CYC Photon Gen 2?

[hindesite]

Goes 40 now and probably more if I get a longer stretch of road

My Gen1 has run over 60kph but not even at full power (throttle only, since this is MTB with low gearing). I don't even run it at 40kph - not due to heating, but it is just too fast draining the battery.

You should get way more than 40mph if your gearing is suitable.

 

[pomah]

The lightest.bike mid drive is actually ~1.75kg.

Bafang sets a low bar on quality and power density/efficiency and it's always been possible to do many times better.

This is an Astro 3210 mid drive.. the motor itself is about 2.35lbs.. add associated hardware and you have maybe 10lbs in total.
The power to weight ratio is approx 4x that of a BBSHD..

.. that's circa 2011, and VERY expensive back in the day.. today the cost of this power density density is way lower..

Just to show you what's possible, power density wise

It's all nice, but we are comparing apples to oranges:

I do not care for a BBSHD, I want a BBS01, 250-500W capable small mid-drive motor. I'm sure that CYC could do it, in an even smaller package than the current photon.

 

[neptronix]

It's all nice, but we are comparing apples to oranges:

I do not care for a BBSHD, I want a BBS01, 250-500W capable small mid-drive motor. I'm sure that CYC could do it, in an even smaller package than the current photon.

I'm in the same position but i want 1-1.5kw. I know it's theoretically possible
Closest thing to that today is the lightest.bike mid drive.

 

[maiz]

I'm in the same position but i want 1-1.5kw. I know it's theoretically possible
Closest thing to that today is the lightest.bike mid drive.

Maybe the upcoming proton?

 

[gundroid101]

Almost certainly a mix of different chain and sprocket wear - usually newer chain on old sprocket, those small cogs wear really fast, especially on ebikes.

I’m thinking this might be the case since I used a new ebike chain. Haven’t thoroughly inspected my 11T cog but the bike is only a few months old. I don’t think it being an ebike really matters since it happens even under no motor power, and there was a long period of time the issue had temporarily gone away. Another review said “on the high end of the torque spectrum it definitely still suffers from some of the sprag clutch issues, I was able to get mine to start slipping in the highest gear” just like mine happens only on the 11T. But it’s possible it could just be worn

 

[gundroid101]

I think 40mph is the limit for my setup. Tested again, 6 laps on a 0.5mi straight (the voltage started getting so low I was losing about 3mph off top speed), one way had a 6mph tailwind and got me 39-40.3, then on the way back against the wind I got 39.3-39.6. After 37mph it accelerates so slow to 40 that it’s just fighting for crumbs. The cyc app speed actually seems to be fairly accurate maybe just 0.5-1mph slower. Usually on my throttle and pedal assist tests there’s no difference, and here it was pure ghost pedaling so didn’t bother with it. Airing up my tires, sitting a bit more aerodynamic, and locking out suspension made no difference from my last test.

Peak temps: motor 60.9C, controller 29.6C
Weather: 12.2C

Also right before the end of the lap the voltage would drop 2.8-2.9v drawing ~37 amps before going back up to normal according to the app, nearly 3v. Is this normal for a barely used 3 month old molicel p42a battery?

 

[hindesite]

I do not care for a BBSHD, I want a BBS01, 250-500W capable small mid-drive motor.

That's what I want, too. That's why I have the Photon and am so disappointed that CYC have ceased production of that configuration.

There is a bigger picture here, too. More jurisdictions are moving to examine and limit DIY ebikes - and since most areas have quite low power allowances, limiting the larger Gen2 Photon to 250W is actually the worst of possible choices. The original Photon would probably work just fine at 250W limited.

 

[gundroid101]

That's what I want, too. That's why I have the Photon and am so disappointed that CYC have ceased production of that configuration.

There is a bigger picture here, too. More jurisdictions are moving to examine and limit DIY ebikes - and since most areas have quite low power allowances, limiting the larger Gen2 Photon to 250W is actually the worst of possible choices. The original Photon would probably work just fine at 250W limited.

I usually stay around 250 W when pedaling on flats. With my setup, anything above 500 W tends to feel like ghost pedaling. The higher power modes definitely help on steep hills, but if you’re reasonably fit and don’t mind taking it slow, you really don’t need that much power. That said, I do use the full 2 kW on flats sometimes just to keep up with traffic, it feels safer that way. Personally, I don’t think the weight savings from a smaller motor would make a big difference, especially since a bigger motor tends to be more thermally robust. For me, ground clearance is the main thing I care about.

