Bi-Weekly Ebike specific Youtube Video AMAs (with a Watt Wagons bias)

pushkar

Well-Known Member
Saw the video - not sure some answers were correct, or perhaps incomplete.

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You mention higher Voltage isn't needed, or imply that it's pointless. Then minutes later you mention that speed is limited by gear ratio and Wattage. I assume the answer was disingenuous, or maybe just too oversimplified.

For others - gearing helps multiply torque, but each gear's use is limited by the power plant's rpm limit or other mechanical limits. With the controllers being used in ebikes (not boosting Voltage), battery Voltage can limit how fast the controller can spin the motor, requiring a gear-change to lower the rpm back down - this loses torque. If you had a 72V battery instead of a 48V battery, you could theoretically spin the motor 50% faster, keeping more of that higher (lower numerical) gear multiplication in play before requiring a shift. Re-phrased, a higher Voltage battery pack can allow a higher speed in all gears, and with a mid-drive as long as you can either keep up with the cadence, or go throttle-only to spin the crank higher than humanly possible, the higher Voltage pack could give you a couple mph max top speed in all situations, depending on the spacing of the gears. This is far more noticeable if you were to go downhill, as you become rpm-limited rather than drag/power-limited. This is the same reason racers build higher-rpm and higher-geared cars - get more torque to the ground for more rapid acceleration, staying in the lower gears for longer, and more easily fight drag at higher speeds.

Not that we need people going 40mph on an ebike ;) The speed advantage is also noticeable uphill, being able to stay a couple gears down lower while the motor spins away. This can be a 20% speed difference while bogged down in the 10-15mph range (for more widely-spaced derailleurs - I doubt the gain is as large on the 14-speed IGH).

Of course people experience this themselves with a normal bike - you can only pedal so fast, before you need to up-shift. If you hit a hill, you need to downshift to get more torque multiplication at the wheel. Try limiting pedaling to 60rpm and go for a ride, then do the same but limit pedaling to 90rpm; the 90rpm test will have a higher top speed, and likely be a gear lower.
Wattage -
1. What I didn't mention is that Ultra can realistically do only up to 3500W (max power). That is a real world upper bound on motor wattage and is still within the design spec of a 52V pack (at 70/80A). If you drive more than 3500 W, the motor heats up and the controller will shut it down.

2. Further, my understanding is that BMSs are not built to serve under a certain amp draw. e.g. if you get a BMS for a 72V battery, the BMS wont support a discharge rate of 5A or 10A. There is a low draw cutoff. May be someone with more knowledge can comment on why / how that works but that is the case.

Where I am going with this is that for the 72V battery pack, the min discharge rate floor will be higher. So most of the times, it actually wont be able to support a street legal 750W motor config (which can go from 400W to 1200W).

What that leads us to is actually a tier of battery voltages (48 or 52) that are kind of universal for the 500-3500W range. This is for theforseeable future, the ideal pack size. If you have a motor under 500W, you are going to have better performance with a 36V pack since that min discharge rate is lower than the floor of the 48V pack. (which is why bosch uses that). Note early versions of bafang used a 24V pack for 100-150W motors. Then they switched to 36 .. and so on .

So in the wattage performance tier we are in, for all practical purposes, higher voltage is not needed because it doesnt serve the use cases we need to serve. Further, a higher voltage pack will actually restrict our ability to run 750W configs. A 72V version becomes a viable alternative only if we run the motor exclusively at 2500W and above.

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Throttle - no/little ramp up causing drivetrain shock. The controller can be designed to easily control ramp rate though. Just don't give that full power immediately, even if commanded, and ideally have shift-detection to prevent banging gears. Maybe if a person is already going 25mph, give them a more aggressive ramp rate. More feedback from sensors would be nice, but you can get by with just speed. I'd hope the electronic Rohloff shifter in the future would provide better feedback here also, and maybe ease more power in as the speed increases. This is how some fuel and timing tables work in one of my cars.

I still don't understand restricting throttle at higher speeds. Perhaps you're thinking someone may be in a lower-numerical gear at 20mph, and throttling away (legal limit for this on the street). At any speed I can't imagine the throttle being any different than a person ghost-pedaling, other than you have a cadence sensor to help identify what gear they may be in? If so, then what would be the minimum cadence that the controller will allow more than 750W? Is it limited by combination of cadence + speed?

Throttle
1. Most use cases of throttle are to use one from a stand still. Or, riders use a throttle while going uphill (they will be pedaling in the taller gear to gain speed, and then push a throttle without consciously changing the gear). These are typically the cases where most of the unintended damage happens.

