CYC PHOTON

[neptronix]

The more you gimp an electric motor vs it's ideal voltage, the more efficiency and power you lose. It may be a 350W nominal motor on 36v :/

 

[nervagon]

The more you gimp an electric motor vs it's ideal voltage, the more efficiency and power you lose. It may be a 350W nominal motor on 36v :/

Without specific manufacturer data and efficiency and performance charts there is only one metric that matters with this particular motor... whatever keeps it cool. Beyond that, how on earth would we know its ideal voltage? The rated voltage is 36V – 52V, but what does that tell us? It is looking like 48V and 52V don't mix with human PAS well.

 

[nervagon]

@neptronix Several motor simulations later, and I fail to see how running a mid drive at 36V is "gimping" it beyond just lowering torque and rpm.

Take this eye-opening comparison with the BBSHD climbing under stress with subpar gearing:


We have less torque and RPM, but the BBSHD melts at 52V, where at 36V final temps are significantly lower. We also have more range for the same number of battery cells/watt hours. We have a negligible 1% drop in efficiency on paper, but we are burning more amps and generating more heat at 52V. If there is an error in this comparison, I would love to know what it is.

And now with a 50T rear cog:



So higher voltage at the same current should always be slightly more efficient, and if we lock the simulator to an exact current, we might see that (we'll do that below)... but is that how these motors really work in practice? Here under full throttle, I am seeing the BBSHD gobble up more amps and build up more heat.

And top speed on a flat:


Here at 36V, the BBSHD perfectly matches a comfortable cadence and class 3 28mph. Again, at 52V, the BBSHD is significantly hotter, and significantly less range. Is there a problem with the GRIN simulator? What am I missing here?

So lets limit both system A and B to 20A and see what happens:


And at 52V at the same current, we are actually running significantly hotter still. And that must be due to internal MTR AMPS being so much higher at 52V. Maybe a product of 2.5 MPH faster as well. But is that 2.5mph worth that 21C degree jump in temps? On the BBSHD that's fine... but on the temp sensitive Photon? And note that the 36V system is MORE efficient in that last graph.

And this is the BBSHD, which used to be the worst matched motor for PAS until CYC said hold my beer.

 

[neptronix]

I'm very surprised the BBSHD responds in this manner. Mid drives that contain multiple sets of gears probably have some other factors in play such as, when you lower the voltage, you also lower the gear friction.

I'm wrong and the reason is because i think in hub motor too much.

 

[Epithemeus]

Here at 36V, the BBSHD perfectly matches a comfortable cadence and class 3 28mph. Again, at 52V, the BBSHD is significantly hotter, and significantly less range. Is there a problem with the GRIN simulator? What am I missing here?

What you're missing is that you are running both at full throttle. Of course the 52v one is melting down, it's going faster and thus using more power. That's not a fair comparison. You can get the same performance from the 52v battery with the bbshd by just by lowering the throttle level till you're at the same speed/rpm as the 36v battery. Which is what I did in the link I sent earlier. (Hub versus mid should make no difference, you can try it yourself, lower the throttle of the 52v side until it matches the rpm of the 36v side) Which had the exact same performance. At a given speed/rpm identical motors will perform identically regardless of voltage. So instead of buying a 36v battery and lowering the power limit to 360w, keep your 52v battery and lower the power to 360w. It will perform identically.

 

[nervagon]

I'm very surprised the BBSHD responds in this manner. Mid drives that contain multiple sets of gears probably have some other factors in play such as, when you lower the voltage, you also lower the gear friction.

I'm wrong and the reason is because i think in hub motor too much.

And look at this one:


36V at 25A and 911W of battery power
vs
52V at 18A and 912W of battery power

36V is more efficient AND putting down more actual power from the motor.

36V MTR PWR 696W
52V MTR PWR 685W

So we are basically only getting better voltage sag relief from 52V and higher RPM. But a high capacity 36V battery will help with that too. For the same amount of cells... 10S, 6P is only 4 more cells than 14S, 4P.

I am beginning to question the 52V hype.

 

[Epithemeus]

And look at this one:

View attachment 354871
36V at 25A and 911W of battery power
vs
52V at 18A and 912W of battery power

36V is more efficient AND putting down more actual power from the motor.

36V MTR PWR 696W
52V MTR PWR 685W

So we are basically only getting better voltage sag relief from 52V and higher RPM. But a high capacity 36V battery will help with that too. For the same amount of cells... 10S, 6P is only 4 more cells than 14S, 4P.

I am beginning to question the 52V hype.

You've chosen a different controller though. The MOSFETs could be higher resistance on one versus the other etc. Unless you're swapping out controllers on the photon you've got to do it with identical hardware.

 

[neptronix]

That actually expected, you've got the throttle lower and the amps lowered ( you're choking it - it's not within it's sweet spot for the given voltage )

That AOT controller also has higher resistance because it has junky mosfets.
Partial throttle also eats a little efficiency so it's not always great to use for comparison.

