Does"over volting" a brushless direct drive motor result in

[ebikedelight]

Higher speed and better low end power/ torque or just a higher speed ?

Lets say you have a 1000 watt - 48 volt brushless hub motor / direct drive and you run it on a 60 volt battery/ controller . Will the user notice better power on takeoff and for hill climbing or is it just gonna have more speed on takeoff thru mid range and top end ?

Ive gotten a few different opinions on this and wasnt sure which opinion was correct.

 

[teslanv]

It will depend on the controller's settings.

generally higher voltage = faster top speed, all other things being equal.

To Increase torque (and thus acceleration) you need to increase the amperage from your controller. This can be done with a shunt mod, or just getting a higher powered controller.

 

[ebikedelight]

It will depend on the controller's settings.

generally higher voltage = faster top speed, all other things being equal.

To Increase torque (and thus acceleration) you need to increase the amperage from your controller. This can be done with a shunt mod, or just getting a higher powered controller.

So one should see a increase in torque/ power, just by doing a shunt mod alone , as long as the controller can handle the mod and the battery can put out the increased amps without any change in battery voltage needed?

This means using a 1000 watt / 48 volt brushless direct drive hub motor , will gain noticeable power/ torque just thru shunt mod alone ?

 

[r3volved]

Voltage has a direct relationship with motor rpm. Increase volts and increase top speed.

Amperage has a direct relationship with motor torque. Increase amps and increase acceleration.

Motors are rated in watts. V x A = W
Pushing past a motors rated wattage will increase heat and reduce efficiency. How much energy you can safely push through your motor and controller varies by setup.

 

[ebikedelight]

Voltage has a direct relationship with motor rpm. Increase volts and increase top speed.

Amperage has a direct relationship with motor torque. Increase amps and increase acceleration.

Motors are rated in watts. V x A = W
Pushing past a motors rated wattage will increase heat and reduce efficiency. How much energy you can safely push through your motor and controller varies by setup.

Thank you...

So If one has a 48 volt / 20Ah battery ..with a controller that can only handle 30 amps...purchasing a new controller only, that can handle 50 amps , will make a noticeable increase in torque/ power for hill climbing ability { as long as the battery/motor can handle the output } ?

 

[dnmun]

depends on the battery. a li ion 48V pack of 15Ah would have a hard time pushing 50A.

 

[r3volved]

Your max amps from the battery is your Ah x C rate (V is irrelevant in this case)
A typical 2C battery @ 20Ah can push 40A.
Battery amperage is limited by the BMS if you're using one.

 

[teslanv]

So one should see a increase in torque/ power, just by doing a shunt mod alone , as long as the controller can handle the mod and the battery can put out the increased amps without any change in battery voltage needed?

This means using a 1000 watt / 48 volt brushless direct drive hub motor , will gain noticeable power/ torque just thru shunt mod alone ?

Yes, that is true. However you do risk blowing the FETs by allowing too much current to flow through your controller.

 

[MadRhino]

Hey ! Do the math: Amps being equal, double the voltage means double the watts. When you raise the voltage without changing controller Amp setting, you are adding power proportionally. That is why we run higher voltage in the first place, because it is the best way to feed more power. You will soon realize that: passing some critical point, to achieve better speed you need power. We don't care how fast a motor spins unloaded, we want it to spin LOADED. Then, the result is heat and that will determine the limits of your system.

 

[hydro-one]

u will draw more amps at higher speed and continue to accelerate , bemf wont kill it

 

[friendly1uk]

Hey ! Do the math: Amps being equal, double the voltage means double the watts. When you raise the voltage without changing controller Amp setting, you are adding power proportionally. That is why we run higher voltage in the first place, because it is the best way to feed more power. You will soon realize that: passing some critical point, to achieve better speed you need power. We don't care how fast a motor spins unloaded, we want it to spin LOADED. Then, the result is heat and that will determine the limits of your system.

Do you realise that doubling the voltage won't give you double the power at average motor rpm's
Double the voltage means it takes half the time for full current to become present, which the controller will then regulate. So the gain in power comes from getting it turned on quicker.
At higher rpm's where the motors generation capabilities are starting to hinder current flow, Higher voltage can ensure we still reach full current.