2. Yes a throttle can be designed for a gentler ramp up. Riders can also feather the throttle. However most riders just twist the throttle and go. If the bike doesn't move (taller / higher gear), they will twist (push) more and break the top gears. Sending more torque instantaneously. The larger the gear (physically) the lower the breaking torque limit.

3. If you are on a flat surface, you can get to the same speed with a 750W throttle, compared to a 2300W throttle. It will just take a little longer.

4. Once you are in a taller / higher gear at say 15MPH or higher.. you can still throttle on the taller gear with less chance of gear failure.
 

Masejoer

Member
Wattage -
1. What I didn't mention is that Ultra can realistically do only up to 3500W (max power). That is a real world upper bound on motor wattage and is still within the design spec of a 52V pack (at 70/80A). If you drive more than 3500 W, the motor heats up and the controller will shut it down.

2. Further, my understanding is that BMSs are not built to serve under a certain amp draw. e.g. if you get a BMS for a 72V battery, the BMS wont support a discharge rate of 5A or 10A. There is a low draw cutoff. May be someone with more knowledge can comment on why / how that works but that is the case.

Where I am going with this is that for the 72V battery pack, the min discharge rate floor will be higher. So most of the times, it actually wont be able to support a street legal 750W motor config (which can go from 400W to 1200W).

What that leads us to is actually a tier of battery voltages (48 or 52) that are kind of universal for the 500-3500W range. This is for theforseeable future, the ideal pack size. If you have a motor under 500W, you are going to have better performance with a 36V pack since that min discharge rate is lower than the floor of the 48V pack. (which is why bosch uses that). Note early versions of bafang used a 24V pack for 100-150W motors. Then they switched to 36 .. and so on .

So in the wattage performance tier we are in, for all practical purposes, higher voltage is not needed because it doesnt serve the use cases we need to serve. Further, a higher voltage pack will actually restrict our ability to run 750W configs. A 72V version becomes a viable alternative only if we run the motor exclusively at 2500W and above.



Throttle
1. Most use cases of throttle are to use one from a stand still. Or, riders use a throttle while going uphill (they will be pedaling in the taller gear to gain speed, and then push a throttle without consciously changing the gear). These are typically the cases where most of the unintended damage happens.

2. Yes a throttle can be designed for a gentler ramp up. Riders can also feather the throttle. However most riders just twist the throttle and go. If the bike doesn't move (taller / higher gear), they will twist (push) more and break the top gears. Sending more torque instantaneously. The larger the gear (physically) the lower the breaking torque limit.

3. If you are on a flat surface, you can get to the same speed with a 750W throttle, compared to a 2300W throttle. It will just take a little longer.

4. Once you are in a taller / higher gear at say 15MPH or higher.. you can still throttle on the taller gear with less chance of gear failure.

Wattage: Yeah, I understand the motor's max power/mechanical limits and 3kW+ is already more than I thought the Ultra may be able to do, when it was originally released. BMS just depends what you're using. You may be correct in that there are lower thresholds into how more basic/off-the-shelf BMS circuits are designed. I do agree that 72V isn't a need, but 750W in 2nd gear can get you further along under high load than 750W in 5th gear. "In season" (pre-covid commuting) I'm limited to a continuous 250W output via person-power, but uphill I can go faster in a lower gear. The input power didn't change.

Reading your response here, I see now that you were responding to the question specifically in that the Bafang motor is a static part/design, and increasing Voltage will increase current, so you run up against those limitations. With the specific motor you have selected, yes more Voltage is a waste as there's a power limit you can feed it. Same cell count but lower Voltage lets you pull more current from the pack. With a differently wound motor, higher Voltage could help, but this is outside the scope of your specific product; you're limiting the scope of discussion to the exact product you're building, and that your answer wasn't intended to be a general statement about battery Voltage.


Throttle: Are you saying that throttle starts at 750W, but would eventually open up to 2300W? Even 750 starting seems high for my own use case; 750W with lower gearing on an upright bike is already enough to kick up hard from a standstill. I do understand your reasons for limiting, at least down low. Not sure about your statement that "on a flat surface, you can get to the same speed with a 750W throttle, compared to a 2300W throttle" - 2300W on upshift should always go faster, as long as it's actually 2300W (managed Voltage sag) and there's gearing available. Me being taller, with an earlier upright bike I had and with winter gear + saddlebags (big sail), I've had a BBS02 pegged at 1300W at impossible-cadence (more gearing) struggle to get me to 15mph into a flat-elevation headwind. 2300W should be a lot faster than 750W, throttle or not.

