# Motor size for electric vehicle?

If I was building an electric vehicle out of a light sedan, how many horsepower should the electric motor be? I want it to go around 65 MPH, and I do not care about acceleration (should still be within reason, though). The car is just a normal car, around 2000 LBS. A little more. DC Motor.

Thanks!

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• John W
Lv 7

The Urba-electric from the 70's had a 10 hp motor and had a top speed of 55 mph. The freeway speed limit was 55 mph back then they couldn't say that it had gone faster on public freeways. Later, they said that the top speed was 60 mph.

As a child, I always wanted to build an Urba-Electric and I still have that issue of Mechanix Illustrated though it's so well thumbed that it's literally fallen apart at the spine. I also always wanted to build a Weekender yacht, and earth sheltered homes, and thermal envelope homes, and a Quickie plane etc.

If you don't care about acceleration, you could probably get by with just 15 or 20 HP, the acceleration won't even be too bad as electric motors have enormous amounts of torque. Usually microcars are designed with motors in the 10 HP to 40 HP range. I believe that the Morgantown PRT which carries 12 people operates on just 70 HP.

If it's just about transportation, you don't need a lot of HP.

Unfortunately, the horsepower (HP) rating system for electric motors is way different than for internal combustion engines. Electric motors are typically given 2 HP ratings: one for continuous operation and one for peak output. The continuous operation HP value for the motor in my 3600 lb Mazda electric is only 17.5. But "continuous operation" is really saying how much power can the thing produce without getting hot. The peak HP value is how much power it can put out, heat ignored. The peak value is generally about 3 times that of the continuous HP value.

Internal combustion engine horsepower is measured on a test stand under perfect conditions. They ramp up the rpm to find the max HP value and report that. It's rarely where you'll ever operate a car, even if you could keep your engine in the same perfect shape.

When looking for electric vehicle (EV) motors, remember that you're likely going to see their power values expressed in watts where 746 watts is 1 horsepower.

My truck's motor is model 203-06-4001 Series Wound DC. The manufacturer used to be called "Advanced DC" but I hear they've changed their name now. Many catalogs etc still call them by their old name.

If you used the 203 in a 2000 lb car, say with 108 volts or so, it should really be quick. Keeping the car light is really important. Mine at 3620 is so heavy that the acceleration is poor.

Source(s): http://www.evalbum.com/2191 about my truck http://www.evconvert.com/tools/evcalc/ this is a web-based calculator which predicts the speed and range of a car your considering. It's a little tough to learn but worth the effort. "Build your own Electric Vehicle", Seth Leitman and Bob Brant, 2009 is a goldmine about how EVs work, what matters, what doesn't. A simpler book "Convert It" by Michael Brown goes more into the mechanics of how to convert a car to electric. http://www.kta-ev.com/ a good place to buy EV motors etc. Wistar can help you pick the right motor size even if this is just a school project.
• Nata T
Lv 6

do you want 0 to 65 mph in 3 seconds or 3 hours? a Tesla has a 200 HP motor and a electric go cart has 15 HP. To beat a prius in the 1/4 mile, you'd need about 100 HP. A 60 HP would get close to hitting 65 mph, it would take about 5 miles.

• Anonymous