60V or 72V setup with 36V 500W motor?

[0037]

Hello,

Wondering if anybody has either a 60V or 70V setup on a 36V motor?

I have a 36V 500W motor and currently use a 48V 600W controller with a 48V system.
This gives me a top speed of around 40km/h, which is plenty for a bike.

I've been looking into possibly building a motorcycle-type frame and using this motor
for it, but was wondering if anyone has experience with upping the voltages higher
than 48V.

Basically, I'm looking to up the voltage to possibly get more speed for my new project
and was wondering if the motor can handle more than 48V.

[ccbreder]

I know what you mean. 36v, 500w and I go faster than the bike can stop. plan to use a regen controller for the braking assistance. But back to your question. Have you considered using two wheels, front and rear. Less chance of burning the coils in the motor. There is some limit to how much we can over-volt an e motor.

[architect]

Hi,

I would say that the 36v 500w motor can do more that 48v but I believe u would have to do a mod to the 48v controller.... and I would say an upgrade of the wiring to the motor would be a must.

I have a 500w 36v motor and have increased the volts to 42v without changing the controller and everything seems to be working fine. The motor does not even get hot and the existing wires are fine.

I would agree that adding a front and rear motor to your next project would be ideal seeings that the frame will have extra weight.

All up I think it sounds interesting and u have to keep us posted on how your project turns out..


Cheers

[biohazardman]

I am running mine on 48v also.  It gets plenty warm in the summer on hills and at slower speeds.  I know I read someone is running it on 60v but don't remember where I saw it. You can get an Infineon  http://endless-sphere.com/forums/viewtopic.php?f=2&t=5713  or C-lite controller  http://endless-sphere.com/forums/viewtopic.php?f=9&t=10107  for the 60V and then find the wireing diagram  http://endless-sphere.com/forums/viewforum.php?f=2  probly on Endless-sphere forum.

[Barry]

Have you considered using two wheels, front and rear. Less chance of burning the coils in the motor. There is some limit to how much we can over-volt an e motor.

Two wheels will not increase your speed. It will only increase your accelration and hill climbing ability (torque).

Lift your wheel into the air and give it full throttle. This will show you how fast your wheel can possibly turn. Two motors cannot turn any faster than one.

[0037]

Thanks for the info so far.  I've looked into controllers and found both 60v and 72v controllers, so that wouldn't be the problem.  (thanks for the links on endless-sphere biohazardman) I was wondering about the wiring into the motor and if it could handle the increased voltage. 

I could easily rewire the hall effect sensor wires to something of a smaller gauge (if they fit through the axle opening), and rewire the phase wires if need be, but was wondering if the motor might then overheat at the higher voltages.

I suppose if I limit the amps into the motor (28A being the original amp limit) then I might be okay, so I'd have to watch out for quick acceleration from a dead stop to not exceed 28A for too long.  Hmm, lots to think about.

[Perbear]

I could easily rewire the hall effect sensor wires to something of a smaller gauge (if they fit through the axle opening), and rewire the phase wires if need be, but was wondering if the motor might then overheat at the higher voltages.

Several ebikers have filled motor housing half full with oil to get better cooling, good corrosion protection and for minimotor, sufficient lubrication. This is a bit risky since using the wrong oil could harm parts inside the motor, but if you search the web you will find sucess stories there.

With 50% of the volume filled with the correct oil compatible with your motor parts and non-foaming, cooling of your motor will improve quite a lot with only a slight increase in frction loss (at moderate speed).

[ccbreder]

Don't you think two motors = more torque? I think more torque, same weight resistance would = more speed. I agree free wheel RPM would be max speed.
i haven't tried two wheels but I am thinking about doing.

[Bikemad]

Don't you think two motors = more torque? I think more torque, same weight resistance would = more speed.
I agree free wheel RPM would be max speed.
I haven't tried two wheels but I am thinking about doing.

I definitely agree, two motors will give twice the torque and a faster top speed than one, but it will still be slower than the unloaded wheel speed.

The max rpm for the Magic Pie is shown as 480 rpm which is presumably it's free spinning (no load) speed. A 26" wheel turning at 480rpm would give a road speed of approximately 37mph, but a bike fitted with this wheel will not be able to reach 37mph on a flat road because of the drag caused by frictional/rolling resistance and wind resistance. As your speed increases, so does the drag (but at a much higher rate).