I'm just curious what "restricted 750w" actually means. Does ghost-pedaling at 20mph get you more power than throttle at 20mph? I don't think I've received a response to this the last couple times I asked over the last year. Curiosity more than anything - I just want to know how the bike functions, and hopefully be able to re-tune some things for slower ramp rates, and leave the extra power for a couple times a year when it's needed. I'm not trying to impress anyone by kicking up wheelies at a stoplight.
 

BruceBrown

Active Member
Region
USA
City
Kansas City
Ran across this article tonight and thought I’d post since the question of a Gates belt drive came up for the Hydra.

 

Masejoer

Member
Ran across this article tonight and thought I’d post since the question of a Gates belt drive came up for the Hydra.


I like that. Not convinced all the rear suspension pivots would be reliable for thousands of miles a year on a commuter (how often would they need to be replaced with wear and rain?), but always wish I could soften up a commuter more than just a fork and suspension post. Closest I got was a Biktrix Juggernaut Ultra FS, but that thing only wanted to go straight.

I hope to only have belt drive ebikes in the future.
 

Ebiker33

Well-Known Member
Wattage: Yeah, I understand the motor's max power/mechanical limits and 3kW+ is already more than I thought the Ultra may be able to do, when it was originally released. BMS just depends what you're using. You may be correct in that there are lower thresholds into how more basic/off-the-shelf BMS circuits are designed. I do agree that 72V isn't a need, but 750W in 2nd gear can get you further along under high load than 750W in 5th gear. "In season" (pre-covid commuting) I'm limited to a continuous 250W output via person-power, but uphill I can go faster in a lower gear. The input power didn't change.

Reading your response here, I see now that you were responding to the question specifically in that the Bafang motor is a static part/design, and increasing Voltage will increase current, so you run up against those limitations. With the specific motor you have selected, yes more Voltage is a waste as there's a power limit you can feed it. Same cell count but lower Voltage lets you pull more current from the pack. With a differently wound motor, higher Voltage could help, but this is outside the scope of your specific product; you're limiting the scope of discussion to the exact product you're building, and that your answer wasn't intended to be a general statement about battery Voltage.


Throttle: Are you saying that throttle starts at 750W, but would eventually open up to 2300W? Even 750 starting seems high for my own use case; 750W with lower gearing on an upright bike is already enough to kick up hard from a standstill. I do understand your reasons for limiting, at least down low. Not sure about your statement that "on a flat surface, you can get to the same speed with a 750W throttle, compared to a 2300W throttle" - 2300W on upshift should always go faster, as long as it's actually 2300W (managed Voltage sag) and there's gearing available. Me being taller, with an earlier upright bike I had and with winter gear + saddlebags (big sail), I've had a BBS02 pegged at 1300W at impossible-cadence (more gearing) struggle to get me to 15mph into a flat-elevation headwind. 2300W should be a lot faster than 750W, throttle or not.

I'm just curious what "restricted 750w" actually means. Does ghost-pedaling at 20mph get you more power than throttle at 20mph? I don't think I've received a response to this the last couple times I asked over the last year. Curiosity more than anything - I just want to know how the bike functions, and hopefully be able to re-tune some things for slower ramp rates, and leave the extra power for a couple times a year when it's needed. I'm not trying to impress anyone by kicking up wheelies at a stoplight.
On the restricted throttle, I just want to say we had a very lengthy discussion on EBR previously, and there is some legacy tech restriction that carry over. One of them is that if you allow too much torque to the IGH it voids the warranty. It would be especially bad if you had a derestricted throttle with 2300 watts in the wrong gear, there is one gear that is considered the straight gear that would not effect it, but nobody can risk that the end user will always make that happen, or maybe they just forget even if they know. The point is protect your components, yes you can feather it as well, but some might be inclined to gun it, putting the full wattage and torque on every component. One end user with an Ultra, not Watt Wagon complained his ultra was so powerful he kept busting chains, as far as I know the stock throttle with the stock Ultra is unrestricted.
I think Pushkar is playing it safe on this for a very good reason. I would not order the unrestricted throttle, too much risk of killing your components with no warranty.
So with a cassette bust your chains, with a Gates belt bust your IGH
 

Masejoer

Member
On the restricted throttle, I just want to say we had a very lengthy discussion on EBR previously, and there is some legacy tech restriction that carry over. One of them is that if you allow too much torque to the IGH it voids the warranty. It would be especially bad if you had a derestricted throttle with 2300 watts in the wrong gear, there is one gear that is considered the straight gear that would not effect it, but nobody can risk that the end user will always make that happen, or maybe they just forget even if they know. The point is protect your components, yes you can feather it as well, but some might be inclined to gun it, putting the full wattage and torque on every component. One end user with an Ultra, not Watt Wagon complained his ultra was so powerful he kept busting chains, as far as I know the stock throttle with the stock Ultra is unrestricted.
I think Pushkar is playing it safe on this for a very good reason. I would not order the unrestricted throttle, too much risk of killing your components with no warranty.
So with a cassette bust your chains, with a Gates belt bust your IGH

