# Does an electric car need a transmition? **URL:** \ **Category:** Factual Questions\ **Created:** [October 19, 2007, 3:55pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305 "2007-10-19T15:55:24Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [October 19, 2007, 3:55pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/1 "2007-10-19T15:55:24Z")
A few weeks ago, I was out drinking with some of my old school buddies, when one of them said that an electric car didn’t need a transmition. He said that when an electric car changes speed it just runs faster. The rest of us thought this was proposterous, but not being engineers we didn’t have the ability to prove it to him. ---
**Author:** ![Mr.Slant](https://avatars.discourse-cdn.com/v4/letter/m/c57346/32.png) [@Mr.Slant](https://boards.straightdope.com/u/Mr.Slant)\ **Post date:** [October 19, 2007, 4:00pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/2 "2007-10-19T16:00:05Z")
Electric cars DO have a transmission, by definition. That being said, automotive electric motors, having gobs of torque available at low ‘RPM’, have little need for multiple forward gear ratios. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [October 19, 2007, 4:05pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/3 "2007-10-19T16:05:42Z")
[The Tesla](http://www.teslamotors.com/efficiency/how_it_works.php) is the only one I know anything about\*. It has no traditional automobile transmission. It needs no engine oil or transmission oil. It does have some form of tranny between the electric rotor and the wheels and two forward speeds. Here is a partial cite: > [@](#): > > But the comparison doesn’t end with the counting of moving parts. The engine and transmission of a conventional car also need lubricating oils, filters, coolant, clutches, spark plugs and wires, a PCV valve, oxygen sensors, a timing belt, a fan belt, a water pump and hoses, a catalytic converter, and a muffler — all items requiring service, and all items that aren’t needed in an electric car. Jim - Only because I would love to have one. ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [October 19, 2007, 4:06pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/4 "2007-10-19T16:06:03Z")
This example car has a transmission but from the article it seems it is only used for switching between forward and backward. So it would seem it is possible to forgo the different gears for drive. Electric motors do have a wider range of speeds at which they operate well. Most significantly for cars they have good torque at zero RPM so they don’t need a clutch to start. They obviously need some sort of transmission to get the power to the wheels but you may only need to switch between forward and reverse and not need things like first, second etc. Which a lot of people refer to as the transmission. So I would say your friend is basically correct. > **[How Electric Cars Work](https://auto.howstuffworks.com/electric-car1.htm)** > > Sales of electric cars keep soaring and the technology just keeps getting better. So how do electric cars work and just how green are they? ---
**Author:** ![WarmNPrickly](https://avatars.discourse-cdn.com/v4/letter/w/d78d45/32.png) [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)\ **Post date:** [October 19, 2007, 4:16pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/5 "2007-10-19T16:16:10Z")
Wow! Cool! That’s why I asked here. 🙂 ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [October 19, 2007, 4:23pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/6 "2007-10-19T16:23:39Z")
[QUOTE=Mr. Slant] Electric cars DO have a transmission, by definition. [/QUOTE] I assume you’re trying to point out the difference between “transmission” and “gear shift mechanism”? But electric cars can be driven by hub motors, and I don’t think there’s anything there that can be called a “transmission” by any definition. ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [October 19, 2007, 7:01pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/7 "2007-10-19T19:01:39Z")
[QUOTE=scr4] But electric cars can be driven by hub motors, and I don’t think there’s anything there that can be called a “transmission” by any definition. [/QUOTE] Can be, but what mass market current electric (or even hybrid) uses hub motors? Not disputing that this isn’t a good idea, just pointing out it’s not done yet. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [October 19, 2007, 7:36pm UTC](https://boards.straightdope.com/t/does-an-electric-car-need-a-transmition/423305/8 "2007-10-19T19:36:25Z")
In addition to what has been mentioned upthread, an electric motor can achieve several “gears” by changing the way multiple windings are connected. One connection gives tremendous torque at zero-low speed for starting, and other connections yield higher speed at less torque. This is used to great advantage in railway applications. Google “traction motor” for lots of detail. An electric car can also vary “gearing” by switching the way the cells in the battery are connected. By connecting low voltage strings in paralell, low voltage battery with tremendous current capacity is obtained…just the thing for starting from a stop. Placing the cells in series gives high voltage at lower current, which is ideal for cruising. A switching type speed controller can achieve similar effects without the need to actually change the cell connections. Finally, if a hybrid has no provisions for the engine to mechanically drive the wheels, then the excitation to the motor driven generator can be varied to give an effective gearing change.