I would expect the bike to go 25% faster using two motors than it did with just one, providing the battery can put out twice the amps.
(But the battery will last less than half as long!)

In other words, if a single motor can reach 24mph on the level you should be able to achieve 30mph by using two.

If it were possible to ride a bike fitted with a single Magic Pie motor in a vacuum, with no frictional losses, it would attain the maximum speed of 37mph! (Without pedalling)

Alan

A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW).
With a doubling of speed the drag (force) quadruples. Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, four times the work done in half the time requires eight times the power.

[Barry]

On my 36v ebike my front wheel will spin 25.5 mph in free air. I can go 22 mph on level ground, no wind, either direction. (I weigh 120 lbs.)

If I were to put two motors on my bike I would probably go faster than 22 mph but slower than 25.5 mph. Hardly worth the second motor and the extra power to run it.

I am sure it would climb any hill but that would of course come at the cost of more power consumption.

[ccbreder]

I wonder if two motors would use less energy than one motor climbing the same hill. I am thinking greater efficiency.
Also separate battery and controller, same throttle.

[Gregte]

I wonder if two motors would use less energy than one motor climbing the same hill. I am thinking greater efficiency.
Also separate battery and controller, same throttle.

Each motor individually would use less energy but combined they would use more. This is due to the frictional loss in the motors which would be doubled. Also, the inefficiency of the motors (all motors have it) would also be doubled.

The total efficiency would be less. Why would you think it would be greater? Efficiency is input/output.

[Bikemad]

I wonder if two motors would use less energy than one motor climbing the same hill. I am thinking greater efficiency.
Also separate battery and controller, same throttle.

Each motor individually would use less energy but combined they would use more. This is due to the frictional loss in the motors which would be doubled. Also, the inefficiency of the motors (all motors have it) would also be doubled.

The total efficiency would be less. Why would you think it would be greater? Efficiency is input/output.

        Greg, I'm not saying you're wrong, but please take a look at the following and let me know if I've got it wrong:

        I've used actual dynomometer information for the Golden Motor 36v 500w motor in this example:

• A single motor drawing a current of 17.8 Amps has an output of 451.5 Watts and is only 70.7% efficient.
   
• A single motor drawing half this current (8.9 Amps) has an output of 260 Watts and is 81.1% efficient.
   
• Therefore two motors drawing a combined current of 17.8 Amps would produce 520 Watts of power. (Also 81.1% efficient)
   

According to my calculations, two motors would give an extra 15% power output for the same input as a single motor.

Therefore I'm convinced that two motors can be more efficient than one!

As these are brushless/gearless motors, the only frictional loss comes from the actual bearings which a standard non-motorised hub also has!

If the same battery is used for both motors, the only negative side would be the extra weight of the second hubmotor, speed controller and wiring.

A bike ridden on the flat would definitely be more efficient and also slightly faster using two motors limited to half power instead of one motor at full power!
(I'm not so sure about steep hills though.)

I wonder if there any volunteers out there who would like to put my theory to the test and report back with their results?

Alan
 
ps. Efficiency is output/input

[Dolfino]

Firstly, if you're afraid that you might put too much voltage into the motor, then why don't you just get a bigger motor. you could buy a 48V motor and then overvolt that. Secondly, If possible, you could increase the wheel size, larger circumference= more distance rolled per revolution.

[Bikemad]

Firstly, if you're afraid that you might put too much voltage into the motor, then why don't you just get a bigger motor. you could buy a 48V motor and then overvolt that.

Running a 36v motor at 60v (66% overvolted) should produce more power and a higher rpm than running a 48v motor at 60v (25% overvolted) as long as the windings can cope with the extra heat generated.

Secondly, If possible, you could increase the wheel size, larger circumference= more distance rolled per revolution.

By increasing the wheel size you also increase the gearing, making it harder for the motor to turn the wheel under load.
This would also mean less torque would be available at the wheel.

Putting an extra large chainwheel on a non-electric bike does not necessarily mean that you can go any faster on it. You would also need to be able to exert greater pressure on the pedals but at a slower pedalling rate (cadence) to achieve the same top speed as the original lower gearing. The more power you can apply - the faster you will go!

The only reason you need to change down to a lower gear when climbing a hill is because your legs cannot generate enough power to maintain the same speed that you can achieve on the flat.

Things are never quite as simple as they may appear!

Alan