 

[Curufinwe_wins]

I usually stay around 250 W when pedaling on flats. With my setup, anything above 500 W tends to feel like ghost pedaling. The higher power modes definitely help on steep hills, but if you’re reasonably fit and don’t mind taking it slow, you really don’t need that much power. That said, I do use the full 2 kW on flats sometimes just to keep up with traffic, it feels safer that way. Personally, I don’t think the weight savings from a smaller motor would make a big difference, especially since a bigger motor tends to be more thermally robust. For me, ground clearance is the main thing I care about.

Its hard for me to reconcile not using much power on hills but then using 2kw on flats... to keep up with 25mph traffic, I'm normally much below 400W combined human+motor, and for 35mph, that would probably still be under 2kw since I can do it at all on my bbs02 bike, which tops at 1200W. Meanwhile while yeah I can climb a 10% grade in a granny gear with only 250W total, that doesnt make it a good experience at all.

Ground clearance is a binary thing, you need enough and anything more is irrelevant. My e-cargo bike has maybe 2-3 inches of ground clearance past my cranks and that is fine for road use and you only turn that bike with pedals flat anyways. For trail I've smacked it once, but anything that hits even a bbs02 sitting low is close enough to risk hitting a chainring. So really for those of us who used acoustic before, if you have never needed a bashguard to date, you have no reason to worry about bottom clearance on a mtb conversion.

 

[gundroid101]

Its hard for me to reconcile not using much power on hills but then using 2kw on flats... to keep up with 25mph traffic, I'm normally much below 400W combined human+motor, and for 35mph, that would probably still be under 2kw since I can do it at all on my bbs02 bike, which tops at 1200W. Meanwhile while yeah I can climb a 10% grade in a granny gear with only 250W total, that doesnt make it a good experience at all.

Ground clearance is a binary thing, you need enough and anything more is irrelevant. My e-cargo bike has maybe 2-3 inches of ground clearance past my cranks and that is fine for road use and you only turn that bike with pedals flat anyways. For trail I've smacked it once, but anything that hits even a bbs02 sitting low is close enough to risk hitting a chainring. So really for those of us who used acoustic before, if you have never needed a bashguard to date, you have no reason to worry about bottom clearance on a mtb conversion.

My gearing goes down to 0.7:1. If I’m on that gear and don’t want ghost pedaling I never really go above 500w. But you might be right for higher grades, I just remember I tried 1kw on 30% grade with granny gear and it was too much.

My bbshd could reach 40mph with pas and it had less watts like your bbs02. Difference is on my current setup the gear ratio is low so it needs more watts. And don’t bother pedaling after 30mph unless you have a massive 50T+ chainring.

For ground clearance I get your point if you know exactly what you’re riding and it’s predictable like urban commuting. For trails, more clearance is margin for the unexpected. ‘Enough’ only makes sense when you already know every trail you’ll ride and that it remains consistent, which isn’t realistic.

 

[Curufinwe_wins]

My gearing goes down to 0.7:1. If I’m on that gear and don’t want ghost pedaling I never really go above 500w. But you might be right for higher grades, I just remember I tried 1kw on 30% grade with granny gear and it was too much.

My bbshd could reach 40mph with pas and it had less watts like your bbs02. Difference is on my current setup the gear ratio is low so it needs more watts. And don’t bother pedaling after 30mph unless you have a massive 50T+ chainring.

For ground clearance I get your point if you know exactly what you’re riding and it’s predictable like urban commuting. For trails, more clearance is margin for the unexpected. ‘Enough’ only makes sense when you already know every trail you’ll ride and that it remains consistent, which isn’t realistic.

That gearing sounds about right for 500W to always be a problem. Mine is 0.8 and I'd say 350W is about where I've always started spinning, but thats also my point, unlike top speed gears, we all have higher gears, and we would generally agree that it is easiest to ride bikes moving faster than the slow granny gearing, and we would also agree that the granny gears have the potential to wear very quickly (often aluminum for 1x conversions)... so we can just gear up and move faster for that input power. For myself, I generally prefer climbing at at least 10 mph if I'm not pushing myself to completely minimize motor assist, and that requires gearing of about 1.3 to climb at a comfy 90 rpm cadence (4th from the top on my cassette), and a good bit of power depending on the hill.

Anyways back on topic for this motor. JNO just posted a video where the torque was a bit suspect to me, but I dont know what his gearing range was. The top speed he showed also was irrelevant because its clear the bike was spinning out using only a 38:11 top gear.

