Going from 52v to 72v on a Phaserunner - effects on lower speed performance?

[Bush mechanic]

Not quite sure how to phrase this, so hopefully this makes sense:

I've been running 52v (14s) on everything for years, but have the opportunity to buy a new battery and the itch to reach higher speeds! 52V gets me to a little over 40km/h on the Gmac, Bafang, and Crystalyte motors in a 26" wheel in the windings I have, but I really want the ability to hit mid 50km/h at a minimum to navigate certain sections of road, where having cars come up behind me is quite hazardous.

The Phaserunners I have easily handle 72v obviously, but here is where I need some help. I don't always want to ride fast, especially on my cargo bike if I have the kids - I rarely exceed 25km/h , however, that low speed often requires high torque/current.

At the moment I can hapily switch my 52v batteries between commuter (high speed) and cargo (low speed) bikes and it feels like a good compromise, but I am wondering if there is going to be any significant issue raising this to 72V? I typically use the cargo bike wide open throttle to climb hills carrying kids/tools/groceries, often only hitting 15-20km/h at full throttle up short steep sections, would I be likely to notice any issues if I try the same thing with a 72V battery?

I'm just having a bit of trouble getting my head around the operation of the controller in the situation, trying to visualise how it converts the input voltage and current into phase output.

 

[amberwolf]

When you up the voltage on a system without changing the motor/etc., then the system will be proportionally faster at full system voltage to the motor (under whatever control situation causes that; I'd normally say full throttle, but the PR is a torque-modulating system, not speed-modulating, so it doesn't work quite that way).

It doens't mean you have to *use* that speed--you can limit the system speed in the PR setup suite if you have a top speed limit you must stay under, but if you do want the faster speed, you'll get proportionaly more, meaning 72v / 52v = 1.38x the speed you have now (assuming you also have the power to reach that speed under the specific riding conditions at that moment). That turns your 40km/h to 55km/h, given the power to do it.

Because it's current modulating, using full throttle gets you full phase current, and at a higher voltage that should mean more power, assuming that this current at this voltage doesn't exceed the power limit of the system. Meaning, let's say you ahve the current limit set to the 90A battery current max, with 72v. That's 72v x 90A = 6480W; I don't think your motor or controller can do that.

At only 52v x 90A that's 4680w, which the mtoor and controller also can't do, so you're still limited in power to whatever the max is anyway. No change there.

If you have temperature rollback based on the motor's temperature enabled, it'll help protect that; I think the controller is automatic (you just have some control over the limit).


I will advise you that hte GMAC gets noisier quick the faster you spin it. In my 20" wheel on the back of the SB Cruiser trike, at only 20mph, it's pretty dang noisy because of the RPM it's spinning those gears at. A larger wheel at the same speed should be proportionally quieter.


Anyway, you have control over the current fed to the motor via the throttle, assuming you're using direct throttle control of it.

If you are using a Cycle Analyst to modulate the throttle signal to the controller, it has a mode that uses the speed sensor to have throttle modulate speed, so that you use the throttle to control the proportion of max speed you want and the CA sends whatever is needed to the controller to maintain that speed under whatever conditions you're under at that moment.

Personally, I prefer the torque (current) control; it feels more natural, so that's what I am using (though I'm using cadence-PAS to modulate this via the CA rather than a physical hand-throttle for almost all of my riding).

 

[Bush mechanic]

Thanks Amberwolf, I think I can get my head around it, and I think it is a workable setup!

I will advise you that hte GMAC gets noisier quick the faster you spin it. In my 20" wheel on the back of the SB Cruiser trike, at only 20mph, it's pretty dang noisy because of the RPM it's spinning those gears at. A larger wheel at the same speed should be proportionally quieter.

This ^ is sady something I am finding even at 40km/h in a 26 inch wheel, I am really torn in two directions about the GMAC. On the one hand it is a clever inovation making a "DD" geared hub (well, you know what I mean...) but on the other hand I'm not really sure it is a move in the right direction for most people. Batteries have more capacity than they used to, brake pads are pretty damn cheap, and I have in fact found the locked clutch with regen to be annoying when living up on a hill, so you cannot in fact use e-braking when initially descending the hill with a fully charged battery!