I know the purpose of the throttle restriction, but you're not understanding what I'm getting at. One may limit the throttle to 15A, but that alone doesn't protect the IGH. Through the cadence detection, you're then pushing 45A - much more input torque to the IGH. The IGH doesn't care if you're feeding it 45-50A (~2300W) from the throttle or the pedal-sensing; it will still have all that power hitting it. The "throttle limit" is just preventing people from holding the throttle for 10+ seconds to get up to speed in the incorrect gear. I understand that casual ebike-riders may treat their bikes as a single-speed.

I can easily put it in 14th gear and press down hard on the pedals from a stop. It shouldn't go anywhere, but somewhere the controller is detecting cadence and torque from the pedal. If I put the bike on a stand and just turn the pedals, is the thing going to try to give full power? I'd imagine so, and there's your high torque. It's still getting full power to the IGH - it just accelerates quicker due to lack of load.

I would think the throttle restriction only makes sense below a certain speed; otherwise the workaround once up to speed is to just ghost-pedal for full power.

I haven't seen anything shared about how the controller is programmed, what its curves look like, etc. The hard 750W limit makes me think the archon x1 may be very limited in its capabilities. I know it will all make sense once the bike is delivered along with the programming cable/software.


I really don't care about the limit itself - 750W on throttle is plenty. I'm just curious why it's a fixed number, rather than ramping the power with at least the wheel speed sensor; this is what would happen with cadence detection kicking in. I'd also expect improvement here as we get electronic shifting in the coming years, and perhaps a stronger ebike-specific IGH as ebikes gain further popularity.
 

Ebiker33

Well-Known Member
I know the purpose of the throttle restriction, but you're not understanding what I'm getting at. One may limit the throttle to 15A, but that alone doesn't protect the IGH. Through the cadence detection, you're then pushing 45A - much more input torque to the IGH. The IGH doesn't care if you're feeding it 45-50A (~2300W) from the throttle or the pedal-sensing; it will still have all that power hitting it. The "throttle limit" is just preventing people from holding the throttle for 10+ seconds to get up to speed in the incorrect gear. I understand that casual ebike-riders may treat their bikes as a single-speed.

I can easily put it in 14th gear and press down hard on the pedals from a stop. It shouldn't go anywhere, but somewhere the controller is detecting cadence and torque from the pedal. If I put the bike on a stand and just turn the pedals, is the thing going to try to give full power? I'd imagine so, and there's your high torque. It's still getting full power to the IGH - it just accelerates quicker due to lack of load.

I would think the throttle restriction only makes sense below a certain speed; otherwise the workaround once up to speed is to just ghost-pedal for full power.

I haven't seen anything shared about how the controller is programmed, what its curves look like, etc. The hard 750W limit makes me think the archon x1 may be very limited in its capabilities. I know it will all make sense once the bike is delivered along with the programming cable/software.


I really don't care about the limit itself - 750W on throttle is plenty. I'm just curious why it's a fixed number, rather than ramping the power with at least the wheel speed sensor; this is what would happen with cadence detection kicking in. I'd also expect improvement here as we get electronic shifting in the coming years, and perhaps a stronger ebike-specific IGH as ebikes gain further popularity.
Well no matter how hard you pedal the IGH is protected, that is not the case with the throttle, we spent many posts digging through all this months ago, suffice to say I agree with the 750W limitation.
Think pressure washer verses garden hose, to keep it simple.
 

BarnBoy

Well-Known Member
Region
USA
City
Pleasanton, CA
Hello to all, silly question, first post and proud holder of a WW order (late to the show!). @pushkar the last AMA was so informative, thank you for taking the time to do these! When is the next one scheduled?
 
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Acme

Well-Known Member
Re: throttle 750w-2300w. I have the ultra with archon X1 controller on a Frey CC which is full suspension. I can access the throttle at 750w, 1000w and 2300w depending on the assist level I am in. On trails I am almost always in 750w -1000w assist. I use the 2300w assist almost exclusively for paved roads. The trails with ruts and rocks you can picture the momentary load that might be applied to a the chain which is the week point on these bikes. The throttle which is not as gradual or smooth as assist is very difficult to use over 750W on trails. It will jump to full throttle so easily I am always worried about breaking a chain At 2300w. The pedal assist is far smoother. What I’m trying to say here is you can only put so much power through the chain without having it break. If you’re riding on uneven terrain the stresses can climb to breaking levels almost instantly so having all that power isn’t necessarily a good thing with the lack of control the throttle leaves you with.
If you have the echo assess levels site at 750 or 1000 in the throttle will be the same and the turbo set at 2000 or 2300 W than a throttle will be at that level. This allows you the choice of levels and can get you home without having to stop and put a new chain on if you even have a spare.
 

