BBS02 vs BBSHD - how much can you alter programming also

[kiltedcelt]

So I already have the BBSHD and I know of it's advantages in heat dissipation and torque over the BBS02, however I'm looking for a lighter weight motor. Since I can't afford a Cyc motor (or at least not in the budget right now), I had been looking at TSDZ2B for a lighter motor with bonus torque sensing for a much more seamless assist feeling over the PAS on the Bafang mid-drives. Three things I want from an e-assist are 1. assist to help on the really windy days and also shave a few minutes off the 22 mile round trip commute 2. As much range as I can possible wring out of my EM3ev 52v 17Ah Super Shark battery. 3. To be able to use the assist but pedal and still get exercise. This last one is kind of aggravating with the BBSHD as I currently find that I often don't get quite enough assist (at say level 2 or 3 out of 9), to be really worth much, but then going to level 4 or 5 with the assist means I'm essentially soft-pedaling and I'm hardly getting any exercise anymore.

So, as regards getting more range - obviously less/lower level of assist translates to greater range - I've seen this in a practical manner as greatly reduced range from the days where I've ridden in level 5 or 6 due to massive headwinds. Would a BBS02 by virtue of being a lower wattage motor (750W), potentially allow me to eke a bit more range out of the battery or does that not really matter and the BBSHD is always going to win out by being better in terms of torque and heat dissipation? Do either of those even figure into a discussion about range? Can either motor be configured with the programming cable to make the level of assist be a bit more granular, like maybe make each level of assist be far more gradual? I never use throttle and I only want assist as the result of my pedaling and I'm more wanting the assist for the previous reasons mentioned about battling occasional headwinds and shortening the commute some, but I also want the assist to be able to help extend the range of rides like allowing me to ride my trike on camping trips of up to 60 to maybe even 80 miles one way, with recharging at destination of course.

I've been considering the TSDZ2B motor mainly because I know stock Bosch torque sensing mid-drives can get some pretty amazing mileage numbers from batteries half the size of my current 52v 17Ah battery. I figured that a torque sensing TSDZ2 motor might be able to yield similarly high range numbers but I'm balking a little at the complexity of the Open Source Firmware programming/modification, and also the somewhat delicate mechanical nature of the TSDZ2 motor versus BBSxx motors. It is a lighter motor, but the overall weight might be less of an issue if the TSDZ2 isn't as mechanically reliable. Are the BBSxx motors able to be configured with the programming cable to create a motor that would operate more along the lines of what I currently am looking for - basically getting more range, more exercise from pedaling, and maybe figuring out some way to make them operate a bit more "smoothly?" If my biggest reason for ditching the BBSHD is the weight, is the BBS02 really any better since it's only about a pound lighter? TSDZ2 is lighter of course and torque sensing would feel better in terms of the assist but I think I'm just balking at the mechanical issues I've heard of and also not really wanting to have to tinker a bunch with the OSF all the time not to mention worrying about inadvertently bricking the motor and my battery. The more I weigh all these factors, the more everything seems to get more muddied.

 

[Chalo]

TSDZ2 is unreliable, underengineered, and junky. So that should be a factor in your decision.

 

[silenec]

Just keep the BBSHD and get a programming cable. Stock programming is garbage but you can adjust it exactly how you like and then it's very good.

 

[jonsully]

Yeah I'll contribute to this too — I know exactly what you mean about the BBSHD not being pedaler-friendly. I wrote a programming that's made to combat this exact problem. It allows those who desire to ride with the motor — true pedal assist — not just be ghost-pedaling as the motor zips along without a care about the rider. As an added benefit, this programming also tends to use less battery power and thus extends range. I've had a lot of people use it with great joy

Sully's BBSHD Programming (for people that like pedaling)

How to program a Bafang BBSHD to ride WITH the motor!

jonsully.net

 

[ddm5]

Yeah I'll contribute to this too — I know exactly what you mean about the BBSHD not being pedaler-friendly. I wrote a programming that's made to combat this exact problem. It allows those who desire to ride with the motor — true pedal assist — not just be ghost-pedaling as the motor zips along without a care about the rider. As an added benefit, this programming also tends to use less battery power and thus extends range. I've had a lot of people use it with great joy

Sully's BBSHD Programming (for people that like pedaling)

How to program a Bafang BBSHD to ride WITH the motor!

jonsully.net

Thanks for this. I found this page last week when waiting for my BBSHD kit to arrive and then couldn't find it again when I wanted to program it to reduce ghost pedalling.

