OK another technical question

[OxygenJames]

Just for the hell of it (OK to see if I could make the think go faster) - I tried out a new controller for my oxygen bike.

It said it was 500W 'unrestricted'. OK. Fair enough. I wired it up and did not connect the two white wires together (if you know the answer to this question I think you'll know which white wires I am talking about) - and sure it went faster than the old controller - but only on the throttle - pedalling it didn't seem to make much difference (and in fact going back to the original oxygen controller and disconnecting those two white wires sure seemed to perk the throttle top speed up on that - to the point where I dont think there's actually much difference between the two controllers at all).

So - already slightly confused in South London.

Now here's the bit I really got me - I have two batteries for my Oxygen - one a 14.5a and one a 10a - so I play around with it and no matter which one you put in - they both make it go about the same speed (with the 'unrestricted' controller too) - to me it would seem the 14.5 should be putting near 522W through the motor and the other one only 360W - so how come?

And................... neither one makes the bike go as quick as my other electric bike which is a Burisch - which has supposidly a 250W controller and a 9A battery!

No I dont understand.

Very confused in South London.

 

[banbury frank]

Hi The AH off a battery are nothing to do with speed or power Just range it is the storage capacity off the battery AH x volts =watt hours

What makes a big difference is VOLTS as all motors are rated at RPM per volt ( revs per minute )

Frank

 

[flecc]

As Frank says, volts for speed pro-rata, double the volts and you'll double the speed, if there's enough power for the speed doubling.

More Amps delivered and consumed give more power (and heat) but without speed gain, so good for hill climbing.

 

[banbury frank]

Hi Amps are delivered by the controller DON'T get confused by AH ( amp hours ) from the battery

The 2 are not connected ( if you get the pun )

Frank

 

[OxygenJames]

Hi The AH off a battery are nothing to do with speed or power Just range it is the storage capacity off the battery AH x volts =watt hours

What makes a big difference is VOLTS as all motors are rated at RPM per volt ( revs per minute )

Frank

OK - I think I am getting this - so basically if I want the bike to go faster I need the controller to deliver more current to the motor - or more potential difference (volts). I get it. I think I blame the guy who sold me the new controller who seemed to suggest that with the bigger capacity battery I would get a faster bike - obviously not so - I should know all this I passed O level Physics with a B - though that was a few years ago.

So these motors are critical - as in how much current can they take and at what volts - maybe my Burisch goes faster because the motor is more efficient? Is that theory valid - the Oxygen has an 8Fun motor and the Burisch has a 'Synergydrive' whatever that is - but the Burisch is definitly quicker even though it has a 250W rated controller whereas I just put an 'unrestricted' 500W in the Oxygen.......

Any thoughts anybody?

 

[OxygenJames]

Hi The AH off a battery are nothing to do with speed or power Just range it is the storage capacity off the battery AH x volts =watt hours

What makes a big difference is VOLTS as all motors are rated at RPM per volt ( revs per minute )

Frank

And now I'm confused again......... you say all motors are rated at RPM per volt (revs per minute). Huh? I've seen them rated RPM (revs per minute) - but not revs per volt (which would be RPV?).

Or was that a typo?

 

[OxygenJames]

OK - I am probably showing how not-bright I am in this conversation but so be it.

Here's a few interesting facts:

(bear in mind my main purpose behind all this has been to make my Oxygen bike go as fast as my Burisch bike - OK?)

My Burische controller says its 'peak protection' current is 12a (which would mean 432W max output right?)

The original Oxygen controller says 16a max (576W max right?).

The new 'unrestricted-500W' (that I bought for the Oxygen thinking it might make it go as fast as the Burisch) controller says 14a max (that would be 504W)

It would appear the original controller from oxygen will supply more current to the motor than the 'unrestricted-500W' new one I just bought for it (not that I am complaining because in the process I am learning all about how these darn bikes work!).

But anybody who cares to shine any light on this go ahead.

PS. Its very good to have learned for example that the Ahr of the battery has nothing to do with how fast it will make the motor go - only the volts and controller can do that.

 

[banbury frank]

Hi I will give you an example our standard motors are wound at 9.6 rpm per volt our fast motors are wound at 12.5 rpm per volt 2 reasons if fitted in a 20 inch rim you need higher rpm or our main use is for the Ghost kit IE 2 motors we have so much toque we just build for top speed IE 38 + MPH

so 9.5 or 12.5 X the volts off the Battery X the diameter off the tyre in inches X 60 for minutes to hours divided into miles From inches = MPH

 

[NRG]

OJ the parameter is Kv of the motor for RPM per volt.

A larger Ah battery can make a bike feel stronger on hills as the voltage is less likely to sag under load, more Ah effectively raises the C rating of the battery. iE if a 10ah batt is rated at 1c continuous the same celled battery in a 20ah configuration would be capable of 2c (capable of delivering twice the current) so the volts are less likely to sag under load.