BarnBoy

Well-Known Member
Region
USA
City
Pleasanton, CA
Welcome! What did you go with? I’m eagerly awaiting a Helios myself.
Thanks @coldriderwi! I ponied up for what I hope to be @pushkar ’s first XL Hydra bloated with Kindernay and 26x4.8 Nextie. Now going to add a 29x? Nextie Spare wheel set. Looking to add lights and other goodies as they get presented in an AMA. Still not decided on carbon bar and cranks; I’m a really big guy and attracted to a >300lbs rated bike as I break stuff! Also hemming and hawing about a custom paint job....

GAAAA- too many choices!
 

reed scott

Well-Known Member
Hello to all, silly question, first post and proud holder of a WW order (late to the show!). @pushkar the last AMA was so I formative, thank you for taking the time to do these! When is the next one scheduled?
Hello BarnBoy. I've been noticing your posts the last few days. I can tell you are going back and reading up on Wattwagons and a lot of our contributions who have a stake in this deal. My compliments. It is refreshing to see a new 'convert' come in and do the work to become informed instead of dropping in out of nowhere and want everybody to bring them up to speed. Welcome. 👍
 

greeno

Active Member
Region
USA
City
San Diego
I gotta chime in. I know having the throttle restricted to 750w is for liability purposes but if you have half a clue on how to ride a bike you should instantly know if you were in the wrong gear when starting from a dead stop and if you still continue on trying to accelerate you kinda deserve what you get, IMO. I really only use my throttle in a tight situation say in a technical climb up through a rock garden when rotating the pedals could be 50/50 afair as far as being stopped dead in my tracks.
I am a BIG FAN of the Archon X1 controller upgrade I realistically use my throttle 2% of the time, the PAS programming is so good for my style of riding. I did adjust my throttle and torque settings to 100%.
My buddy just received an "Andy Kirby Vapour" bike which has the stock Bafang Ultra motor and controller so here pretty quick we will try to adjust his programming where we can but worst case is we send it out east to Pushkar and have it tuned up proper.
Funny when I was searching for a full suspension e-bike, main thing it had to have a throttle..... now not as much so. Don't get me wrong having 1500w instead of 350-500w was a deal breaker too.

Ah the joys of being retired.
 

Ebiker33

Well-Known Member
I gotta chime in. I know having the throttle restricted to 750w is for liability purposes but if you have half a clue on how to ride a bike you should instantly know if you were in the wrong gear when starting from a dead stop and if you still continue on trying to accelerate you kinda deserve what you get, IMO. I really only use my throttle in a tight situation say in a technical climb up through a rock garden when rotating the pedals could be 50/50 afair as far as being stopped dead in my tracks.
I am a BIG FAN of the Archon X1 controller upgrade I realistically use my throttle 2% of the time, the PAS programming is so good for my style of riding. I did adjust my throttle and torque settings to 100%.
My buddy just received an "Andy Kirby Vapour" bike which has the stock Bafang Ultra motor and controller so here pretty quick we will try to adjust his programming where we can but worst case is we send it out east to Pushkar and have it tuned up proper.
Funny when I was searching for a full suspension e-bike, main thing it had to have a throttle..... now not as much so. Don't get me wrong having 1500w instead of 350-500w was a deal breaker too.

Ah the joys of being retired.
So your saying the X1 is so good at giving assistance at the assigned PAS level, that a rider naturally uses the throttle less, because you almost don't need it ?
 

greeno

Active Member
Region
USA
City
San Diego
Bingo thats my opinion. Coming from a hot rod BBSHD from luna, I would take this motor hands down. One buddy has a biktrix juggernaut FS and another friend just got his AK Vapour. Different companies different programming. If I can climb off my ride long enough to fully check out theirs I will in the next couple of weeks and do a comparison
 

Acme

Well-Known Member
I would say you are at least half correct. It is a much better controller. i also seldom use my throttle. I had to tow my niece up a 2 mile fire road and at 750w setting I felt safe I would not break the chain and we would both be walking. yesterday I had to catchup to a friend who was a way better rider than the rest of us and used 2000w. I like having both settings available