My only concern with this method of controlling the assist power is that everyone says the motors work best at high rpm, lots of power at low rpm is bad for the motor?

So by using this method of limiting, your effectively ensuring the motor never reaches more than 50% of it's maximum RPM, while still asking for 77% of the power?

Or am I misunderstanding?

 

[jonsully]

No, this is a great point, a good concern, and a well-eyed question!

All brushless DC motors reach their highest point of efficiency (least heat created per watt generated) in the upper reaches of their maximum RPM — usually above 80%. That's definitely true. But how much wattage you're asking for in any given moment plays a factor there too. If the motor is running at 50% RPM it's less efficient than at 90% RPM but if you're only asking for 15% of its maximum amperage, the efficiency difference between the two RPMs will be negligible. Now, that said, if you're asking for 100% amperage all the time but limiting RPM to 50%, you'll experience a notable difference in observed efficiency (putting your hand on the motor and noting how hot it is) compared to 100% amperage at 100% RPM. The key factor at play with this tuning is the amount of time we're asking for high amperage at 50% RPM. It's not much.

Because this tuning seeks to "get you to happy cadence then just help you stay there" what we're actually talking about is a small peak of amperage (max of 23A with 77% current limiter) at little/no RPM when you first start moving the bike but it likely only lasts 2-3 seconds before falling down to the "at spinning speed" amperage (on flat ground with my rig @ 18mph that tends to be 4-6 amps; 13-20% of max amperage). Efficiency losses from gated RPM really don't matter at 4-6 amps of constant current.

Then, of course, if you shift up to the next gear, you get another amperage peak for probably 2-3 seconds (again, max of 23A with 77% current limiter) as the motor works to get your cadence back up to the happy range.

So the question is then, is running up to 23A of current through the motor when it's between (let's say) 45-60% of its maximum RPM inefficient? Or, also importantly, is it bad for it? And my answer there is that no, running 23A of current through the motor for a few seconds at a starting RPM of 45% isn't going to hurt the motor. I've seen lots of folks who routinely push 100% amperage on a fully charged 58.8V battery through the motor when the bike is at a dead-stop (via throttle). I certainly don't advise that, but the BBSHD is a tank. Even at 70rpm crank cadence (roughly 45% of the max motor RPM), that's enough spinning to keep the motor from having torque problems in its step-down gearing. Will it generate a little more heat than other ways of operating the motor? Sure, but then, there aren't any other ways of operating the motor such that you can pedal with it. Since we can't change the step-down gear ratios inside the motor, we're stuck with the reality that to pedal at human-cadences with the motor, we must accept that the motor will run at a fraction of its peak RPM (and thus generate just a bit more heat).

But then, remember too that the folks who ride BBSHD MTB's and throttle-only all day long are pushing a LOT more heat through their motors than this programming ever will. Sure, they're at a higher point of efficiency within the motor, but since they're pushing high amperage for many, many minutes at a time, that high efficiency heat yield still adds up to an overall hot motor! My programming is one I'd generally consider pretty gentle on the motor, even if you left Current% at 100% and just had the Speed% limiter. Now, just out of an abundance of preference for longevity, I limit my Current% to 77%, but I wouldn't bat an eye at someone that doesn't. I don't know at all whether my limit of 77% will actually yield a longer motor lifetime for me compared to 100%

Hope that helps and answers some questions! Thanks for prompting me to finally write all this out!

---

Ultimately you've stumbled upon the only real change I wish was possible for the BBSHD — that the step-down internal gearing was an even higher ratio such that human cadences would == efficient motor RPMs! The fact that the most efficient motor band (90%+) results in cadences above 120rpm is unfortunate. The thing is an absolute tank and a beast, but I wish it was geared a little heavier!

 

[jonsully]

Oh and for what it's worth, to the question of range (one of your original major questions), I have a 52V 21Ah battery on my giant cargo bike (26x2.4 tires), I ride extremely upright (like a sail in the wind), my total rig weight is 350-400lbs at any given time, and my typical riding speed is 17-18mph using my programming (usually targeting cadence 85-90).

With all of those factors at play, that battery gives me about 100 miles on a full charge. Programming, road speed, and aero position are the three biggest factors at play.

 

[richj8990]

No, this is a great point, a good concern, and a well-eyed question!