 

[banbury frank]

Ok I will now throw in another variable BMS ( battery management the circuit board in the battery pack that controls input IE charging and OUTPUT ) It is no good uprating the controller if the BMS will not cope as you will open the throttle and the battery It will shut down until you disconnect from the load IE controller and it will then reset Most 250 watt bikes the BMS will be max10 Amps continues so fitting a new more powerful controller will give problems

on the bike you have the battery and controller and motor will all be made to work together

Our BMS are set to 30 Amps continues with a peak off 60Amps

Frank

 

[Old_Dave]

And now I'm confused again.........

Lol

What Frank was trying to get across* was that the manufacturers rated RPM is achieved at a set number of volts.

The RPM of the motor 'can' be increased at an amount which is related to an increased voltage (though it may not be linear but lets pretend it is) = ( [SUP]rated [/SUP][SUP]rpm[/SUP]/[SUB]rated volts[/SUB] ) * new volts = new RPM.

The ( [SUP]rated [/SUP][SUP]rpm[/SUP]/[SUB]rated volts[/SUB] ) now used as RPV although being a kinda fictitious number is of use

* I think

 

[OxygenJames]

Hi I will give you an example our standard motors are wound at 9.6 rpm per volt our fast motors are wound at 12.5 rpm per volt 2 reasons if fitted in a 20 inch rim you need higher rpm or our main use is for the Ghost kit IE 2 motors we have so much toque we just build for top speed IE 38 + MPH

so 9.5 or 12.5 X the volts off the Battery X the diameter off the tyre in inches X 60 for minutes to hours divided into miles From inches = MPH

Thanks Frank.

It must be the motor that's making the difference - thats my conclusion so far - the Oxygen's motor is getting just as much oomph (from the battery and the controller) - but delivering less speed than the Burisch. That has to be the answer.

 

[OxygenJames]

Ok I will now throw in another variable BMS ( battery management the circuit board in the battery pack that controls input IE charging and OUTPUT ) It is no good uprating the controller if the BMS will not cope as you will open the throttle and the battery It will shut down until you disconnect from the load IE controller and it will then reset Most 250 watt bikes the BMS will be max10 Amps continues so fitting a new more powerful controller will give problems

on the bike you have the battery and controller and motor will all be made to work together

Our BMS are set to 30 Amps continues with a peak off 60Amps

Frank

Ha!! Just when I thought I'd gotten clear!

So the battery itself may not allow more than 10a to come out of it huh? Wow. The things I am learning...... mind you on the Oxygen site it says 576W 'peak only during climbing or start' so I am assuming the battery management bit is allowed more than 10A output at those moments.

 

[flecc]

on the Oxygen site it says 576W 'peak only during climbing or start' so I am assuming the battery management bit is allowed more than 10A output at those moments.

Bear in mind that suppliers have to be circumspect about quoting powers, since the law says 250 watts maximum continuous power. The continuous capability is usually more than quoted.

 

[banbury frank]

Hi OK now the next problem Cable size I will explane amps and volts simply so you can see them

If we take a bucket and try to fill it with a hose 1/4 inch diameter the volume coming out is AMPS the length of the amount jetting out is volts IE Pressure so how do fill the bucket faster well if we turn up the pressure IE volts it will fill faster Or make the hose diameter larger IE larger cable

SO if you have thin cables and try to increase the amps thy wont GO .To the extreme the cables and connectors will melt

Again your bike will be designed to all work with thin wires they do the job there we designed for

Frank

 

[Deleted member 4366]

If I can step in here to make it a bit clearer.
Maximum speed depends on which motor you have. Even some motors of the same type that look the same from the outside are different inside, so you can get different versions.

Changing a controller won't change the speed unless your original one were under-powered. In you case the Oxygen 16 amp controller is strong enough to give good speed on the flat. Changing to a 14 amp one will give less speed.

If you want more speed, you have to change the battery to a higher voltage one. A 48v one with the same case shape will slot straight in and give a 30% increase in speed. Your 36v controller should manage 48v, but if it goes pop, at least you have a spare.

If you read the Beastamatic thread, it should give an idea of how all this works.

 

[Ajax]

Your 36v controller should manage 48v

Is there a way to tell for sure?
And failing that, is there a way to prevent the controller going 'pop fizz'?

 

[jackhandy]

So, James - Does your bike climb hills any more strongly with the bigger controller?

 

[NRG]

Is there a way to tell for sure?
And failing that, is there a way to prevent the controller going 'pop fizz'?

The only way to know for sure is to open the controller up or rely on somebody else's experience!

If opening the controller up you need to check three things:

1) The maximum rated voltage of the FET's used to drive the motor phases
2) The voltage rating of the capacitors
3) The input, output voltage differential of the 3.3v or 5v regulator circuit is not exceeded

 

[Deleted member 4366]

So, James - Does your bike climb hills any more strongly with the bigger controller?

He didn't get a bigger controller. He got a weaker one - down from 16 amps to 14 amps.

The only way to be sure if your controller can handle 48v is to open it and look inside to read the writing on those three key components just like NRG says.