And yes, there is the noise- from day one my GMAC has had a very annoying metallic rattle when coasting ie. not under power , which I have never been able to identify. And the whine when reaching 40kmh....wow yeah it is pretty bad. Sadly I do not have a plain MAC to compare the GMAC to, to identify whether the original non-locked clutch is quieter. I am assuming it would certainly be quieter when not under power, not sure about high revs under load, this might just be the noise you get with heavy duty straight cut gears (the helical gears on the Bafang G310 are just beautiful in comparison!)

Thanks for the reply!

 

[calab]

Gears will make noise, I have an old eZee type geared and a mid drive from cyclone and a mystery brushed w/ l.a. batt. that I subsequently broke. Might be the material of the gears you could look into.

 

[amberwolf]

This ^ is sady something I am finding even at 40km/h in a 26 inch wheel, I am really torn in two directions about the GMAC. On the one hand it is a clever inovation making a "DD" geared hub (well, you know what I mean...) but on the other hand I'm not really sure it is a move in the right direction for most people. Batteries have more capacity than they used to, brake pads are pretty damn cheap, and I have in fact found the locked clutch with regen to be annoying when living up on a hill, so you cannot in fact use e-braking when initially descending the hill with a fully charged battery!

The extra torque you get for lower startup current is nice. Also getting that kind of braking torque is nice--a DD won't have the same startup or braking torque for the same current--it will take a significantly higher current (bigger controller and battery) to do the same thing, and heavier bigger DD motor as well.

The catch is the noise from the gears (and that's true of any geared hub using straight-cut gears; there are a few helical-cut gear motors but they either have narrower gears (hence lower torque limits) or wider housings or narrower stators/magnets (lower torque generation), because they have to have side-support bearings (forgot the actual term) against the sideloading of the gears against the casing/etc.

The other catch is, as you note, a locked clutch or clutchless geared hub has no way to disengage it for coasting, so....the higher torque is then applied to any drag loading of the motor too.

And yes, there is the noise- from day one my GMAC has had a very annoying metallic rattle when coasting ie. not under power , which I have never been able to identify. And the whine when reaching 40kmh....wow yeah it is pretty bad. Sadly I do not have a plain MAC to compare the GMAC to, to identify whether the original non-locked clutch is quieter. I am assuming it would certainly be quieter when not under power, not sure about high revs under load, this might just be the noise you get with heavy duty straight cut gears (the helical gears on the Bafang G310 are just beautiful in comparison!)

Any freewheeling motor would be quieter when not under power. If it has the clutch between the casing and the gearing it will be virtually silent (most motors have the gearing between the casing and the clutch, so you still hear the gears; they're just not loaded).

 

[Bush mechanic]

All good points, thanks Amberwolf. I wonder if packing the gears with extra grease, or alternatively going down the ATF or oil filled route would have an effect on gear noise, simply by absorbing some of the noise and reducing audible resonance. I know it's done for cooling but I imagine it might reduce noise too.

 

[amberwolf]

All good points, thanks Amberwolf. I wonder if packing the gears with extra grease, or alternatively going down the ATF or oil filled route would have an effect on gear noise, simply by absorbing some of the noise and reducing audible resonance.

Heavily packing with grease doesn't change it that much (a tiny bit); tried that. :lol:

Oil filling might make some difference, but to really dampen it I think you'd have to at least nearly fully fill the case, and that would take some doing to seal the bearing/axle/case interface, and the bearings themselves, well enough to prevent weeping. Might also have some issues keeping it from weeping out thru the spaces in the wiring conductors.


If you could get it to stick permanently with *no* risk of coming loose, you could put acoustic dampening (dense rubber, etc) on all the large "flat" metal surfaces of the motor (inside or out, though inside would help more it would be tougher to safely do), especially including the space between the flanges, and the flats of the side covers. This would dampen the vibration of the covers and casing. The catch is that this will also insulate against thermal transfer, and the motor will get hotter, faster.

The axle will also carry out some of the noise, and transfer it to your frame, which will vibrate, and at some speed/load points the frequency of the vibrations will probably resonate with the frame and amplify it. (this is common with trapezoidal controllers and DD hubs, for instance).

 

[Bush mechanic]

Heavily packing with grease doesn't change it that much (a tiny bit); tried that. :lol:

Thank you, probably no need for me to replicate that experiment then!

I've run through all those possibilities in my head and arrived at pretty much the same likely conclusions. I will say that there is a noticeable difference going from cheaper trap controllers to the phaserunner, there really is less 'growl' at low RPM. My old 408 was terrible for that on a cheap 9-fet I ran for a long time.