All motors will perform poorly above a certain voltage. It looks like the BBSHD's sweet spot is right around 48v. That's why we're not seeing a big efficiency drop on 36v. Other motors will vary.

 

[Epithemeus]

Partial throttle also eats a little efficiency so it's not always great to use for comparison.

Talking purely hypothetical but lowering the throttle on a higher voltage setup to get it to the same power/rpm as a lower voltage one would indeed result in some PWM losses but then higher voltage lower amps would result in less I^2R losses. Not sure how the two would cancel. I imagine any difference would be slight and it's definitely not worth buying a whole new battery pack for!

 

[neptronix]

Yes in some cases the reduced amperage draw at mid speed is a plus for your battery which will increase your net efficiency.

This is why i use really huge batteries in all my simulations, i don't want the battery sag to swing the calculation too much - we want to isolate how the motor responds.

 

[nervagon]

You've chosen a different controller though. The MOSFETs could be higher resistance on one versus the other etc. Unless you're swapping out controllers on the photon you've got to do it with identical hardware.

Good catch. Accident on my part.

 

[Gruesome]

Very interesting; so as long as the lower voltage battery can deliver the power, then at the same power battery voltage does not matter to within a fraction of a percent. You are drawing a lower battery current though from the higher voltage battery.

 

[nervagon]

Very interesting; so as long as the lower voltage battery can deliver the power, then at the same power battery voltage does not matter to within a fraction of a percent. You are drawing a lower battery current though from the higher voltage battery.

On the higher voltage battery, you can pull the same wattage from the battery on fewer amps from the battery, but the internal mtr amps end up the same, and same heat is generated in the motor according to the sims.

I think my point is that although a 52V battery allows you to push more power from the same battery amps, it creates a lot more heat in the process, and pushes the RPMs outside of the PAS zone. I can see the advantage for a throttle bike, but I am having a hard time seeing the advantage of 52V over 36V for a small PAS motor like the Photon. I wish they would publish their power curves.

I think I do have a 36V battery out in the garage though. I wouldn't need to go buy one to test the Photon at 36V.

 

[hindesite]

I am having a hard time seeing the advantage of 52V over 36V for a small PAS motor like the Photon. I wish they would publish their power curves.

Maybe that is why CYC didn't design the photon to run up to 72v? It is a different philosophy to their previous more Surron like motors.

I would also like to see the power curves - not because it will change my experience of the Photon, but because comparing BBSHDs is fine, but the Photon is an outrunner and their characteristics may be different.

 

[neptronix]

You can find it's ideal voltage to make maximum power with a dyno, or bench race it as we're doing. Too bad we don't have a model of a photon, but probably a BBS01 on 500w power would be a good substitute.

To my knowledge in ideal situations the BBSHD will be in the 82-83% efficiency range, which is allright. To optimize for heat you also have to be at the right cadence etc.

Yeah in the case of the photon, that cadence is just too high to combine human power the optimal way. It probably has thick / low quality laminations in addition to the easy bake oven thermally decoupled from the case aspect that geared hub motors suffer from.

Too bad the lightest bike mid drive doesn't work for you. It has a close to perfect design for efficiency and heat shedding. $10 of acoustic material would probably be the answer to the sound problem.

 

[neptronix]

ps by adding acoustic material to the bikee mid drive you would be reducing it's heat shedding capability but as we can see it has gobs of it, i was really surprised to see heat making it into your frame due to that mount you designed.

Liquid cooling or less power seems like the saving graces for the photon.

 

[nervagon]

ps by adding acoustic material to the bikee mid drive you would be reducing it's heat shedding capability but as we can see it has gobs of it, i was really surprised to see heat making it into your frame due to that mount you designed.

Liquid cooling or less power seems like the saving graces for the photon.

The Bikee Lightest is a beast of a 4lb motor... a loud beast.

 

[Gruesome]

Just a quick update on my search for a lightweight retrofit motor (which is not going to be the Photon because of the 220mm Q factor), since it might be interesting for other cyclists who feel they are at their physical limit: replacing the crunchy right spindle bearing (by pressing in a new bottom bracket), and replacing the worn out (1% stretch) oil lubricated chain with a new KMC chain that I degreased and waxed, made a much larger than anticipated difference.
A dirty chain should make at most 5% efficiency difference (say, 97% to 92%), no idea about the bottom bracket, but maybe the same? It's not a big difference in maximum speed (due to air drag power loss going with speed to the third power), but at the same speed I believe it brings my heart rate down into a much more comfortable range (assuming output power is directly proportional to heart rate, 10% difference would be like going from 150 bpm to 135bpm), and subjectively it makes a significant difference in how far I can go and more importantly how I feel after a long ride.

