Hi just to make sure!! voltages, amps and watts

Hi pretty much a newbie here, so when a rear internally geared 48 volt motor is rated at 500 watts it can be run at 1000 watts by running 22amps through it? Is that how you get a 1000 watt rear hub geared motor? Should I be checking NM rating? Wire Turns? I'm a big guy in a somewhat Hilly area.
So I am ready to buy and when I look I see Ebikeling , e Bike kit , grin tech , amazon, ebay and aliexpress. I'm leaning towards one of the first three that may be able to answer a question by email or over the phone.
Do the contollers vary a lot should I be concerned with this aspect of the system when I'm just getting started? thanks in advance.

The motor will consume as much as it needs, up to the ability of the battery and controller to provide it (actually, there's a point where it can't take any more), so the ratings are more to do with the ability to run at that power level forever without overheating.

If you're in a hilly area, a lot has to do with if they hills are short in duration, and long. That's because a geared hub doesn't shed heat very well, so where the torque helps to climb a hill, if the climb is sustained, it will burn up the motor. You can play with the simulator to see what the effect of increasing the grade, changing the voltage and controller is on the motor. Here's a 750W geared hub, using a grade of 7%, using 15A and 25A controllers for comparison. 25A provides a lot more torque, and propels the bike faster up the hill. However, it will overheat in an hour. With the 15A controller, while slower, will never overheat. So, if you have long sustained climbs, you might want the lower powered controller (or go with direct or mid drive).

If your hills are steeper than 7%, just increase the grade and hit the simulate button (both overheat). On flat ground, they both have the same speed, since voltage, not power, is determining the speed, at least in this case.

https://www.ebikes.ca/tools/simulator.html?motor=MG60_750&batt=B4816_GA&cont=C25&cont_b=C20&motor_b=MG60_750&batt_b=B4816_GA&bopen=true&axis=mph&grade=7&grade_b=7&hp_b=0&hp=0

Thanks I checked out the simulator and I think I'm starting to get the picture/ variables :thumb:

E-HP said:

Here's a 750W geared hub, using a grade of 7%, using 15A and 25A controllers for comparison.
...
https://www.ebikes.ca/tools/simulator.html?motor=MG60_750&batt=B4816_GA&cont=C25&cont_b=C20&motor_b=MG60_750&batt_b=B4816_GA&bopen=true&axis=mph&grade=7&grade_b=7&hp_b=0&hp=0

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OK, that makes sense to me. From there I rolled down the throttle on the 25A controller to 90%, which makes the load and RPM the same - 230.1 RPM, 795W - and now the 25A controller looks a lot better. Unsure whether I might be seeing some effects from the different controller implementations, I set up another similar comparison with "custom" controller values. Same result.

Basically, for a given hub RPM, the higher rated controller is able to use less amperes to drive the wheel, and thus run more efficiently -- in the output range where "Batt Amps" for the lesser controller is pegged at its nominal limit, and "Mtr Amps" is over that limit. So for a Batt Amps example, a 15A controller pegged at 15A - a 35A controller at 73% throttle will be pulling the same, and using only 14.6A. When the grade is reduced to the point where Mtr Amps is under the controller's limit, there's no difference.

Not sure I'm buying that one. Mostly not sure a half an amp difference is enough to feel, or for the motor to care about in terms of time to overheat. It may be true though, that a big controller wastes less amps into heat, than a tiny one running full out or something, causing that too small to matter difference you see on the sim.

I'm not saying these small differences don't exist, i'm saying they are small, and pretty insignificant out on the road.

In all the testing I did for Ebikekit, what REALLY matters is the load on the motor. You make that load big enough, the motor needs to be bigger, and amps higher, to make it rotate with any efficiency. To clarify what I mean by all this, a half amp difference in draw at the controller is meaningless, vs a a motor overloaded running at less than 50% efficiency. All that really matters in that situation is that you need a bigger motor, if you overload it enough.

Rule of thumb used by the warranty of EBK, is 300 pounds total weight for bike, kit, battery, luggage and rider could be warranted. It would climb 10% without overheating motors for miles, It would climb 15% for half a mile. Hell yes its running very inefficient if you are climbing 10% and the load is 300, but it would make it. At 400 pound load, 7% would kill it.

To beat it to death, what matters most with system efficiency is how much you are overloading the motor. If you want better efficiency with more weight than 300 pounds, power up till you fly up that hill at efficient rpms, and better still use smaller wheel diameter. (hub motors)

Best efficiency not overloaded is even simpler, slow to 15-20 mph, where you can put 25% of the energy needed for that speed into it by pedaling, and use 25% less battery too. Result, double the range from your setup.

All that other shit, micro differences in efficiency by changing controllers, changing windings, Its all stuff you can make up with a block or two of just pedal with the motor off. Or actually pedal hard up the hills. Yeah, its a difference, but not significant at all compared to whatever speed you ride, slow down 2 mph. Or stop overloading, get the big motor if you are that big.

dogman dan said:

Not sure I'm buying that one. Mostly not sure a half an amp difference is enough to feel, or for the motor to care about in terms of time to overheat. It may be true though, that a big controller wastes less amps into heat, than a tiny one running full out or something, causing that too small to matter difference you see on the sim.

I'm not saying these small differences don't exist, i'm saying they are small, and pretty insignificant out on the road.

Click to expand...

Small, yes. At E-HP's simulation parameters, a 20A controller was making it - never overheats - and the 25A had an hour to go before it overheated, but it's kind of a cherry-picked example - maybe it's unrealistic to simulate a 7% grade that long, 0 pedal input, etc.

I just thought it was interesting that, according to the simulator, you could turn the tables by pulling back on the throttle to where the 25A was delivering the same output - that it could do that more efficiently. So while the initial premise seemed to be that you'd be better off buying the smaller controller, apparently you'd be better off with the large one, and then switching your throttle range to one of the reduced settings that I think controllers usually tend to offer.

Interesting because it isn't clear why - is it so obvious that a controller pushing over its nominal limit is going to run a little less efficiently, that it's built into the simulation for a "custom" controller? Is there a mistake in my parameters?

In all the testing I did for Ebikekit, what REALLY matters is the load on the motor. You make that load big enough, the motor needs to be bigger, and amps higher, to make it rotate with any efficiency. To clarify what I mean by all this, a half amp difference in draw at the controller is meaningless, vs a a motor overloaded running at less than 50% efficiency. All that really matters in that situation is that you need a bigger motor, if you overload it enough.

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Well, I think that's the OP question, isn't it? What the heck does "bigger motor" mean - how can he tell the difference, when the industry is known to be pretty fast and loose with motor ratings that are pretty ambiguous anyway? "500W"?

donn said:

Small, yes. At E-HP's simulation parameters, a 20A controller was making it - never overheats - and the 25A had an hour to go before it overheated, but it's kind of a cherry-picked example - maybe it's unrealistic to simulate a 7% grade that long, 0 pedal input, etc.

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Agreed, but not cherry picked, just happenstance. Absent more information on things like what "hilly" is, the main point of the example is to illustrate that there are may concepts that are intuitive after you study the relationships, and others that are not, and are harder to explain. Apart from modeling errors, it's the non-intuitive scenarios that are most interesting to try to figure out