 

[MadRhino]

Higher voltage is the first step to better performance. It is cheap both in cost and weight.

Once you start going high Amp, it is when you begin to upgrade everything, fry and break components, need to build a better bike because it got too heavy, find the limits and build better again. Costly, yet freaking fun.

 

[wesnewell]

If you increase the voltage it will increase both acceleration and top speed for the simple reason the motor will see more watts, VA=W. If you increase just the amps, acceleration increases because A will be higher, but it will not noticeably increase the top speed except when under heavy load like hills.

 

[d8veh]

Definitely, you get more torque as well as more speed when you increase the voltage. I've done many tests to show it. It's because each pulse going to the motor has a higher amplitude, so more energy per pulse. If you increase the voltage, you probably won't need to solder your shunt.

You can also get more torque by soldering a bit of your shunt without changing the voltage. Top speed will be the same. You should only do it if your battery can meet the higher discharge rate. If your motor is really struggling on some hills, increasing the current, paradoxically, can give it an easier time, allowing it to run more efficiently and cooler, but if the hill is still making it struggle, melt down will come quicker.

 

[ddk]

If you increase the voltage it will increase both acceleration and top speed for the simple reason the motor will see more watts, VA=W. If you increase just the amps, acceleration increases because A will be higher, but it will not noticeably increase the top speed except when under heavy load like hills.

Definitely, you get more torque as well as more speed when you increase the voltage. I've done many tests to show it. It's because each pulse going to the motor has a higher amplitude, so more energy per pulse. If you increase the voltage, you probably won't need to solder your shunt.

You can also get more torque by soldering a bit of your shunt without changing the voltage. Top speed will be the same. You should only do it if your battery can meet the higher discharge rate. If your motor is really struggling on some hills, increasing the current, paradoxically, can give it an easier time, allowing it to run more efficiently and cooler, but if the hill is still making it struggle, melt down will come quicker.

correct!
increasing voltage=increasing power.
= benefit with both acceleration and top speed.

If other said about the same I'm too lazy to read the whole thread :lol:

oh... and over-volting a geared-hub motor has the same effect.

 

[dogman dan]

Volts x amps = watts. More watts, is always going to be more power, more torque.

So increase either volts or amps, and you will get more torque. Most of us choose to increase both! 8)

But if you just want a faster take off, a shunt mod could be all you really need. Increase the amps, if your battery can take it.

If you want more speed, increase the volts first. It will still improve torque some too.

 

[Punx0r]

Torque is only proportional to phase current - voltage and wattage is irrelevant.

Increasing voltage does enable the controller to better overcome the back EMF of the motor and push more current at the same motor speed, giving more speed. But this is just because you've increased the no-load speed of the motor and if you're still travelling at the same road speed, you're operating at a lesser fraction of the motor's no load speed (max. power is at 1/2 no-load speed, and falls off either side to zero).

 

[dogman dan]

Yes, as usual I give too simple an answer. And I should have pointed out that since adding 300w more works, it doesn't mean it's a good idea to add 3000 more watts.

Definitely, if you add voltage, the motors no load speed just went up, and presumably with more watts you can get more speed. Say you started with 800w, and wind resistance stops you from going any faster, towards your no load speed. Perhaps 25 mph is your max speed.

Even keeping the volts the same, with no increase in no load, 300 more watts could mean you can overcome wind resistance better, and have the power to get a tad closer to your motors no load speed, with a load.

So increasing just amps, can in some cases result in a few mph speed. But more volts, increasing the motors no load speed generally works better.

And like I said, if you ran 48v 20 amps, you'll really love the increase if you switch to 72v 30 amps.

 

[MadRhino]

Torque is only proportional to phase current - voltage and wattage is irrelevant.

Well, try feeding 3V 500A phase current
Then try feeding 100V 100A

You will see the difference of torque between 1.5 Kw and 10 Kw of power.

 

[arkmundi]

Once you start going high Amp, it is when you begin to upgrade everything, fry and break components, need to build a better bike because it got too heavy, find the limits and build better again. Costly, yet freaking fun.