So, drivetrain efficiency improvement is maybe something to try, and it really helps not to think in terms of (marginal) speed gain, but as reduction in needed power and therefore heart rate.

Still, it would be nice to enable even longer trips (maybe up the San Gabriel Canyon? that's over 400 Wh just of lifting work!) with an add-on e-drive.

 

[raylo32]

Just got back from another road ride on my Photon bike, 30 miles, 1900 feet of climbing. I got out before it got super hot, but still in the low 80s. To my shock and surprise the motor worked fine, no throttling, no broken bottom bracket, no problem with pedaling RPMs, no small anmals fried on the hot motor casing. LOL. This in spite of all the negativity you might have seen here from one self described weirdo ignored person. Nor did the q-factor make me ride like an arthritic duck as posited by one yeti-sized commenter. IOW, I had an absolutely great freakin' ride.

Here are some pics of the roads we ride. I did not get to the mountain in the photo since it is a little far for my battery and physical condition. I may try that in a couple weeks but will need to carry my range extender battery.

 

[nervagon]

This in spite of all the negativity you might have seen here from one self described weirdo ignored person. Nor did the q-factor make me ride like an arthritic duck as posited by one yeti-sized commenter. IOW, I had an absolutely great freakin' ride.

Welcome, @raylo32 , and thank you for sharing your personal truth. I think you'll find that we've all taken different roads to get here. Some of us trudged up very steep dirt paths on knobby rubber. Some through gentle paved rolling hills on 28mm roadie rubber. Some through wind and rain. Some through treacherous, nasty traffic.

But the important thing to remember is that my truth doesn't threaten your your truth... nor does your experience invalidate another member's experiences. This is a safe space. I think it would be beneficial to re-frame feedback on the Photon outside of this negative/positive paradigm. Such framing can become emotional/spiritual and sometimes lead to fanboyism. If you took a more scientific outlook, you might see my reports as outlier data rather than a negative attack.

But it is appropriate to frame comments as negative/positive once you make them personal by pointing them at other members rather than lifeless motor parts as you have done here. Ironically, you have taken a rather innocuous discussion and made it negative while complaining of negativity. But none of us are perfect. We are here to heal. This is where the healing begins.

 

[biphaeboh]

I want to say thanks to everybody who has contributed to this discussion. I've been on the fence about buying a Photon for the last year or so. I still am on the fence. I appreciate different points of view even if it makes the decision more difficult.
It apparently works for some people and not others. Its good to know under what circumstances it doesn't work well.
Thanks everybody.

 

[nervagon]

I want to say thanks to everybody who has contributed to this discussion. I've been on the fence about buying a Photon for the last year or so. I still am on the fence. I appreciate different points of view even if it makes the decision more difficult.
It apparently works for some people and not others. Its good to know under what circumstances it doesn't work well.
Thanks everybody.

I think it's important to remind everyone that I started out praising this motor because I installed it when the weather was quite cool here in SoCal. And so the expectations I placed on this motor were simply based on how it performed when I first installed it, when it was cold. But once temps rose, I now had a different motor. In the beginning I had people coming at me for praising the Photon, and now I have people coming at me criticizing it. I'm just being honest about my experience with this motor.

If the CYC engineers are lurking in this thread, that's the part that I would want them to pay attention to. That I loved my Photon in early spring, and became sorely disappointed by summer. This was my first seasonal motor.

 

[hindesite]

probably a BBS01 on 500w power would be a good substitute.

Why? The Photon is an outrunner motor which would indicate that there will have been totally different decisions made during design, partly due the the intrinsic higher torque and the heat dissipation problems that go with the configuration.

 

[raylo32]

So I did the firmware update a few weeks ago and am just starting to get back to riding following my hip replacement, which is doing fantastic, and found that my settings seem to have been wiped and everything is back to factory. Anyone else? Not a big deal since I mostly ramped up the throttle to be full power for all the levels in race mode since the only time I use it is for brief beyond pedaling speed runs. Easy enough to go back in and fix that. I haven't looked yet bit was wondering, is there perhaps some way in the app to save those settings before doing updates?

 

[hindesite]

So I did the firmware update a few weeks ago and am just starting to get back to riding following my hip replacement, which is doing fantastic, and found that my settings seem to have been wiped and everything is back to factory. Anyone else? Not a big deal since I mostly ramped up the throttle to be full power for all the levels in race mode since the only time I use it is for brief beyond pedaling speed runs. Easy enough to go back in and fix that. I haven't looked yet bit was wondering, is there perhaps some way in the app to save those settings before doing updates?

I think your experience is standard - my settings always seem to get wiped, which I think is fine if you look at this from a product support POV. I've suggested a few times that the ability to save (and share) our own profiles would be really useful and would offset the reset done by firmware updates. Please, CYC...

The main change I make is to the speed restrictions and to reduce the lower assist settings. Greatly extends battery life.