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What HP electric motor does my conversion need?

by Denny
(Oklahoma)

Feelin' the Horsepower?

Feelin' the Horsepower?

I am just starting to look at building an electric vehicle. I have the mechanical know how but lack the electrical know how. What HP motor should be used?

Hi, Denny!
You want numbers, don't you?
First of all, it depends on how many volts you run the system at. Any given motor can deliver more or less horsepower with more or less voltage. A medium size, typical DC motor adequate to move a Mustang or Porsche along at a zippy clip pulls 120-144 volts from the batteries, and gives something like 30-40hp continuous, 70-80hp peak. The larger sized DC motor, similar voltage system, gives more like 40-50hp continuous, 100hp peak.

That's probably lot fewer than you were thinking, given your experience, huh?
This is why: Internal Combustion Engines, or ICE-machines - hehe - use most of their horsepower to get from 0-45 mph. Once you get up to speed, most of the horses in your ICE machine are standing around in the pasture, doing nothing but eating up all the grass.

Oops, took that metaphor too far, didn't I?

On the other hand, an electric motor (especially the DC motor) is very clever at getting from 0-45 mph effortlessly. Think of an electric drill, and all the torque it delivers when you first pull the trigger! Yes, it does that with the car, too. That's why we fall in love with the feel of electric drive, and get that "EV grin".

Then once you get up to speed, those horses go on vacation as well, just like in the ICE-machine; but with an electric motor, they don't eat. They just stand there waiting for orders.

Less is more, Denny; )

Regards,
Lynne


P.S. Read more about AC motors vs. DC, or see which type of motor is most popular in EVs.





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How Many Amps Needed?

by Jeremy
(United States)

Amps

Amps

How many amps does the average electric car need?

Hi, Jeremy -
Jim Husted from Hi-Torque Electric says:

"This depends on what kind of speed and performance you’re looking for. I’m someone you believes that even Grandma will break the power out of the box every now and then if given the option (if not, put her in an EV and she will!)

That said, I advise planning on a 120 volt 500 amp system as a base. This would net most vehicles freeway speeds and traffic keeping performance, with a higher voltage and current if you want Grandma to have a really good time borrowing your car.

As a general rule, I like to use the "1000 watts to 1 HP" rule. A watt is amps times voltage. This will account for heat and friction losses and net you a better prediction of what you’ll actually get in real life. It comes down to watts not amps when looking at this question in that 10V @ 100A is the same as 100V @ 10A both being about 1 HP. This is why people use as high a voltage as reasonable being they can keep current lower and still produce HP."

Regards,
Lynne

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