Differences between different 1000w 48v hub motors

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jsmith   1 µW

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Differences between different 1000w 48v hub motors

Post by jsmith » Sep 26 2017 4:55pm

Hi everyone,
I'm a newcomer about to build my first ebike.
I can see that there are many different Chinese suppliers offering 1000w 48w motors at similar prices.
They all advertise different top speeds ranging from 45kmh to 55kmh.
My question is do they all really have the same top speed and the different suppliers are just tying to differentiate their products or could it be that two 48v 1000w hub motors have different top speeds with the same 21a controller.
Thanks in advance.

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dogman dan   100 GW

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Re: Differences between different 1000w 48v hub motors

Post by dogman dan » Sep 27 2017 6:18am

Well, first of all, you have the degree to which vendors fudge the specs. Motor rpm is specified as a certain rpm at a certain voltage, with no load. That is, wheel in the air, spinning without a load on the wheel like a rider. One vendor may be giving you no load rpm converted to mph, while another might be giving you real world speed with a typical weight rider on the bike, on flat ground. Second,, there are differences in motors.

The number of turns in the winding can cause two almost identical motors to have different no load rpm at a specified voltage. The best way to compare motor speeds is to get the actual no load rpm specification, for either 36v, or 48v, and compare apples to apples.

The most typical you see are 7 turn, and 6 turn. 7 turn will hit around 26 mph ( loaded, meaning a 200 pound rider on a typical bike) on " 48v" defined as "charges to 54.6v. The 6 turn will be about 3-4 mph faster, and be able to hit about 30 mph.

But that's not the end of differences. Some "48v" batteries are stronger than others, or charge to 58v. So you can have one that sags 6v when you hit the throttle, and others that sag only 2v. So in use, you might have one that gives you 50v when running, and another giving you 56v. The lower the actual working voltage, the slower the max motor rpm (no load) will be.

All this pertains to 26 inch wheel, or 700c. The same rpm motor will hit a lower top speed in 20" wheel, but perform better. So with the small wheel, you might have a lower no load speed, yet still have pretty decent performance with the load.

You asked about amps,, if both have at least 20 amps, then there is enough amps to potentially hit 30 mph, which typically takes around 1000w. if there is not enough amps, like only 750, then a more likely top speed is only 25 mph.

Confused enough yet,, I could make it worse easy.

Philaphlous   1 kW

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Re: Differences between different 1000w 48v hub motors

Post by Philaphlous » Sep 27 2017 6:38pm

I got the absolute cheapest 1000w hub motor possible on ebay and I can end up doing 35mph with my 48v battery on a full charge...I guess it just depends what you get. The spokes and wheel tho were crap...they are tighter but they still creak when I ride... It came with a 26A 12fet controller also..with no regen

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dogman dan   100 GW

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Re: Differences between different 1000w 48v hub motors

Post by dogman dan » Sep 28 2017 7:46am

It also depends on the calibration of your speedo.

But 35 mph, no wind, maybe even slightly downhill but not enough to see it, is plausible when your battery is full, and 58v with low sag, and if your controller is a 30 amps controller.

58v x 30 amps is 1500 amps after all, with sag very likely you still have substantially more than 1000w. . That is mathematically able to get you 35 mph for sure.

Fairly obvious that your motor is the 6t, which is common with the "1000w" kits. 7 t more the norm with a 36v kit. With a 22 amps controller, and sag to 52v under load, you'd still have a solid 1000w, and hit 30 easily, with a 6t motor.

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Ykick   100 GW

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Re: Differences between different 1000w 48v hub motors

Post by Ykick » Sep 28 2017 9:52am

dogman dan wrote:It also depends on the calibration of your speedo.

But 35 mph, no wind, maybe even slightly downhill but not enough to see it, is plausible when your battery is full, and 58v with low sag, and if your controller is a 30 amps controller.

58v x 30 amps is 1500 amps after all, with sag very likely you still have substantially more than 1000w. . That is mathematically able to get you 35 mph for sure.

Fairly obvious that your motor is the 6t, which is common with the "1000w" kits. 7 t more the norm with a 36v kit. With a 22 amps controller, and sag to 52v under load, you'd still have a solid 1000w, and hit 30 easily, with a 6t motor.
Most of us know you know better - that looks like a typo....
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