 

[gundroid101]

That gearing sounds about right for 500W to always be a problem. Mine is 0.8 and I'd say 350W is about where I've always started spinning, but thats also my point, unlike top speed gears, we all have higher gears, and we would generally agree that it is easiest to ride bikes moving faster than the slow granny gearing, and we would also agree that the granny gears have the potential to wear very quickly (often aluminum for 1x conversions)... so we can just gear up and move faster for that input power. For myself, I generally prefer climbing at at least 10 mph if I'm not pushing myself to completely minimize motor assist, and that requires gearing of about 1.3 to climb at a comfy 90 rpm cadence (4th from the top on my cassette), and a good bit of power depending on the hill.

Anyways back on topic for this motor. JNO just posted a video where the torque was a bit suspect to me, but I dont know what his gearing range was. The top speed he showed also was irrelevant because its clear the bike was spinning out using only a 38:11 top gear.

I agree you’d want to climb faster than granny gear. I haven’t actually needed to use granny gear for climbing yet. Since you spin out even at high grades I’d assume middle cogs are fine.

Just watched the JNO video, it definitely is the gearing. If I’m on granny gear there’s not a hill it can’t climb. I did a hill test video, and that wasn’t even at the lowest gear.

 

[gundroid101]

Just tested my setup in 2 kW mode on flat ground and logged max watts by gear. The motor only reaches the full 2 kW output in the top two or three gears, around a 2.7–3.3 ratio and higher.

That’s completely normal. At lower gears and slower wheel speeds, the motor needs much more torque, which means high phase current. Without enough back-EMF at low RPM to oppose that current, amps can spike into unsafe levels of heat, so the controller limits current to protect the motor. That’s why wattage appears lower in easier gears. On inclines it’s different because there’s real mechanical resistance to overcome, so the current that does flow is actually being converted into torque instead of mostly heating the copper.

The data actually shows my 36 T chainring with an 11–51 T cassette is very well matched to the motor’s power curve. The range is just long enough for the motor to use its full 2 kW before it runs out of RPM. A smaller ring like 32 T would probably hit the current limit sooner and never quite reach full power, even in top gear.

If I went bigger, say to a 42 T, I’d simply trade torque for speed, slower acceleration but slightly higher wheel speed at full power. However, the extra speed would mostly be eaten by aerodynamic drag, since 2 kW already sustains about 40 mph on flat ground. So any top-speed gain would be minor, maybe a couple of miles per hour in short bursts.

In short, the motor isn’t “spinning out.” The gearing already lets it hit its power limit, and any taller gearing won’t add real top speed unless I raise voltage or reduce drag.

 

[neptronix]

how long can you run 2kw cont until it overheats?

 

[gundroid101]

how long can you run 2kw cont until it overheats?

I haven’t pinpointed exactly when it overheats yet, but judging by the final temps from my speed test footage and footage I had today which started at the same temps, you will enter thermal throttling after about a mile of full throttle 2kw. But honestly the performance drop wasn’t bad. After 90C it limits power to 1500-1600w, and then if you keep running it the numbers don’t change. So you can run a chill 33-35mph forever.

 

[raylo32]

But for folks who intend to mostly pedal the 42t might be a better choice since that would let you ride faster without the rider's pedaling cadence spinning out. Maybe not perfect for the motor on throttle, but close enough.

If I went bigger, say to a 42 T, I’d simply trade torque for speed, slower acceleration but slightly higher wheel speed at full power. However, the extra speed would mostly be eaten by aerodynamic drag, since 2 kW already sustains about 40 mph on flat ground. So any top-speed gain would be minor, maybe a couple of miles per hour in short bursts.

In short, the motor isn’t “spinning out.” The gearing already lets it hit its power limit, and any taller gearing won’t add real top speed unless I raise voltage or reduce drag.

 

[gundroid101]

But for folks who intend to mostly pedal the 42t might be a better choice since that would let you ride faster without the rider's pedaling cadence spinning out. Maybe not perfect for the motor on throttle, but close enough.

True, bigger chainrings help with spinning out. A 38T for me probably reaches 28mph pas without really losing useful climbing, but 36T is the most I could fit. Smaller wheels will want taller gearing as well.

 

[gundroid101]

I ran a thermal throttle test on a one-mile strip at 78°F. The motor didn’t hit true thermal throttling until around 1.75 miles, starting from 37°C. Throttling technically begins earlier, around 1 to 1.25 miles, when temps reach 70–75°C, but the drop is minimal (roughly 100 watts). As temps approach 80°C, the power loss becomes more noticeable at around 300–400 watts. By 90°C, output drops 400–500 watts and stabilizes there. I’m not sure how this compares to the Gen 1, but it’s more resilient than I expected, you can push it pretty hard.

