How IS this possible???

[ash ketchum]

I bought a 12v motor yesterday which cost me 80 INR, which translates to 1.25$. It is the length(from the base to the tip of the shaft) of a AA battery and is 2x wider than one. Today, I tested it and here's the funny thing: I took a small wheel of an rc car, attached it to the motor, hooked it to a 12 volt battery(taken from a UPS so it can supply upto 50 amps continuously) and tested the current it took, it took MORE THAN 20 AMPS!!! HOW IS THIS POSSIBLE??? And, can I use this motor to make a low power pedal assist friction drive? Well, it got to more than 12x20=240 watts, so it MIGHT NOT be "low power".

 

[Hardergamer]

Have a look at the spec's and find out it's RPM voltage etc, as it is most likely too high RPM to use for a "friction drive" but.. you could get it to work sort of...but not for long, is it worth it?
It's the sort of small motor they use in a battery drill or fan, or use in some cheaper RC cars etc. "12v 20+ amps" get ready for some smoke :lol: just saying it will not last long :lol:

Good luck!

 

[cal3thousand]

20 Amps peak... what will it take continuous? I doubt it would be 20A

 

[CaliClouds]

I've used these motors in R/C projects before and they are in no way suitable for a bicycle. Sorry man. They will handle about 3 amps continuous with a very small load. Running 5 amps peak in an R/C truck the motors release the magic smoke somewhere between 1 and 30 minutes of run time. They are also brushed motors so longevity is not good.

 

[Sunder]

Said in pretty much other terms already, but brushless would basically be a short circuit if it wasn't for the magnetic field. (Think about it - the wiring is just one long continuous wire with virtually no resistance). That means for a very short time, while starting, they would draw very high loads of power.

How a motor is rated in that case, is not the maximum power it can draw, but the point where it reaches thermal equilibrium. That is, its ability to passively lose heat, is the same as the heat waste it is generating.

At only $1.25, you could try it out, but first, put some load on it for a few minutes and see if it gets hot. If it's unpleasant to the touch, it won't last long.

 

[ash ketchum]

I tried testing it with a heavier load(without a multimeter), and it DID get hot after five minutes, but not enough to burn my hand. So, shall I use it???

 

[ash ketchum]

20 Amps peak... what will it take continuous? I doubt it would be 20A

It took around 2 to 5 amps.(I added low power pedal assist in the original question as the Add-e 250w kit gave a minimum of 50w assist and this will give me 24 to 60 watts.)

 

[Hillhater]

Check the kV (rpm per volt) if its quoted, or try to measure the rpm somehow.
Usually those motors run a very high kV ..1000+ Giving (10-20,000+ rpm)
That would make it very difficult to use in a bike drive system ....even if it does last !

 

[ash ketchum]

Check the kV (rpm per volt) if its quoted, or try to measure the rpm somehow.
Usually those motors run a very high kV ..1000+ Giving (10-20,000+ rpm)
That would make it very difficult to use in a bike drive system ....even if it does last !

It's rpm is REALLY LOW. Although I can't measure the rpm, but every rpm has its characteristic "noise" of a certain pitch. According to that, the rpm is around 5000. Is that TOO much???

 

[Hillhater]

Dont guess, ..measure !
But 5000rpm on 12 volts is not too bad considering yo want a wheel speed of say 15-20 kmh which would be approx 200 rpm for a 26" bike wheel.
So you would need a 25:1 gear reduction....or 50:1 if you run 24 v to get the amps lower !

 

[ash ketchum]

Thinking of reduction, I intend to use it in a friction drive, so I might get the best out of my motor...

 

[Hillhater]

I would look for a more suitable motor. :wink:

 

[skeetab5780]

I heard from a girl friend of mine that vibrator motors are pretty strong...You can try one of those

 

[ash ketchum]

I heard from a girl friend of mine that vibrator motors are pretty strong...You can try one of those

Vibrator motors can't even move a quadcoptor propeller, an ebike is out of the question.

 

[Sunder]

I heard from a girl friend of mine that vibrator motors are pretty strong...You can try one of those

Vibrator motors can't even move a quadcoptor propeller, an ebike is out of the question.

I heard for some women, they can make the whole earth shake!

I'll get my coat...

 

[CaliClouds]

I heard from a girl friend of mine that vibrator motors are pretty strong...You can try one of those

Vibrator motors can't even move a quadcoptor propeller, an ebike is out of the question.

I heard for some women, they can make the whole earth shake!

I'll get my coat...

I can attest to this. Might be worth looking into.

 

[ash ketchum]

Another question: is the rs-775 motor REALLY 300 watts??? https://www.aliexpress.com/item/Lar...lgo_pvid=ca9531b0-422c-4541-97d9-2352d9fddaba I took a look at this motor and it is awesome!!! well, on paper. I think it is difficult to make such a motor as on its rated voltage of 12 volts it will take upto (in reality, continuously) 300/12=25 amps!!!and it is being advertised that it can take upto 24 volts without ANY problem of overheating!!! How IS this possible???( please explain it in a way that will suit me. You people usually explain like I'm a kid {well, at 13 years old I'm still a kid... :wink: } but it is better to talk a bit more directly and scientifically... :? :? :? )