750 watt vs 500 watt motor

[indianajo]

Hello, I don't know if this is helpful or more confusing, but here goes. I have two eBikes. Both have Bosch motors mid drives,
a 400 and a 500 watt battery and Identical controllers. I flip flop the batteries all the time and feel no difference in response based
on the battery.
.

You need to learn the difference between watts and watt-hours. See post #9. Watt-hours is range. Watts is torque times lever arm times rotations, or equivalently, force times distance.

 

[MechaNut]

The RAD has a DD hub motor. When I am pulling the trailer with my 90 year old mother in it, I will not be going far. I would guess 20 miles. Without the trailer, I will be riding 50 miles, most of the time in PAS 1. (But I just rode a century ride two days ago and want to do more of them. I needed 11 bars, so 2 batteries were not enough.)

I think you're getting overwhelmed by the numbers. Here are some good points of reference to understand what all the numbers mean.

Motor Watts: How many watts of power it will contribute on its own to generate propulsion at peak demand (full throttle or maximum pedal assist). This is more important for figuring out how good a motor is at going fast.

Motor Torque: How much work, measured in newton meters (nm) of force, that the motor will provide. This is really the most important number to look at to see how good the motor is at pushing or pulling things around.

Battery: How much electricity it holds, how much power it will provide to the motor, and basically how big the "gas tank" is.

There are two main types of hub motors:

Direct drive motors have two main advantages. Direct drive motors have no moving parts inside, so they are much more durable and quiet. Direct drive motors can also do regenerative braking, so can put some electricity back in the battery under braking. The downsides of direct drive motors are they are typically heavier than a geared motor, provide less torque than geared motor, and often have a higher degree of drag when not powered (because of regen braking).

Geared motors are typically smaller and lighter. Geared motors are typically better at providing torque. Geared motors have moving parts and are typically noisier and over time can wear out a little easier. Geared motors can't do regen braking.

The two bikes models in Rad Power Bikes lineup that use direct drive are the Rad City and Rad Wagon. All the rest use geared motors.

The best number to look at to figure out how much electricity the battery will hold is the watt hours rating. If a watt hours number isn't published the quick way to figure it out is Volts X Amp Hours = Watt Hours. Basically, this is how big the "gas tank" is. In the case of a 2019 Rad Power Bike it is 48 volts X 14 Amp Hours = 672 watt hours. This will also let you figure out how much it will cost to charge the battery since public utilities usually charge by the kilowatt hour (1000 watt hours = 1 kilowatt hour).

My 2018 Rad City has had no difficulty pushing me around (I'm north of 300 lbs) with the exception of long and steep hill climbs. The motor won't get me over the hill on its own, I have to help.
My Rad City is a US spec 750 watt. At PAS levels 1-3 the watts provided by the motor are under or around 500 watts. I don't see over 500 watts until I go into PAS 4 or 5 or use the throttle.

Obviously if you really want to dig in deeper and get into some really deep levels of understanding you can and this is a great forum to do so, but if you want a "just the basics" understanding I think this is a decent level to start at.

 

[DragNLady]

As pointed out earlier, it doesn't matter what motor you have it depends on the battery and controller! Battery voltage times controller amps V x A = W. For example, my stock Radrover put out 500 watts. I changed my controller to 35A and with the 48 volt battery I'm running three times the wattage ( 35X48=1680 but my controller is limited to 1500 watts. That makes riding safer and more fun. I've done similar things to some of my other low powered bikes.

If it doesn't matter if I have a 500w or a 750w motor, then why are the 2 options available??? You can't tell me there is no difference between the two. I am TRYING to find out what the advantage a 750 will give me over 500.

 

[DragNLady]

I wasn't aware that RAD offer their City in reduced speed configuration for Canada. Could be due to some Canadian red tape, and then you don't have a choice. Motors are likely the same, the speed is limited by controller. But, if you do have a choice btw 750W DD City and 500W DD City, there is no sense getting 500W DD version, especially with heavy trailer in mind.

As noted by others, watt-hours are a measure of battery capacity and have little to do with motor. Motor power is in watts. More watts - more pull, or more speed. More watt-hours in battery - longer range.

So which one are you talking about - 500W motor or 500WH battery?

I don't know what I am talking about. LOL!!! I am referring to the U.S. 750w and the Canadian 500w. I "assumed" the 750 and 500 numbers were for the motor, but maybe I am wrong?

 

[DragNLady]

Wait, where did you get the idea that 750W is going to cost you more than 500W?

Rad City Step Thru 500W $1,999 Canadian ($1498.81 @ today's rate)
https://radpowerbikes.ca/products/radcity-step-thru

Rad City Step Thru 750W $1,499
https://www.radpowerbikes.com/products/radcity-step-thru

So the 750W will cost you whopping 19 cents more than the 500W version.