That said, whether you should is another story. Sustaining those temps likely isn’t great for long-term durability, so I’d treat it as a short-term burst for keeping up with traffic rather than a regular thing. For consistently higher speeds, I’d recommend running around 1–1.5 kW with a larger chainring and a higher-voltage battery, though CYC support mentioned that moving to 72 V won’t increase RPM headroom much, since 52 V already gets close to the limit, but it would run cooler.

 

[neptronix]

Thanks, this is a pretty efficient stator then, and it seems like it has some good guardrails against blowing up. Not bad!

 

[hillslayer@]

Johnny nerdout posted a test using a 52 and 72 volt battery no real difference performance wise . Only reason to use 72 volts is if you already have one

 

[hindesite]

True, bigger chainrings help with ghost pedaling.

As I understand it, you are most likely referring to "spinning out" rather than ghost pedaling. Ghost pedaling is an attribute of systems without torque sensing, only cadence or rotation sensing so that just rotating the cranks with no effort still produces full motor power for the level setting.

 

[gundroid101]

As I understand it, you are most likely referring to "spinning out" rather than ghost pedaling. Ghost pedaling is an attribute of systems without torque sensing, only cadence or rotation sensing so that just rotating the cranks with no effort still produces full motor power for the level setting.

Fixed

 

[gundroid101]

Johnny nerdout posted a test using a 52 and 72 volt battery no real difference performance wise . Only reason to use 72 volts is if you already have one

The only minor benefit would be thermals

 

[hindesite]

Just tested my setup in 2 kW mode on flat ground and logged max watts by gear. The motor only reaches the full 2 kW output in the top two or three gears, around a 2.7–3.3 ratio and higher.

That’s completely normal. At lower gears and slower wheel speeds, the motor needs much more torque, which means high phase current. Without enough back-EMF at low RPM to oppose that current, amps can spike into unsafe levels of heat, so the controller limits current to protect the motor. That’s why wattage appears lower in easier gears. On inclines it’s different because there’s real mechanical resistance to overcome, so the current that does flow is actually being converted into torque instead of mostly heating the copper.

The data actually shows my 36 T chainring with an 11–51 T cassette is very well matched to the motor’s power curve. The range is just long enough for the motor to use its full 2 kW before it runs out of RPM. A smaller ring like 32 T would probably hit the current limit sooner and never quite reach full power, even in top gear.

If I went bigger, say to a 42 T, I’d simply trade torque for speed, slower acceleration but slightly higher wheel speed at full power. However, the extra speed would mostly be eaten by aerodynamic drag, since 2 kW already sustains about 40 mph on flat ground. So any top-speed gain would be minor, maybe a couple of miles per hour in short bursts.

In short, the motor isn’t “spinning out.” The gearing already lets it hit its power limit, and any taller gearing won’t add real top speed unless I raise voltage or reduce drag.

I think there are too many hidden or obscured parameters to draw final conclusions. For example, CYC haven't published curves (nor has anybody else) for the original Photon, and I haven't seen any for the Gen 2 - though that is more likely to be comparable to some of the other inrunner motors. It wasn't possible to compare the original Photon since so few outrunner motors are in production.

It is highly likely that CYC are limiting the rotor rpm, and remember that the 25:1 reduction (necessary because of the lower rotor torque) is about 2x the original, which was almost certainly running at lower than efficient speeds in use. The fact that my Photon seems to achieve higher speeds with essentially similar gearing (34/11-52, 27.5+") would bear this scenario out.

The Gen2 might be significantly more efficient than the original, but without datalogging would be hard to compare.

 

[gundroid101]

I think there are too many hidden or obscured parameters to draw final conclusions. For example, CYC haven't published curves (nor has anybody else) for the original Photon, and I haven't seen any for the Gen 2 - though that is more likely to be comparable to some of the other inrunner motors. It wasn't possible to compare the original Photon since so few outrunner motors are in production.

It is highly likely that CYC are limiting the rotor rpm, and remember that the 25:1 reduction (necessary because of the lower rotor torque) is about 2x the original, which was almost certainly running at lower than efficient speeds in use. The fact that my Photon seems to achieve higher speeds with essentially similar gearing (34/11-52, 27.5+") would bear this scenario out.

The Gen2 might be significantly more efficient than the original, but without datalogging would be hard to compare.

True, I wouldn’t draw any conclusions. Just giving a reference point that my setup basically lets me use as low of a gearing as possible while still accessing the 2kw