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#### Ian J.

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it's my impression that you can in principle feed them any voltage. it's not like a 24V motor will melt if you feed it 36V. volt in principle can't hurt it BUT volt motivates current to appear. the higher voltage the more current will tend to appear and current can destroy a motor. to really understand it you have to understand the physics concept of work. nature has a magical way of ensuring you pay for the work a motor does. work is the force (or torque) applied over a distance. if you apply force and nothing moves you don't have to pay for it. just like a paper weight is free force. that force (or torque in the case of a motor which is just force going in circles) comes from the current and the work done during rotation is paid for with voltage. you can imagine a worker that only does as you pay him.
this means for instance if the motor is stalled, let's say up against a wall and can't turn even a little voltage will make the current rise a lot because there is no rotation and no work done. you pay voltage and it tries to make work. when it can't the current rises dramatically, in theory infinitely if it weren't for resistance in the wires. but going 100km/h it wants a lot of voltage to maintain a current level. if you don't feed it the current will drop to the level you feed it. nature has a 'magical' way to make sure you get exactly what you pay for.
so voltage motivates current in a balance with how much work the motor does. slow rpm it's easy to motivate current to appear. high rpm it takes more voltage.
a motor's limit is a current limit and not a voltage limit BUT there is an indirect voltage limit because the motor can only handle so high an rpm for mechanical reasons.
let's say a motor is rated at 150A continuous and 5000rpm and that at that speed it takes say 100V to keep the current level at 150A. so you might say that 100V is the max for that motor BUT a motor can take more current briefly so let's say you want it to peak up to 450A then you need 300V to keep that level at 5000rpm. that would be 450Ax300V=135kW (or around 150HP after efficiency)
the power formula you can use is

P = T x w = T x Hz x 2 x Pi where T is torque, w is rotational speed in radians per second, Hz is revolutions per second, Pi is 3.1415...

torque is a direct result of current in the motor and that relationship you can look up in a spec sheet for the motor. a current torque graph (not always available) here are some example curves: http://www.zev.dk/misc/torque-curves.gif

once you have that for your motor you can use the above formula to roughly figure out how much voltage your desired performance will take at the motor's max rpm. it gives you a power value for your chosen current which you can then get voltage from using

P = I x V

where I is current and V is voltage. P is power.

IIRC
This is awesome! I’m going to throw this formula into an excel page and noodle around with it to see what motor/battery combo I need for my
‘65 beetle to go 70-80mph briefly but be able to cruise at 60 or less for a 100 mile range

#### Duncan

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6,238 Posts
This is awesome! I’m going to throw this formula into an excel page and noodle around with it to see what motor/battery combo I need for my
‘65 beetle to go 70-80mph briefly but be able to cruise at 60 or less for a 100 mile range
Something to bear in mind is that the current limit is time related
My motor is "rated" at 200 amps - that is the one hour rating - basically it will not overheat at 200 amps
HOWEVER that is at about 1400rpm - at say 4200rpm the built in fan is putting a lot more air through the motor

AND - an hour is a long time

In my car I feed that motor with 1200 amps - and it survives as I can only feed it for a few seconds before I have to lift off

I'm running a 340 volt battery

#### Tommy McL

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Dear all in this amazing site,

Greetings and congrats to all those who who have posted. Every point of view is information for others like me who have been tested positive on "I want to build / convert an EV".

I have the chance to purchase 3 different motors from one forklift (see attached photos) for \$250, ready for collection.

If I get these motors, what would be the "sweet" conversion voltage to run them and how heavy can the total build be? Planning a budget conversion and keeping the shift transmission.

Any reviews / replies appreciated.

Cheers, Tommy

PS: The second motor is rated at 180 amps, as the photo is not clear...

PPS: any suggestions for a Siamese layout before the tranny are welcome (Space issues discussed later)

#### JRP3

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The two motors attached to pumps may be female shafts and would likely be useless.

#### Tommy McL

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Hello again,

This time I have the chance to get a Motor with the same specs as the motor in the attached photo.

(I hope the original poster of the image does not mind me using it).

The "No E 534671" is different, the rest is the same.

Any pros and cons? What would be a reasonable price to pay for it?

Any input from the members out there is very welcome

cheers, Tommy

#### brian_

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This time I have the chance to get a Motor with the same specs as the motor in the attached photo...
That's not a "forklift" motor, or a brushed series-wound DC motor (which is what people usually mean by "forklift" motor). This isn't the thread to discuss it. Why not post a separate thread (in this same section of the forum)?

In your new post, mention that is a Siemens 1PV5135-4WS14; there is lots of experience with them. Or just search the forum for "1PV5135-4WS14".

#### Tommy McL

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Oops...

what brian_ mentioned is correct. Many thanks. Also thanks for the suggestion.

If a Forum Administrator can relocate my post, I would be thankful. No point in complicating this thread.

#### brian_

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If a Forum Administrator can relocate my post, I would be thankful. No point in complicating this thread.
Good idea, but there is no longer any active forum administration. It would be easier to just create a new thread, and perhaps edit out the contents of the posts in this thread (since members can't delete even their own posts in the current forum software).

#### Stephen the Obdurate

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I'm trying to find a smallish motor 1/4 to 1/2 HP and 24v to 28v (12v would be OK but would double the current) I won't exceed 25 mph on the flat. I haven't found any part numbers or sources. Any suggestions?

2561 - 2569 of 2569 Posts