No, not true. I will have to pay $500. duty on the US bike if I import it to Canada. And before people start telling me I can't take a 750 bike to Canada, yes I can. I called the RCMP and asked them what would happen if they caught me riding a 750 watt bike in B.C. He said nothing, UNESS I run into someone and injure them.

 

[MechaNut]

I don't know what I am talking about. LOL!!! I am referring to the U.S. 750w and the Canadian 500w. I "assumed" the 750 and 500 numbers were for the motor, but maybe I am wrong?

The difference between the US version and the Canadian version is the programming in the motor controller. The controller is the brains of the bike if you will. If you look at the bike the controller is housed inside the black plastic box between the rear wheel and the seat tube. Canada has different e-bike rules than the US does in regards to maximum power output and Rad Power Bikes complies with Canadian e-bike law by restricting the output to the motor via software settings on the controller. The hardware is the same (motor, battery, etc) between the two models, just the programming on the controller is different.

edit: I'd be surprised if there wasn't a set of instructions out there somewhere on how to reconfigure the Canadian "version" of the bike to operate at 750 watts maximum output vs. 500 watts maximum output.

 

[DragNLady]

Sorry to say, I am still 100% confused. Many of you have taken a great deal of time to try and educate me, (which I greatly appreciate!) but several of you have said there is NO difference between the U.S. 750 w and the Canadian 500w. (My brain simply cannot understand that logic. If there is no difference, why are the 2 made, why are they all not made with 500w? My brain says there HAS to be a difference!). . . . . . . . Someone else says: " if you do have a choice btw 750W DD City and 500W DD City, there is no sense getting 500W DD version, especially with heavy trailer in mind." . . . . . . . I need someone to explain WHAT the difference would be between these two bikes. Would the 750w be more beneficial if I am going to be pulling a trailer with 200 pounds? That is all I am trying to figure out. Thank you for your patience.

 

[DragNLady]

The difference between the US version and the Canadian version is the programming in the motor controller. The controller is the brains of the bike if you will. If you look at the bike the controller is housed inside the black plastic box between the rear wheel and the seat tube. Canada has different e-bike rules than the US does in regards to maximum power output and Rad Power Bikes complies with Canadian e-bike law by restricting the output to the motor via software settings on the controller. The hardware is the same (motor, battery, etc) between the two models, just the programming on the controller is different.

Okay, thank you MechaNut, that is very helpful! I understand now that both bikes are built exactly the same, but because of the controller, they PERFORM differently. In my mind, if one outperforms the other, they are not the same bike! So how does the 750w outperform the 500w???

 

[harryS]

Pulling Mom on a Rad City direct drive motor? In my opinion, if there is a 750W option and it buys a motor with bigger magnets, that's the better solution for towing, and add a bigger battery. If it's the same motor, but they just rewrote the spec's, I wouldn't pay any more than the 19 cents Timpo listed as the difference,

I think a DD will need a good battery to pull 200 pounds. What would be cool is a motorized pusher trailer. Have your mechanic weld one one up for you. Just dreaming.

 

[AHicks]

Okay, thank you MechaNut, that is very helpful! I understand now that both bikes are exactly the same, except they are programmed differently. So even though both bikes are the same, they do NOT perform the same. So how does the 750w outperform the 500w???

Much like comparing a car being driven at 2/3 throttle vs. a car driven wide open. Same exact vehicle, one producing 2/3 the power of the other.

The 500w motor is a 750w that is being starved for power electronically.

Regarding the Rad City, as one might suspect, for those serious about getting full power (750w) from their 500w motor, it's not that difficult for somebody that knows what they are doing.

 

[DragNLady]

Pulling Mom on a Rad City direct drive motor? In my opinion, if there is a 750W option and it buys a motor with bigger magnets, that's the better solution for towing, and add a bigger battery. If it's the same motor, but they just rewrote the spec's, I wouldn't pay any more than the 19 cents Timpo listed as the difference,

I think a DD will need a good battery to pull 200 pounds. What would be cool is a motorized pusher trailer. Have your mechanic weld one one up for you. Just dreaming.

First of all, Timpo is wrong in saying there is a 19 cent difference in price. I will have to pay $500. in duty to import the bike to Canda, so the U.S. Rad will end up costing me $500. more.

 

[MechaNut]

Okay, thank you MechaNut, that is very helpful! I understand now that both bikes are exactly the same, except they are programmed differently. So even though both bikes are the same, they do NOT perform the same. So how does the 750w outperform the 500w???

The "brain" of the US "version" allows the motor to use a maximum of 750 watts of electricity to reach its top speed of 20mph and the "brain" of the Canadian "version" allows the motor to use a maximum of 500 watts of electricity to reach its top speed of 20 mph. If both configurations have the same torque rating they will both push/pull the same, but 750 watt configuration will get to its top speed faster because it can use more electricity.