Has not happened to me yet, knocking on wood sound, and no that would not be fun for me, though at times I too am a masochist. Rather than torture myself, I tortured the forum, with question after question, until I had a grasp of how to do a good build, that would serve my purpose, not break and give me many years of enjoyment. FYI, its not a this or that, but the BALANCE of components that matter. Often upgrading a component that was underrated will result in a measurable improvement in performance W = V * A is an equation of relationships and all those relations matter and proportionally. W = motor, V = battery, A = controller + wires. You don't, for instance, want to increase watts without also proportionally increasing volts and amps, or vice-versa. Its still a mystery. Do you know what electricity IS? IS? The unknowable universe is vastly strange. Quark, quark sounds....

 

[MadRhino]

Once you start going high Amp, it is when you begin to upgrade everything, fry and break components, need to build a better bike because it got too heavy, find the limits and build better again. Costly, yet freaking fun.

Has not happened to me yet, knocking on wood sound, and no that would not be fun for me, though at times I too am a masochist. ...

That is the beauty of building our own. We all have different goals, requirements and preferences. When I started, I was sure I'd be very happy with 40 Mph. Then it soon became 50 Mph, and more power. Passing the 60 Mph was not that bad. Always trying to achieve better acceleration and lighter weight, yet keeping the bike a good off road ride, that is costly. Every time, I say I'm gonna be happy with this one and stop building new bikes, but I soon find myself making plans to achieve better. At least I don't feel the need to build faster, but I still hope to hit the power that will make me say: it is enough for me.

 

[friendly1uk]

Torque is only proportional to phase current - voltage and wattage is irrelevant.

Increasing voltage does enable the controller to better overcome the back EMF of the motor and push more current at the same motor speed, giving more speed. But this is just because you've increased the no-load speed of the motor and if you're still travelling at the same road speed, you're operating at a lesser fraction of the motor's no load speed (max. power is at 1/2 no-load speed, and falls off either side to zero).

Nobody seems to get it. They think VA=W outside of dc resistive circuits.

 

[dogman dan]

God knows this moron will never understand the why of it. I just go into a brain freeze at some point.

But for sure, I know a 36v 20 amps bike rides ok, but I feel a 48v 20 amps bike rides nicer to me. The true sweet spot for my needs is right around 2000w, 48v 30 amps. I'm too old and weak now to really enjoy a 40 mph bike, but a strong pull to 30 mph I do like a lot!

If you have the cheap dd motors, like a 9c, smaller muxus, etc, they tolerate 2000w of power just fine without meltdowns.

 

[Punx0r]

Dammit. Sorry all, I made a typo before. Corrected in bold...

Torque is only proportional to phase current - voltage and wattage is irrelevant.

Increasing voltage does enable the controller to better overcome the back EMF of the motor and push more current at the same motor speed, giving more [strike]speed[/strike] TORQUE. But this is just because you've increased the no-load speed of the motor and if you're still travelling at the same road speed, you're operating at a lesser fraction of the motor's no load speed (max. power is at 1/2 no-load speed, and falls off either side to zero).

No need to apologise, Dogman. It's hard to get your head around some of this stuff. I still struggle and have to keep thinking it through.

Torque is only proportional to phase current - voltage and wattage is irrelevant.

Well, try feeding 3V 500A phase current
Then try feeding 100V 100A

You will see the difference of torque between 1.5 Kw and 10 Kw of power.

Neg. This is possibly confusing battery voltage/current with phase voltage/current. If the motor's resistance is low enough to permit 500A at 3V then on 100V/100A the controller will reduce the voltage to limit the current to 100A and make five times less torque in the process (and have the potential to spin 33 times faster).

Motor resistance = 3/500 = 0.006 ohms. At 100A limit: phase voltage = 100 x 0.006 = 0.6V

Think about it: you're quoting a difference in power, but power is torque x speed. Either can be increased to increased the power. Therefore increased power does not necessarily indicate or require an increase in torque.

 

[d8veh]

The controller doesn't reduce the voltage. It controls the current. The battery voltage is standing at the FETs. All the controller can do is open and close the FETs, which allows the current to flow. You could talk about the average voltage that the motor sees, or you could talk about the average current. The result is the same, though it's the current that is interrupted by the controller, not the voltage reduced.