How far can you upgrade a 300w motor?

wheelbender6

wheelbender6

Well-Known Member
There are a lot of inexpensive ebikes and ebike kits that are 24 volt and 250 to 350 watts. You can’t increase the wattage of the motor, but you can upgrade the controller and batteries.

Would I be able to use a 36v 20AH controller with 20 AH batteries on a motor rated at 300 watts or so (brushless controller & motor)?

How could I calculate the max volts and AH I could use on an e-motor if I know the wattage? Is there a reference table where I could look it up?
 
This got tossed around a little bit in the currie motor thread. Given motors are manufactured differently, it's anyone's guess exactly how much you can over-volt a motor. I've gotten the gist that you can boost the 24V currie brushed motors by 12 volts. The wattage will go up by about 50%.
 
I have run a currie 24 at 48v for a short distance then it was the controller that fried not the motor. I also over powered a brushless hubber bubber and it still is junk
lol.
 
wheelbender6 said:
There are a lot of inexpensive ebikes and ebike kits that are 24 volt and 250 to 350 watts. You can’t increase the wattage of the motor, but you can upgrade the controller and batteries.

Would I be able to use a 36v 20AH controller with 20 AH batteries on a motor rated at 300 watts or so (brushless controller & motor)?

How could I calculate the max volts and AH I could use on an e-motor if I know the wattage? Is there a reference table where I could look it up?
Click to expand...
As a general rule, if you have a 24v or 36v motor, you can usually upgrade the controller and batteries to 50% 24 up to 36 and 36 up to 48..
Wattage on a motor is what it's rated at continuous..
Let's use a 24v motor at 250w..
Motors are usually rated for 85% efficiency.. So you would need to supply 300w to get the 250w. (350x.85)
24v into 300w is approx 12a.
So at 24v the motor is rated for 12a/300w continuous..

You want to run that same motor on 36v...
Well 36v into 300w is approx 8a.
So at 36v the 24v motor should be able to be run at 8a continuous without problems.

Hope that helps.
(and yes, it's better to upgrade the controller, most controllers won't handle too much past their ratings, while motors can as long as you don't ride them too hard)
 
Yeah, what he said :D.....and be prepared to find space for that new 36 volt controller. I found out that they can be as much as 3 times as big as a 24 volt controller. Not much space on a bike to mount a box that big and keep it on the inconspicuous side. I managed to strap one on under my rear rack. The upgrade was well worth the effort. dance1
 
Thanks for the advice. The replies I got on a dedicated E site were about 50-50 on overvolting the motor.
Some said that many 500w motors are advertised as 300w, due to local regulations or to help parents feel that it is a safe way to get around.
The other half of the responses were from riders that had experienced an overheated (melted) motor component, controller or wiring from overvolting the motor.
It seems that if you get a smoking deal on a 24v bike, especially one purpose built to carry a battery pack in the frame, it might be better just to buy and install an entirely new motor kit for it with the volts/watts/amphours that you wanted from the beginning.
 
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My best advice is for the currie I know. run them at any voltage you want they aren't that expensive used.... For the controllers go with the right size battery you want to run. Everything else is the same for either voltage.
 
wheelbender6 said:
Thanks for the advice. The replies I got on a dedicated E site were about 50-50 on overvolting the motor.
Some said that many 500w motors are advertised as 300w, due to local regulations or to help parents feel that it is a safe way to get around.
The other half of the responses were from riders that had experienced an overheated (melted) motor component, controller or wiring from overvolting the motor.
It seems that if you get a smoking deal on a 24v bike, especially one purpose built to carry a battery pack in the frame, it might be better just to buy and install an entirely new motor kit for it with the volts/watts/amphours that you wanted from the beginning.
Click to expand...

Also, take what you read with a grain of salt. Having been checking out some vids of ebikes and their "builders" on Youtube, I'd not listen to anyone under 50. rotfl Me thinks quite a few push the limits of these kits to the extremes, then call it junk when it finally goes Chernobyl on them. YT is full of stupid and don't doubt we have a bunch involved with our hobby....even on "dedicated" forums. The same for any hobby, not just our's. Of course, I'm not referring to all of them as stupid. There are the few who truly know what they're doing.

So far, I've found suggestions and advice from the few here to be sound as I've tried them myself. No mega volts through a mini motor and China Syndromes suffered. Just practical application, most of which push at the minimum, never the max and make this hobby more or less affordable for just about anyone. Once you get a rig and some experience, then it's time to start looking at bumping things up a notch. Now you can consider new tech power sources, special motors, etc. for more speed and range. The challenge and fun is to achieve such issues as cheaply as possible.

Just my couple of coconuts and wanted to pass on that little caveat. Good you're doing your research. I was reading whatever I could find, online, for almost a year before settling on this forum and finally buying my first rig. .elec. I also procrastinate a lot. I think they're sometimes called "senior moments". zpt
 
I try to report my experiences not theory because I'm not that smart. Before I say something I have usually tested it in the real world, not a lab somewhere. I would never buy a 250 watt motor hoping to get five hundred out of it. I think I would buy a 500 and hope to get 750 watts from it. To my way of thinking the more motor you begin with, the better your chances of having it perform the way you want.

All the motors I run now are rated 600 watts at 24v... I run them at 36v but almost never get them wide open throttle. I do it for the hills we have here. Still they will hall butt if I need them to.

The real world experiments are also reported when they fail, because it is just as important to know what doesn't work. I have burned up controllers because they won't handle the over voltage. I have never and would never suggest over volt a controller. However I have two that are rated 24volts that run 36 routinely just fine.

I am hoping that will be advantageous with the Nimh batteries as the low voltage knock off will be lower. It might not make any difference at all. It would be nice, if I could get a little push out of the batteries a little longer. I do have to be careful with the sla not to run them down too low. Since in theory I could. Practically the motor performs so poorly with a battery pack that is only a little down, that it gets recharged long before the cut off point.
 
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