switch from 36v to 48v increses torque?

[Antenor]

Hello to everyone
This is my first post about technical know how...i am from Portugal and de ebikes are still an exotic thing in the roads...
Moving on, my doubt is this:
When we switch a 36v battery to a 48v battery, there is an increase in velocity, considering the same motor. But does torque increase also, or maintain the same?

Other doubt that i have is if maintaining the same battery, a geared hub motor for speed has less torque that de same motor that is for strength? Or the torque is the same, but as it is more difficult to reach the motor top speed he is weaker on the hills?
In this case, if I put a controller whit more amps ( lets say I raise from 14 to 17), the motor will be a better climber? With the same capacity of a motor geared for strength with less Amps? I am talking of 36v 250w geared hub motor, and i always pedal along with it...

thanks

 

[Drunkskunk]

Yes. If you increase the voltage from 36 to 48, you increase the speed of the bike, and the torque.
The torque is increased because increasing the voltage increases the wattage.

For example: A 36 volt, 20 amp controller lets a maximum 720 watts reach the motor. A 48 volt 20 amp controller lets a maximum 960 watts reach the motor. (Volts X Amps = Watts)

With geared hubs, the actual gear ratio stays the same between a "speed" and a "torque" motor. In reality, both the fast and slow geared hub make exactly the same torque, even when Vendors describe the slower motor as a "torque" motor. The difference isn't the gearing, it's the wind count on the motor. The more times you wrap a copper wire around the stator of a motor, the slower it will go. Fewer turns of copper wire will make the motor faster. But if the same amount of copper is used, then the torque produced will be the same.
The reason the slower motor is called a "torque" motor is because the slower motor won't over heat as fast. While it pulls just as hard as the fast motor, it can pull longer without overheating, like when climbing a hill. The fast motor can pull just as hard, but may over heat trying to climb the same hill.

you can try out this motor simulator to see how this works for your self, here: http://www.ebikes.ca/tools/simulator.html

 

[dogman dan]

Yep,, in general,, increase watts and you increase torque. This can be done by increasing voltage, or by using a new controller that runs at higher amps.

But the best results are by doing both 8) . If the motor can stand that much more watts.

36v to 48v,, gets you 25% more watts, or is it 33%. in any case, in the example above, about 250w more by adding 12v more.

 

[Antenor]

Thanks to both by the explanation

So if I am satisfy with the torque of the motor, but not with the speed, I can bui the speed version of the motor.

My personal case is that i already had a 250w 36v 17A geared hub motor, but the speed was only 15.5 mi/h. I liked the torque, was enough for me because I always pedal along. I change for a bafang bbs02 500w 36v but, for me, even with changes to the controller, was to artificial. I dint like to be pulled by the motor...so I sold it.

Now I am considering buying again a geared hub motor, with 250w (i now that in reality is more), but i would like more speed. The seller told me that is not a good idea to buy the speed version to do offroad, that was best to buy the torque version and use a controller and battery of 48V...the only problem is that that setup will cost much more that buying the speed version with a 36v battery.

Probably, for having less overheating issues is better to use the speed version with only 14Amps? There is a option for 17Amps...

I now that this are really basic doubts, but is not easy to get it right at the first or second...but I am sure that with the help of other experienced users this time I will have more chances to get it right

 

[chas58]

Bom Dia! Todo bem?

Good questions, and drunkskunk and dogman have good answers.

There is a lot to balance here.

It depends a bit on the motor, but generally if you are not going full power under 10mph, you won’t have overheating issues. That is a gross generalization, for the specific numbers, you can calculate the overheat point here (if you know the motor): http://www.ebikes.ca/tools/simulator.html

Theoretically if you keep the power the same you can go up to 48v and reduce the amps by 30% and not have any additional overheating. The problem is that if you don’t get the motor up to a high speed, you may be pulling maximum current all the time and have problems with the controller overheating.

Portugal can be kind of hilly. Do you have hills where you ride? If so, mid drive might be best.

What speed are you thinking of? 15.5mph indicates a 200rpm motor at 36 volts. Typically you can run those at 48volts (again, not at full power and low speed) at get 20mph. Alternatively you could get a 260rpm version and run it at 36volts and get the same speed (but with 33% less power and less risk of overheating the motor.

Ask the vendor the no load RPM of the speed vs the torque version. Again, these motors will have the same torque, but the lower speed motor will be able to run full throttle at lower speeds (hill climbing) longer before overheating.