 

[Alex M]

I'd be surprised if there wasn't a set of instructions out there somewhere on how to reconfigure the Canadian "version" of the bike to operate at 750 watts maximum output vs. 500 watts maximum output.

Needs minor re-programming of controller. Which RAD doesn't want us to do. One easy alternative is to replace OEM display with KT LCD3 programming display. Looks nicer than RAD display, too - more compact and sits lower/closer to handlebars.

 

[Alex M]

I need someone to explain WHAT the difference would be between these two bikes. Would the 750w be more beneficial if I am going to be pulling a trailer with 200 pounds?

This is what happens when there is too much info - difficult to find what you need.

Several people answered this already - 750W version will provide more pull and/or more speed. (Assuming they really limited the power of motor for Canada, and not just re-wrote the specs).

Though I think that even "unrestricted" 750W DD motor is not the best choice for cargo application.

 

[Alex M]

I saw KT LCD3 tutorial. Not any more difficult than setting up OEM display after you've bought the bike, - just more screens to go through.

Luna programming cable has one round plug for BSD, and one USB plug for PC or laptop. You can't plug it in KT LCD3. But this is an interesting thought - why there is no software - similar to that BSD programming app - that you could download to PC and program any controller without buying KT LCD3. Or will that BSD app work for other controllers?

 

[Deleted member 4210]

If it doesn't matter if I have a 500w or a 750w motor, then why are the 2 options available??? You can't tell me there is no difference between the two. I a TRYING to find out what the advantage a 750 will give me over 500.

The Rad City Canada version has the same torque rating 40 Newton meters as the US version. So in your situation in terms of pulling power ,the 750 watt motor offers no advantage. The motor is the same one, albeit with a different external nominal nameplate rating. The controllers might be a little different with the amperage (current) allowed to the motor from the battery being a little higher on the 750 watt motor.

Your bigger issue is 40 nm rated motor is fairly weak, and might not feel satisfactory when you are towing up a hill.

If you are curious in learning more about motor nameplate ratings and why any vendor would rate the same motor differently, pm me, and I can elaborate.

 

[Deleted member 4210]

The difference between the US version and the Canadian version is the programming in the motor controller. The controller is the brains of the bike if you will. If you look at the bike the controller is housed inside the black plastic box between the rear wheel and the seat tube. Canada has different e-bike rules than the US does in regards to maximum power output and Rad Power Bikes complies with Canadian e-bike law by restricting the output to the motor via software settings on the controller. The hardware is the same (motor, battery, etc) between the two models, just the programming on the controller is different.

edit: I'd be surprised if there wasn't a set of instructions out there somewhere on how to reconfigure the Canadian "version" of the bike to operate at 750 watts maximum output vs. 500 watts maximum output.

This is only true if they are supplying the same amp rated controller on both, and are limiting amp draw via programming on the 500 watt version.

 

[Alex M]

This is only true if they are supplying the same amp rated controller on both, and are limiting amp draw via programming on the 500 watt version.

Yes. We don't know what RAD did to Canadian version. Either a weaker controller, or restricted amps on the same controller as 750W.

Net result is the same - lower amps mean lower speed. Also, limited hill-climbing ability, because you start slower, 40nm torque is pretty low, at some point it will stop. Though the latter is not too important for the OP, she is on flat terrain.

 

[DragNLady]

The "brain" of the US "version" allows the motor to use a maximum of 750 watts of electricity to reach its top speed of 20mph and the "brain" of the Canadian "version" allows the motor to use a maximum of 500 watts of electricity to reach its top speed of 20 mph. If both configurations have the same torque rating they will both push/pull the same, but 750 watt configuration will get to its top speed faster because it can use more electricity.

Thank you MechaNut, you are awesome, I finally got my answer! So, if I understand correctly, the ONLY difference in having a 750w rather than a 500w, is that the 750w will get me to top speed faster. That is NOT worth spending an extra $500. for. THANK YOU VERY MUCH for explaining it so I can understand!

 

[DragNLady]

The Rad City Canada version has the same torque rating 40 Newton meters as the US version. So in your situation in terms of pulling power ,the 750 watt motor offers no advantage. The motor is the same one, albeit with a different external nominal nameplate rating. The controllers might be a little different with the amperage (current) allowed to the motor from the battery being a little higher on the 750 watt motor.

Your bigger issue is 40 nm rated motor is fairly weak, and might not feel satisfactory when you are towing up a hill.

If you are curious in learning more about motor nameplate ratings and why any vendor would rate the same motor differently, pm me, and I can elaborate.

Thank for your help, but as I previously said, I will only be riding on flat terrain, NO hills at all.