Can I use my 45a controller on a 1000W rear wheel?

Hello, I now have my 2nd build ready to get built and I have a few questions.

I plan to swap the battery between the 2 bikes, my 1st bike set up is (to fast) 52v20ah bat with 1500w rear wheel with 45amp controller. I honestly cannont believe how fast this bicycle is, I have well over 100K miles on street bikes and dirt bikes, I've done 150mph on the streets and now I have done 45mph on a bicycle and its more insane on the damn ebike. I have logged over 500miles in June on my ebike, just a great time!!

Now I am building a Fatire and I got a 1000w rear wheel and will use my 52v battery, the 1000w rear comes with a smaller controller, can I use the 45amp controller that came with my 1500w rear wheel or should I just use the 20 or 25amp it comes with for the 1000w rear wheel.

Thanks for all the help!

If you use the same controller, then unless you change it's settings (if it has a way to do that) it'll put the same power thru the new motor it did thru the old.

If the new motor has the same winding/design etc as the old one (even if it's a different brand/etc, it could), it'll probably run at the same speed.

So what you could do is use the old motor/etc but just install a new controller that has a speed limiter function.

If the new controller you're getting doesn't have a speed limiter function, and the motor it's on is wound/designed the same as the other, it'll probably go the same wheel speed (unloaded) as the first bike. Because of wind resistance, and power needed to go a certain speed, it could end up slower than the first one, but probably not because of the motor itself.

Or just use the throttle judiciously, so it doesn't go too fast.

If for whatever reason you simply can't make yourself use less throttle, and the controller doesn't have a way to do it in settings, you can limit the throttle's max output electrically with some resistors; there's a number of threads discussing how to do that if you need to.

Are they even the same? Brush/brushless? Hall sensors both/neither? A bit short on info?

If your 1500w wheel is thicker at the motor, and heavier, it can handle more watts than your 1000w.

I would bet that your 1000w wheel is not a 1000w motor. very likely, its a 500w rated motor. 28 mm wide magnets, motor weight about 15 pounds more or less, often called the 9 continent type. If it weighs more, then it most likely has plenty of copper and magnet to handle your controller fine, unless overloaded. Like trailer towing, or extreme long steep hills.

if it is the 500w, that motor can handle 3000w for short times, like under 30 min ride at 40 mph. For that motor, it would require 72v to reach 40 mph, and 40 amps. (3000w)

At 48v, it will likely get 30 mph, and perhaps more at 45 amps. That is more like 2500w max, and can take it longer. But to ride very long rides the max watts for that 500w rated motor should be around 2000w. 48v x 40 amps. So for longer rides, avoid full thottle till you are at 30 mph or so, keeping the watts down as you accelerate. That should work fine on the fattie.

Dauntless said:

Are they even the same? Brush/brushless? Hall sensors both/neither? A bit short on info?

Click to expand...

brushless, hall on both.
I thought that was a given in 2018.

thanks for all the replies everyone,

I just want to know if I can use my 45amp controller on a 1000w wheel? will a higher amp controller make the bike faster?

Already answered that as much as we are able to with the available information.


If you go to http://ebikes.ca/simulator, and find your motor / controller /battery (or enter in the numbers for the stuff you can that's not listed, if you know what they are), you can simulate your bikes with different stuff to see what speeds/etc you might get.

If you don't know the parameters and your stuff isn't listed, you can use generic stuff to make a basic guesstimate of how it might behave, but your actual results could be fairly different.