 

[Antenor]

Obrigado chas58

My zone is a quite hilly, principally the area where I go to off-road.
I already had a mid drive bafang BBS02, but I didn't like the way it drags me to the trails... even with the controller mods I never felt connected to the drive
Maybe the TSDZ2 with torque sensor will be better, but I don't have a seller or assistance to that motor close to me, and I am afraid that if it has issues it will be hard to solve.
The kit is this one http://www.ciclotekstore.com/b2c/producto/9822150/1/kit-platinium-lcd5-b-o-s-sin-bateria, and it has a 155 mile/h version and a 20.5 mi/h version

Resuming my options:
1-geared hub motor 250w 36v 15Amp controller, version speed
2-geared hub motor 250w 36v 17Amp controller, version speed
3- geared hub motor 250w 48v 18Amp controllers, version torque

From the options above, which one is less affected by overheating through the hills, in off road conditions... I always pedal with the motor and use the bike gears to help the motor

 

[dogman dan]

BBs02,, but have ability to turn off the PAS,, and use pure throttle for motor control would be the best solution.

PAS all the rage, and the law some places. But nothing can compare to a really fast computer controlling the motor, your brain, and a throttle. Infinitely adjustable, and instant. Takes practice to get it really sweet, but nothing pas can compare to your brain reacting to the feel of your pedals. yeah,, torque sensors are great and all, but you can change your power setting faster with good throttle use.

 

[Antenor]

When I had de Bafang mid drive I used the pas...maybe thats i i didnt like him

What kind of trotle you use? Twist, half twist or other?

 

[chas58]

Obrigado chas58

My zone is a quite hilly, principally the area where I go to off-road.
I already had a mid drive bafang BBS02, but I didn't like the way it drags me to the trails... even with the controller mods I never felt connected to the drive
Maybe the TSDZ2 with torque sensor will be better, but I don't have a seller or assistance to that motor close to me, and I am afraid that if it has issues it will be hard to solve.
The kit is this one http://www.ciclotekstore.com/b2c/producto/9822150/1/kit-platinium-lcd5-b-o-s-sin-bateria, and it has a 155 mile/h version and a 20.5 mi/h version

Resuming my options:
1-geared hub motor 250w 36v 15Amp controller, version speed
2-geared hub motor 250w 36v 17Amp controller, version speed
3- geared hub motor 250w 48v 18Amp controllers, version torque

From the options above, which one is less affected by overheating through the hills, in off road conditions... I always pedal with the motor and use the bike gears to help the motor

So, the lowest power and lowest speed will overheat the least.

How fast and how long do you climb the hills?
Just a rough guess, but if you are going more than half the motor's top speed when climbing a hill, you shouldn't have a problem. If you are doing 25% of the motor's top speed climbing a hill, you have maybe 5 minutes until it overheats? If you use more current (17 vs 15 amps) or more voltage, it will overheat faster.

Those speeds are in mph not mph. Running the slow speed motor at 36v and 15amps probably will never have problems climbing. But then again, above 15.5 kph, it is not going to be helping you much at all. Its just a climbing motor.

Personally, I would probably get the mid speed motor (25kph) at 36v and 15 amps for hill climbing since you will be pedaling too (assuming you are not racing a funicular up one of those hills in Lisbon!). Again, it won't be helping you much at all above that speed - you'll be on your own for going faster. Electric motors have a very sharp drop off in power once they reach their top speed.

 

[chas58]

BBs02,, but have ability to turn off the PAS,, and use pure throttle for motor control would be the best solution.

PAS all the rage, and the law some places. But nothing can compare to a really fast computer controlling the motor, your brain, and a throttle. Infinitely adjustable, and instant. Takes practice to get it really sweet, but nothing pas can compare to your brain reacting to the feel of your pedals. yeah,, torque sensors are great and all, but you can change your power setting faster with good throttle use.

don't like even torque sensors much, eh?
I'm on the fence about getting one. But holding the throttle down for an hour for my commute gets kind of old. Agreed though, I do like to quickly and intuitively adjust the throttle for my speed and need for power.

 

[Antenor]

Maybe if I tried a torque sensor I would like...but because I don't have that possibility is better do go with I already tried...and I like more the gear hub low power assiste.

For the options above , what's the one who stress less the motor in off road ?

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[Antenor]

The slowest version is to slow for my taste...between the 36v 17amp speed version and the 48v 18amp with the slowest version the speed will be more or less the same but who would be the one that overheat less?

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