agniusm wrote:I think i will leave reduction of 5:1 as per my calculation it gets me to 33kph and ups the power usage to 300W which is 24W more than motor capable and 50W more than controller is capable. Max rating on the motor is 11.5A which at 24volts is 276W. As i mentioned before, one controller is rated at 200W and the other at 250W. So there you go, perhaps this motor is capable of delivering 350W as visual appearance is identical of that 250W and that 200W.
Just becauise they look the same doesn't mean they *are* the same. But it's pretty likely they're similar enough as to not matter--however, what that says to me is that it is just as likely they took a 200W motor and stuck a 250W label on it.
Meaning you'd be running it at nearly twice the power it is actually meant for, if running it at 350W. Maybe it'll do it, maybe it won't. You'll have to try it to find out.
I figured out a way to make cooling with airflow through the brushes without making it exposed to rain or splash.
If you can cool the brushes and comm, and the windings, it can definitely take at least a little higher power. How much? Dunno...gotta test that.
I don't know how you state that power W and current A are not used together as they are related to each other as my two nuts and a stick P=I*V?
In that equation, yes, but not necessarily in ratings for things. For example, you might have a motor that is rated at 1000W, but also rated at only 20A. It is also rated at 48V, but that is only so that it stays within a certain RPM range at maximum--the voltage rating can often be exceeded by however much you like, even several times higher...but not necessarily so on the W or A limits. Theoretically, you would not want to exceed 20A even if you ran it at a much lower voltage to keep it below the 1000W limit, too, because the higher continuous current could damage the wires (or brushes or commutator in a brushed motor). Whether it actually would, I don't know. Depends on how long you run it above the rating--continous operation above the rating is where failure is expected--bursts above that might be ok--depneds on the device.
Mostly the W limit has to do with how fast you can remove the excess heat from the motor. If you can keep it cool all thru the whole motor, you can just about put whatever power you want thru it until you twist the laminations off the shaft or twist the shaft itself.
The A limit is another thing: it has to do not just with the current the wires (supply and windings, as well as wires to the brushes, and the brushes and comm segments themselves) can take, but also with saturation of the motor's iron (steel). If you put enough current into it to cause saturation, then most of (or all of) the current above that does is cause lots of heat; it's no longer doing any extra useful work. Whether the rating they give on those motors has anything to do with the saturation limit, I don't know--it might just be the continous current the brushes/comm can take without damage, or even what the supply wires will take without heating so much they melt insulation. Again, if you could keep it cool enough you could still put whatever extra current you want thru it, but that current won't be doing extra work at that point.
These ratings on quality motors are usually set at a point they could run all day, every day, forever, without failing because of the current or power.
But on these little Unite-type motors, it is more likely they are rating them for what they think they can get away with, and I am not sure you could really even run them at their ratings "forever", without a failure directly related to the amount of power or current being put thru them. It even varies from motor to motor, as I have seen a fair bit of quality variation between different units, in teh ones I've had and the ones I've seen posted about here on ES and elsewhere. Some are pretty nice, and some are just disasters waiting to happen.
I've seen all sorts of ratings on ebike motors, and some of them are actually reasonable--for instance, the 9C 28xx series is a "500W" motor, but it is easily possible to run it "forever" at twice that without modifications, without failure. Might even go 3x that. There have been other motors, like my little Fusin 350W geared hub, that can take 500W for a little while but not forever, and eventaully will get so hot that the halls can stop working if run above that for any serious amount. Peakks at 1200W are ok but they heat it up quick, and 700W is pretty unhealthy for it--would probably destroy something if I kept going more than a few minutes. Some of the "1000W" unite motors have been run above that ok, and some don't even run at that wattage "forever". (I suspect part of the difference is the current they're run at).
Basically, device ratings are just individual limits, not part of an equation. If you have a FET that can do 150W power dissipation, and is also rated at 75A current, and is also rated at 150V, you cannot combine all those numbers to equal anything using the power equation. They are separate limits, meaning you should not exceed any individual limit. Don't go over 150W total, *and* don't go over 75A, *and* don't go higher than 150V. Exceeding any of the ratings could (probably would, maybe not instantly) damage or destroy the device.