Hello everyone, I am thinking about adding an extra hoverboard motor (friction drive) to my functioning ebike to pump extra voltage to the controller when riding. My bike has a 36v lithium battery 10ah, with a 1000w brushless hub motor and an oversize contoller (48-60v). I am hoping to use the hoverboard motor with a 3 phase bridge rectifier to increase voltage and improve speed, adding to the 36v battery supply. Any help appreciated, Mick.
Secondary friction motor for increased voltage
- Thread starter MxusMick
- Start date
DanGT86
100 kW
I think your best bet will be to just add another 10Ah battery pack in series to get to the voltage you want. You could also add a DC/DC converter to simply step up the voltage rather than rigging up a whole mechanical device plagued with frictional and conversion losses. Even that seems more complex wasteful and troublesome than simply adding more battery.
What you are proposing sounds dangerously close to a perpetual motion machine. Fundamentally its possible to make a mechanical device to step up voltage but I dont see how you could feed that back to the supply in any useful way.
What you are proposing sounds dangerously close to a perpetual motion machine. Fundamentally its possible to make a mechanical device to step up voltage but I dont see how you could feed that back to the supply in any useful way.
Chalo
100 TW
Yeah, don't do that. If you only have one battery, that's your system voltage. You can't magically run your bike on 36V and then use your bike's motion to run a generator that makes a higher voltage which you feed into the same power bus. In practice, the battery's voltage will clamp the output voltage of the generator. So you'll have extra drag, noise, weight, and wear, but no extra voltage.
Get a better battery. That means both higher voltage and more Ah capacity. You should not be running a 1000W motor and controller on a 36V10Ah battery.
Get a better battery. That means both higher voltage and more Ah capacity. You should not be running a 1000W motor and controller on a 36V10Ah battery.
...early morning.... coffee just starting to kick in... I see the words, and individually they make sense, but not really in that order.
Well, the motor won't 'pump extra voltage TO your controller' - unless you somehow set it up as a generator... but then you have your original motor driving this motor - as mentioned above, that sounds like 'perpetual motion'. No good here.
OK
Sort of falls apart here again. Sounds like you plan to be using the hoverboard motor as a generator? ...and rectify the output? Again - no good. This is 'perpetual motion' if you plan to use one motor to drive another as a generator.
Yes, abandon this plan while you're ahead and re-read the three rules of thermodynamics... 1) You can't come out ahead 2) You can't break even 3) You can't not play the game
I'm also not completely sure about 'adding another battery pack in series' - that would be 2x 36V, which would get you up to 72V. This is FAR excess of the motor rating (assuming it also matches the battery rating) and also 12V above the controller rating, so that might tend to let magic smoke out of the system pretty quick. You could possibly swap out the 36V battery for a 48V version which may give some modest gains, assuming the motor can handle it. If the motor is rated closer to the controller, (60V) you could also look to increase the battery to that point - again, provided all other components can handle it.
But at any rate, the voltage increase needs to come from extra battery, not hooking a motor to act as a generator to feed back to the motor.
OK - fair enough.MxusMick said:
Well, the motor won't 'pump extra voltage TO your controller' - unless you somehow set it up as a generator... but then you have your original motor driving this motor - as mentioned above, that sounds like 'perpetual motion'. No good here.
OK
Sort of falls apart here again. Sounds like you plan to be using the hoverboard motor as a generator? ...and rectify the output? Again - no good. This is 'perpetual motion' if you plan to use one motor to drive another as a generator.
Yes, abandon this plan while you're ahead and re-read the three rules of thermodynamics... 1) You can't come out ahead 2) You can't break even 3) You can't not play the game
I'm also not completely sure about 'adding another battery pack in series' - that would be 2x 36V, which would get you up to 72V. This is FAR excess of the motor rating (assuming it also matches the battery rating) and also 12V above the controller rating, so that might tend to let magic smoke out of the system pretty quick. You could possibly swap out the 36V battery for a 48V version which may give some modest gains, assuming the motor can handle it. If the motor is rated closer to the controller, (60V) you could also look to increase the battery to that point - again, provided all other components can handle it.
