24V motor

[dimitrib90]

Does anyone know what the best motor would be for a 24V 40ah battery?

 

[fechter]

How fast do you want to go?
How much total vehicle weight?

There is a tradeoff between speed and range. Higher power motors are more expensive and heavier too.

 

[dimitrib90]

How fast do you want to go?
How much total vehicle weight?

There is a tradeoff between speed and range. Higher power motors are more expensive and heavier too.

As fast as possible. Range doesnt have to be long because I am riding only 5 or 6 miles. I want it to go zoom zoom though so that I can get to my school quickly. I was thinking an rc motor but no I really have no idea.

 

[TPA]

can your battery handle high c rate?

 

[The Stig]

Going zoom zoom on a bicycle is not such a good idea on the roads... what kind of speeds are you talking about?

 

[swbluto]

RC motors are kind of out on the jury right now(We're still experimenting with them), but they'll definitely get you to relatively high speeds on roads. The only problem is that you'd need a custom gearing for your bike and the feasibility of that depends on your mechanical skill, aptitude and perseverance.

Hmmmm... now that I'm playing with my simulation program, it seems like the highest speeds you can expect on any set-up is around 25-35 mph(With the higher side corresponding with lower internal resistance for your battery; I assumed it was about .1 ohms and that got about 30) at 24v. Maybe if you used multiple Out-runner motors, you could go faster, but you'll have to use the right gear ratio to extract the maximum speed(and altering gear ratios with hub motors is practically impossible.).

I have a feeling I'm missing something, though. Didn't Craig Uyeda get like 40+ mph on absurdly low voltages like 24?

Hmmm... my program assumed an 80 amp current limit(your battery is 2C, right?), so assuming a maximum of ~20volts*80amps*.85efficiency = 1360 output watts. That would seem to correspond to about 35ish mph, so I guess that result isn't so unexpected.

 

[dimitrib90]

RC motors are kind of out on the jury right now(We're still experimenting with them), but they'll definitely get you to relatively high speeds on roads. The only problem is that you'd need a custom gearing for your bike and the feasibility of that depends on your mechanical skill, aptitude and perseverance.

Hmmmm... now that I'm playing with my simulation program, it seems like the highest speeds you can expect on any set-up is around 25-35 mph(With the higher side corresponding with lower internal resistance for your battery; I assumed it was about .1 ohms and that got about 30) at 24v. Maybe if you used multiple Out-runner motors, you could go faster, but you'll have to use the right gear ratio to extract the maximum speed(and altering gear ratios with hub motors is practically impossible.).

I have a feeling I'm missing something, though. Didn't Craig Uyeda get like 40+ mph on absurdly low voltages like 24?

Hmmm... my program assumed an 80 amp current limit(your battery is 2C, right?), so assuming a maximum of ~20volts*80amps*.85efficiency = 1360 output watts. That would seem to correspond to about 35ish mph, so I guess that result isn't so unexpected.

I think that my battery can do 2C but my BMS can only do 1.5C. 35mph is pretty much zoom zoom on a bicycle for me. I am sending the cells to doctorbass to test so that we can see what the discharge rate of cammys battery could do if the BMS was really good.

But back to the motor, 35mph is awesome. Just tell me how and Im there.

 

[TylerDurden]

24V 40Ah seems better suited for moderate (20mph) speed and generous range.

A system that drives the wheel through gearing could provide more speed on the flats, but retain the torque needed for hills.

Another option is a rig like Kurt's: http://www.endless-sphere.com/forums/viewtopic.php?f=3&t=4936&st=0&sk=t&sd=a
Perhaps 24V would be slower then 'zoom' but having two (or more) motors might permit larger sprockets on the motors for more speed.

 

[dogman dan]

volts = speed so you wanted a 48v 20 ah. Oh well. If you are handy, a new bms and some work can make it into a 48v. My bike that does 24 mph at 36v, only does about 12 at 24v. You won't be zooming without gearing to help.

 

[fechter]

A brushed Etek motor can go pretty fast at 24v. Very heavy and expensive though. A Scott motor might be another 24v option. Still very big and not very efficient.

RC motors have a lot of promise but the gear reduction would be quite challenging.

Another crazy idea would be several MY-10xx geared brushed motors in parallel all driving the same chain.
http://www.electricscooterparts.com/motors.html

 

[dimitrib90]

A brushed Etek motor can go pretty fast at 24v. Very heavy and expensive though. A Scott motor might be another 24v option. Still very big and not very efficient.

RC motors have a lot of promise but the gear reduction would be quite challenging.

Another crazy idea would be several MY-10xx geared brushed motors in parallel all driving the same chain.
http://www.electricscooterparts.com/motors.html

How many is several? What kind of RC motor with the right gearing would work?

 

[dimitrib90]

volts = speed so you wanted a 48v 20 ah. Oh well. If you are handy, a new bms and some work can make it into a 48v. My bike that does 24 mph at 36v, only does about 12 at 24v. You won't be zooming without gearing to help.

I could do it but its way too much work. I was thinking of getting another 24V 40ah battery and series them together but I dont think that I can do that with cammy's BMS's.

 

[fechter]

volts = speed so you wanted a 48v 20 ah. Oh well. If you are handy, a new bms and some work can make it into a 48v. My bike that does 24 mph at 36v, only does about 12 at 24v. You won't be zooming without gearing to help.

I could do it but its way too much work. I was thinking of getting another 24V 40ah battery and series them together but I dont think that I can do that with cammy's BMS's.

Sure you can. You just need to put diodes across the ouput wires to protect the BMS's.

 

[dimitrib90]

volts = speed so you wanted a 48v 20 ah. Oh well. If you are handy, a new bms and some work can make it into a 48v. My bike that does 24 mph at 36v, only does about 12 at 24v. You won't be zooming without gearing to help.

I could do it but its way too much work. I was thinking of getting another 24V 40ah battery and series them together but I dont think that I can do that with cammy's BMS's.

Sure you can. You just need to put diodes across the ouput wires to protect the BMS's.

Do I charge them separately?

 

[fechter]

Yes, they are charged separately. Depending on the charger, you may be able to charge both at the same time without disconnecting them from each other (2 chargers).

 

[dimitrib90]

Do you think I could serial 8 A123 batteries together with my 24V 40ah cammy battery. My A123 battery is 26.4V and 2.3ah.

 

[fechter]

You could, but you'd want to connect a wire from each cell junction so the BMS works for the A123s. You'd end up with a 42.3Ah battery. Not much gain, but could allow higher current peaks.

 

[dimitrib90]

You could, but you'd want to connect a wire from each cell junction so the BMS works for the A123s. You'd end up with a 42.3Ah battery. Not much gain, but could allow higher current peaks.

Sorry for the confusion. I meant could I series the two batteries together to get a 48V 21ah battery?

 

[dogman dan]

Yes, but not for long, and you will want a bms for the a123's so you don't overdischarge them. 2.3 ah will go fast, when I tried some similar thing with some nicad toolpacks, they went dead in about a mile. I would help you climb one hill though, if that is what you need.