I guess this has all deviated a bit from the original topic, but I appreciate the input! I have in fact ordered the 72V battery after playing around a bit more with the simulator and reading a few more posts, I'm feeling pretty confident now about the performance under various conditions. At this stage, keeping all else equal on my cargo bike with the 10T GMAC, it will basically "extend" the full level of thrust I can achieve from where it currently rolls off at 10kmh, to about 20km/h when represented visually using lbs-thrust instead of Nm (I always find the thrust metric this easier to imagine in real worl terms).

As most of my riding is in that speed range I think it should make a useful difference - hopefully will be able to post confirmation of this within a week (@offGridDownUnder , have ordered from Cap Rouge , looking forward to the 72V 20s3p Samsung 40T - thanks for the suggestion in previous thread a couple of months ago)

 

[amberwolf]

Thank you, probably no need for me to replicate that experiment then!

Yeah, I just tried it the week before last (or the one before that?) when I asked Grin what grease was safe to replace the contaminated grease I had to clean out of my GMAC at the beginning of this month.

The SB Cruiser : Amberwolf's 2WD Heavy Cargo Trike & Dog Carrier

clamping / pinching dropouts both ends, tight and flat to axle both ends both sides, no nuts needed on either side (have one on outside anyway just because there's axle length for it) is hubmotor with solid axles, can't see anything like qr axles or hollow ones? shear was at shoulder of axle...

endless-sphere.com

I asked at the same time if they had any ideas for quieting it down, but basically without helical gears, there's not much..."overpacking" with grease was really about it. (Generous was the word used, IIRC). So to carry that to it's most extreme, I basically filled the entire planetary/sun/ring gearspace with grease, all the way up to almost touching the motor bell. I'm sure the gears pushed some of that out so it's all over the bell now, too. Since I have three tubes of this grease, I thought about packing the whole casing and motor with grease, but decided not to, as it would probably negatively affect motor operation.

I've run through all those possibilities in my head and arrived at pretty much the same likely conclusions. I will say that there is a noticeable difference going from cheaper trap controllers to the phaserunner, there really is less 'growl' at low RPM. My old 408 was terrible for that on a cheap 9-fet I ran for a long time.

It does make a big difference; not just sinewave but actual FOC should do the most to quiet a system down, since it creates a current waveform based on actual motor characteristics and response to input.

The ex-A2B Ultramotor DD hubmotor I'm now running on the trike in place of the GMAC is silent even with heavy braking except at the lowest speeds; it's only an 8-pole motor vs the more common 23 so the growl is probably much more noticeable than it would be with a more typical motor.

 

[Bush mechanic]

without helical gears, there's not much

Thanks, once again that has saved me going down that track, I think it is pretty clear that it is a case of diminishing returns trying to quiet the beast down.

Interesting point about FOC, to be honest I had not really thought about it much beyond delivering sine wave output, but that is a good point that it tailors the phase current to the field which I suppose in theory should smooth the transition between poles.

 

[batteryGOLD]

I've been running 52v (14s) on everything for years, but have the opportunity to buy a new battery and the itch to reach higher speeds!

most controllers handle "overclocked voltage"
a conttroller rated for 14S battery, could easy support extra volts usin a 16S battery (check internal input capacitors voltage)
58.8V to 67.2V this is about just 15% voltage increase overclock..

those extra volts will give more performance, keeping linear performance during all discharge voltage window and does not make the veicule slower when running at lower battery soc %

make sure U know what U are doin, do not burn a controller or a motor, use some electronics knowledge before any experiment..
is a 15% overclock safe?

 

[batteryGOLD]

see what people do to xiaomi m365 trotinete / patinete
some crazy people add one or two extra elements in serial w 10S battery
voltage rise from 42V to 46,2V or 50,4V ( this overclocks voltage by 20% )

is 20% extra voltage safe for a xiaomi m365 controller? any performance reports / reviews from people?

 

[batteryGOLD]

meaning 72v / 52v = 1.38x the speed you have now (assuming you also have the power to reach that speed under the specific riding conditions at that moment). That turns your 40km/h to 55km/h, given the power to do it...

this is a 38% overclock voltage (careful to not explode controller capacitors, but controller may continue running even w exploded capacitors!)
U can't simply use voltage racio to convert into speed racio 40km/h to 55km/h..

the dificulty of speed increases fast because air friction
math is not linear, incrementing 38% at voltage battery will not give more 38%speed!!

if the controller handles extra 38% voltage increment, and is not limited speed, so maybe from 40km/h U could get at max 50km/h or maybe less.. don't know.. anyone do this experiment and post results!

