less efficient, so they will cost you 10% or so in range.
I have a 1988 VW Rabbit Cabriolet convertible that I would like to convert into an EV. The only problem is that it has an automatic transmission. Any possibility of finding an AC motor that could replace the transmission on this particular car? ... or how well would my car operate if I keep the auto transmission? Thanks.
I have a 1993 nissan 240sx. And i have the starter hooked up to a switch. This is so that i can turn it off at stops and goign downhill, and start it when needed. Without getting to as to why I do it, I leave the car in drive all the time. when the light turns green I just start it and the engine will crank then as soon as it gets to about 700rpms it engages into drive and drives off.It will engage as low as 500rpms and the only problem is that if the motor has too much time to “speed up” then when it doesn engage you’ll burnout…if thats the case. there’s no problem with leaving it automatic other than a small delay from when the motor spins and your wheel spin. if you would like the transsmission can be locked to 1st or second gear by selecting L1 or 1 depending on the transmission. reverse will work. Park will too, something manual transmissions cant do with an electric motor.
Hey Joel, that sounds like a good idea.
I wish I’d thought of that years ago. Imagine a switch on the accelerator that starts the gas engine as soon as it’s even slightly pressed.
I know gas engines use something like three times the fuel (compared to driving) when starting, but it would still save quite a bit of money. The engine would start without even thinking about it.
Might be a bad thing too in a manual car.
There’s a few things that would need tweaking (ie: making sure the starter doesn’t try to start the engine while coasting at 60mph) but it could be a nice idea.
Lets look at some old race car technology. They sometimes use a direct hub in place of the torque convertor, which is why you would have to “idle” your motor. I’d like to try an auto trans, left in drive and take off in low with an electric motor. Although you’d want to choose a trans without a vacuum modulator and throttle valve linkage. (if that is possible)
A swith to cut/start the engine is a great idea. But bypassing the neutral saftey swith (so you can leave it in drive) is not. Your car could start in gear and take off on you. Also, it’s REALLY hard on the starter to start the engine like that, worse if it’s a manual and you’re starting it in gear. You’ll burn the starter out on no time. Starters are not cheap.
And if your car is like mine and you have hydraulic brakes, engine off = oh crap.
“And if your car is like mine and you have hydraulic brakes, engine off = oh crap”
This is a Vacuum Booster issue; you still have brakes just not the power assistance.
Can anyone recommend a good direct drive ac or dc engine setup that would effectively replace an AT tranny? Cars like the Tesla use one from ACPropulsion. Any others out there?
What exactly is a CVT transmission? Also, would a front-wheel drive car with an automatic transmission have one? I’m thinking about converting a 2003 PT Cruiser to an EV in the future (after I’ve paid off the loan).
Patrick.
A CVT is a Continuously Variable Transmission. the motor stays turning at a certain RPM but when you push the pedal a pulley moves further from the engine and axle pulleys and tightens up the belt. as the belt tightens the axle pulley speed increases thereby increasing the speed. if you need further info google CVT transmission.
Here is a link discussing diagnostics for vibrations with a CVT transmissions; it has some good information on which vehicles have them and pictures.
Pictures are good! I like pictures…
http://www.vibratesoftware.com/html_help/html/Diagnosis/Reference/CVT_Transmissions.htm
Thanks for the link Dan. I didn’t know that they had invented a two pulley CVT but obviously they have by the looks of the pictures. a good example of a CVT transmisssion is the new John Deere mowers. instead of a 4 or 5 speed shifter they have an accelerator pedal and apparently these are attached to CVT transmission. they are very fun to drive at high speed(i clocked 9 mph on mine)
History of the CVT
“Leonardo DaVinci sketched the first CVT in 1490. Dutch automaker DAF first started using CVTs in their cars in the late 1950s; however technology limitations made CVTs unsuitable for engines with more than around 100 horsepower. In the late 80s and early 90s, Subaru offered a CVT in their Justy mini-car, while Honda used one in the high-mileage Honda Civic HX of the late 90s.
Improved CVTs capable of handling more powerful engines were developed in the late 90s and 2000s, and CVTs can now be found in cars from Nissan, Audi, Honda, Ford, GM, and other automakers.”
http://cars.about.com/od/thingsyouneedtoknow/a/CVT.htm
Also See: Variomatic
http://en.wikipedia.org/wiki/Variomatic
Why wouldn’t an overdrive unit work as a replacement for a transmission to extend range at higher speeds.
Why would you need a torque converter in this case? If you were to get rid of that, what other “hydraulics” would need to be powered?
There are virtually no automatic transmissions, bar the Power Glide, that have a low enough drag (or high enough efficiency) to justify having them; torque converter or not.
You cannot simply operate an A/T sans a converter because without hydraulic pressure (“engine” running ALL the time – even at idle) you can’t engage ANY gear.
The slight motor efficiency loss at low speeds (<35 MPH) of a single gear set-up more than outweigh any benefits of a transmission, any type of transmission.
The main reason that I’d want to use an automatic transmission is that if anyone else drove the vehicle they could just put it in park when they were done driving and I wouldn’t be worrying the whole time if they’d remembered to set the parking brake when they got out. Also not all vehicle Parking Brakes are equal…