But at any rate, the voltage increase needs to come from extra battery, not hooking a motor to act as a generator to feed back to the motor.
DanGT86
100 kW
Are we sure it would be perpetual motion? He is not trying to produce more power than the total input here. He is just trying to change its voltage.
Im thinking of this scenario:
-2wd bike with different winding hub motors in each wheel.
-2 separate controllers
-slower winding motor is regen only.
Assuming you could wire it up such that the low voltage battey doesnt get murdered by the high voltage regen. Wouldnt the equilibrium cruising speed fall somewhere between the 2 winding speeds?
Its still not a practical or useful idea but is it possible its just a rotary voltage converter and not violating any laws of physics?
I feel like I'm probably neglecting to consider the drag from the generator here. Its an interesting thought experiment.
Im thinking of this scenario:
-2wd bike with different winding hub motors in each wheel.
-2 separate controllers
-slower winding motor is regen only.
Assuming you could wire it up such that the low voltage battey doesnt get murdered by the high voltage regen. Wouldnt the equilibrium cruising speed fall somewhere between the 2 winding speeds?
Its still not a practical or useful idea but is it possible its just a rotary voltage converter and not violating any laws of physics?
I feel like I'm probably neglecting to consider the drag from the generator here. Its an interesting thought experiment.
jimmyhackers
10 kW
- Joined
- May 11, 2015
- Messages
- 600
what your suggesting is like putting your hand behind your back to push yourself up a hill.
the complexity, weight, and cost of doing all of that.....you may aswell just get a better battery/esc.
the only feasable way it would be usefull is if you could disconnect/connect it, and have it more as a regen during braking or going down a hill.
the complexity, weight, and cost of doing all of that.....you may aswell just get a better battery/esc.
the only feasable way it would be usefull is if you could disconnect/connect it, and have it more as a regen during braking or going down a hill.
Mick here, I would be running the hub with a 36v battery and then wiring a hoverboard motor with 3 phase bridge rectifier to the controller for an added boost under motion. The hoverboard motor/ rectifier would be set friction drive style against the rear wheel. 36v battery powered plus whatever the hoverboard motor pumped out at speed, with the larger controller to handle the voltage spike. This seems possible as long as it didnt flood back into the 36v battery.
Chalo
100 TW
Sorry, no. Even if you rectify the generator output, and diode isolate the battery and generator so that they can't backfeed each other, there's an insurmountable problem. The instant the generator's voltage rises at all above the battery voltage, power will stop flowing from the battery. No power from the battery means the bike can only be "powered" by the drag on its own forward motion, so it will slow down until battery power begins flowing. It will never exceed the speed that the battery alone would provide. In fact, such a system would be limited to whatever road speed causes the generator to produce the same voltage as the battery-- so, slower than if you didn't use it.
Chalo
100 TW
E-HP said:
As far as I can tell, putting a bridge rectifier in series with a DC source is pretty much the same as putting it in parallel. When the AC source isn't happening, the DC source will interact with the rectifier as a series of two diodes. But since both sides of the bridge output will be +36V, the AC source must exceed that before any current flows from it.
I appreciate the feedback, I suppose I was going to get 36v from the battery and an extra 20v from a hoverboard motor/ 3 phase rectifier mounted inline. I have a collection of salvage motors, capacitors, magnets, hoping to utilize and a generous collection of 18650s for a bigger battery. Thanks for the advice! Mick
Just like other people said, a friction drive with low turn count CAN allow you to reach higher speeds from same battery, provided it is powerful enough to overcome air resistance it that speed, and your battery can provide it.
Otherwise, indeed, this is just a perpetual motion machine you are trying to create
Just use one of those boost converters from aliexpress, if you are willing to sacrifice a few percent of efficiency:
https://aliexpress.com/item/4000581345533.html
Otherwise, indeed, this is just a perpetual motion machine you are trying to create
Just use one of those boost converters from aliexpress, if you are willing to sacrifice a few percent of efficiency:https://aliexpress.com/item/4000581345533.html
