# How can I tell if a motor is powerful or weak



## subcooledheatpump (Mar 5, 2012)

Power is a product of voltage and current 

Volts times amps equals watts (V*I=P) 

Motors vary greatly but the power of a motor is determine by it's voltage and it's current abilities. Their voltage and current ratings are usually marked on their sides, but some motors may require online research to find their ratings 

If I can apply 750 volts to a motor and 1 amp flows, then I have a 750 watt motor. 

If you have a 44 volt motor and it allows 100 amps to flow then you have a 4400 watt motor, or 4.4 kW motor. At the same time you could have an 88 volt motor that allows 50 amps to flow and it would give the same output. 

So voltage is only one factor

Larger motors usually have higher ratings. For an electric car, you need to determind first what battery voltage you'd like to use. Higher voltages means higher efficiency since the current is lower, therefore less heat loss. Higher voltage however, also means a greater number of batteries and connections that could go wrong. 

Lower voltage means fewer batteries and fewer connection that could go bad, but also higher current which means more heat loss. 

These things you'll have to decide on your own, but there are conversion kits that can give you a general idea of what is reasonable. Alot of conversions are below 200 volts with up to 1000 amps. A few people do high voltage conversions with 600 + volts. You'll have to jump in where you feel comfortable. If you are new to EVs I wouldn't recommend going over 200 volts


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## rickyd123 (Mar 26, 2012)

I'm a little confused and not that experienced with electrical jargon. If I'm understanding this correctly I'll put not the 12 volts from the battery, but 44 from the controller. Along with that 44 volts will be 100 amps. ( This may be wishful thinking or crazy thinking. I'm just looking for the relation.)
I'm trying to think in my limited terms. Isn't there a correlation between amps and watts. If I put 100 amps in shouldn't I get something like 10,000 watts out. Ok now I'm more then a little confused. I think I may need an electronics guru.


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## major (Apr 4, 2008)

rickyd123 said:


> I'm a little confused and not that experienced with electrical jargon. If I'm understanding this correctly I'll put not the 12 volts from the battery, but 44 from the controller. Along with that 44 volts will be 100 amps. ( This may be wishful thinking or crazy thinking. I'm just looking for the relation.)
> I'm trying to think in my limited terms. Isn't there a correlation between amps and watts. If I put 100 amps in shouldn't I get something like 10,000 watts out. Ok now I'm more then a little confused. I think I may need an electronics guru.


http://www.diyelectriccar.com/forums/showthread.php?t=669&redir_from=668 Read this please.

The answers you seek may be found in this section. http://www.diyelectriccar.com/forums/showthread.php?t=6535


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## rickyd123 (Mar 26, 2012)

Ok. I've been told to read this before and I have. It's still over my head. I'll keep reading hopefully it'll sink in. Thanks


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## subcooledheatpump (Mar 5, 2012)

It's all really simple, you're just overcomplicating it. 

Volts times amps equals watts. Thats all it comes down to

A motor controller only regulates the amount of watts that comes out of a power source, like a battery. 

Think of a motor as a water wheel, and a motor controller as a water valve. All a motor controller does is turn the water flow on or off. If you've got more water pressure and a larger volume of water, comparatively, then you will get more power at your water wheel. 

If one motor is rated 12 volts and 10 amps, it will then be a 120 watt motor. 

if another is rated 12 volts and 100 amps, then it would be a 1200 watt motor. 

Like I said earlier, each motor has it's own rating, but all you need to do to know how powerful it is, is multiply it's volts and amps. volts times amps equals watts. 

volts alone doesn't equal power, and amps alone doesn't equal power, it's both. 

Good luck


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