 

[E-HP]

this is a 38% overclock voltage (careful to not explode controller capacitors, but controller may continue running even w exploded capacitors!)
U can't simply use voltage racio to convert into speed racio 40km/h to 55km/h..

the dificulty of speed increases fast because air friction
math is not linear, incrementing 38% at voltage battery will not give more 38%speed!!

if the controller handles extra 38% voltage increment, and is not limited speed, so maybe from 40km/h U could get at max 50km/h or maybe less.. don't know.. anyone do this experiment and post results!

Right around 29%

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[amberwolf]

U can't simply use voltage racio to convert into speed racio 40km/h to 55km/h..

the dificulty of speed increases fast because air friction
math is not linear, incrementing 38% at voltage battery will not give more 38%speed!!

That is already covered in what I said, if you read my post.

 

[Bush mechanic]

a conttroller rated for 14S battery, could easy support extra volts usin a 16S battery (check internal input capacitors voltage)

Not actually sure what caps the pahserunner has but I think it's rated for 90v so no danger at 72 even hot off the charger. The little 20A I am currently running on my commuter has 63V caps - rated for 14S (my 52v is 58.4 off the charger and has never caused any issues), but there really isn't any headroom, so I certainly would not suggest anyone tries this without at a minimum opening your controller and having a look at the capacitors!

 

[batteryGOLD]

Not actually sure what caps the pahserunner has but I think it's rated for 90v so no danger at 72 even hot off the charger. The little 20A I am currently running on my commuter has 63V caps - rated for 14S (my 52v is 58.4 off the charger and has never caused any issues), but there really isn't any headroom, so I certainly would not suggest anyone tries this without at a minimum opening your controller and having a look at the capacitors!

check example
the xiaomi m365 (runs a 10S 42V battery) controller main capacitor 63v and the MOSFETs are 75V_max 80A STB75NF75.

at good hardware design, the capacitors used are not running at limit voltage.. (42V using 63V caps is different design than a 58.2V running w/ 63V caps.. (this happens at low cost controllers, components are almost at the limit specifications..)

using a capacitors near voltage limits will decrease capacitor life time, and reduce capacitance of capacitor.. but it works..

no one should overvoltage or overclock any hardware! if better performance wanted, just buy a new better hardware!
or just do it for experiment / testing purpouses! many people are doin overvoltage/overclocks, soo more danger in tha world!

 

[batteryGOLD]

anyone remember SAFETY when riding scooter, patinetes,etc . remember, u'r not inside a metal car, so body is only defensive against riding circustances/environment !

google source:
Kinetic energy is energy possessed by an object in motion. The earth revolving around the sun, you walking down the street, and molecules moving in space all have kinetic energy. Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K.E. = 1/2 m v2.

some physics.. means that if U fall at 50km/h will be much worst that fall at 40km/h.. remember, K.E depends on tha square of tha speed..
imagine some people broke some bones when falling at 5km/h walking.. so imagine at speed ten times more, 50km/h.. crazyyy

cited "where having cars come up behind me is quite hazardous."
is very danger to mix anything with cars (only a train or truck beats a car..), those have a metal shield & U have a body and a soul!

Everyone, think twice before go to road, and choose the correct veicule for tha circustances, or choose a safe route!

 

[chuyskywalker]

no one should overvoltage or overclock any hardware! if better performance wanted, just buy a new better hardware!
or just do it for experiment / testing purpouses! many people are doin overvoltage/overclocks, soo more danger in tha world!

Bro. He's on a phaserunner, it is *designed* to run any voltage from a 24v pack up to a 72v pack interchangeably.

Please clue in before continuing to spout off.

 

[Bush mechanic]

cited "where having cars come up behind me is quite hazardous."
is very danger to mix anything with cars (only a train or truck beats a car..), those have a metal shield & U have a body and a soul!

I don't disagree man, but I gotta get around. I'm not advocating riding crazily but there are times it's safer to just get through a spot quickly so you have better visibility and room to manoeuvre. If I had it my way we'd all be riding giant lizards, growing our own vegetables, keeping chickens and listening to music but the only alternative I can identify right now is building a higher power e-bike.