All brushless DC motors reach their highest point of efficiency (least heat created per watt generated) in the upper reaches of their maximum RPM — usually above 80%. That's definitely true.

One of the problems is that neither starting DC output or final gear reduced rpm show on most display screens. So you have to guess either by gear or by if you can hear the sound of the motor. I think this overheating thing is a bit overblown for most mid-drive motors unless someone is trying to blast up a big incline in one of the top gears. There are many dudes in my area with tiny 250W rated mid-drives that are trying to climb as fast as they can up 300 to 1000 foot hills, and most of them don't blow the motor. Some do, most don't.

I've run a lot of calculations lately through the Grin motor simulator (that is far from perfect) but for a 10% incline I basically came up with: don't exceed 1.3x chainring to cassette cog ratio. In other words if you have a 42T chainring, then don't shift up past around 32T on the back. I've noticed that most of the BSSxx people are running around a 1.0x ratio for the granny (largest/lowest gear), so often 42T front ring / 42T largest cassette cog, or 40T if they are doing 8 speed. So if the cassette is 8 speed, and it's something like 11-13-15-18-23-28-34-40, then on a 10% incline they should not go past cogs 1 or 2 (40 or 34). If they have a smaller chainring like 34T, then they could do 28T (3rd gear) but probably not 23T (4th gear).

If it's a 5% incline, then I didn't run the calculations but I'm assuming it's halfway from 1.3x to the final top gear ratio if whatever that is, maybe 3.8x if it's 42 front 11 rear. So it would be about 2.5x, which for a 42T chainring would be 17T. So they would be OK with 18T (5th gear) but maybe not with 15T (6th gear). Level surface of course they can use all gears.

 

[ddm5]

T

No, this is a great point, a good concern, and a well-eyed question!

All brushless DC motors reach their highest point of efficiency (least heat created per watt generated) in the upper reaches of their maximum RPM — usually above 80%. That's definitely true. But how much wattage you're asking for in any given moment plays a factor there too. If the motor is running at 50% RPM it's less efficient than at 90% RPM but if you're only asking for 15% of its maximum amperage, the efficiency difference between the two RPMs will be negligible. Now, that said, if you're asking for 100% amperage all the time but limiting RPM to 50%, you'll experience a notable difference in observed efficiency (putting your hand on the motor and noting how hot it is) compared to 100% amperage at 100% RPM. The key factor at play with this tuning is the amount of time we're asking for high amperage at 50% RPM. It's not much.

Because this tuning seeks to "get you to happy cadence then just help you stay there" what we're actually talking about is a small peak of amperage (max of 23A with 77% current limiter) at little/no RPM when you first start moving the bike but it likely only lasts 2-3 seconds before falling down to the "at spinning speed" amperage (on flat ground with my rig @ 18mph that tends to be 4-6 amps; 13-20% of max amperage). Efficiency losses from gated RPM really don't matter at 4-6 amps of constant current.

Then, of course, if you shift up to the next gear, you get another amperage peak for probably 2-3 seconds (again, max of 23A with 77% current limiter) as the motor works to get your cadence back up to the happy range.

So the question is then, is running up to 23A of current through the motor when it's between (let's say) 45-60% of its maximum RPM inefficient? Or, also importantly, is it bad for it? And my answer there is that no, running 23A of current through the motor for a few seconds at a starting RPM of 45% isn't going to hurt the motor. I've seen lots of folks who routinely push 100% amperage on a fully charged 58.8V battery through the motor when the bike is at a dead-stop (via throttle). I certainly don't advise that, but the BBSHD is a tank. Even at 70rpm crank cadence (roughly 45% of the max motor RPM), that's enough spinning to keep the motor from having torque problems in its step-down gearing. Will it generate a little more heat than other ways of operating the motor? Sure, but then, there aren't any other ways of operating the motor such that you can pedal with it. Since we can't change the step-down gear ratios inside the motor, we're stuck with the reality that to pedal at human-cadences with the motor, we must accept that the motor will run at a fraction of its peak RPM (and thus generate just a bit more heat).

But then, remember too that the folks who ride BBSHD MTB's and throttle-only all day long are pushing a LOT more heat through their motors than this programming ever will. Sure, they're at a higher point of efficiency within the motor, but since they're pushing high amperage for many, many minutes at a time, that high efficiency heat yield still adds up to an overall hot motor! My programming is one I'd generally consider pretty gentle on the motor, even if you left Current% at 100% and just had the Speed% limiter. Now, just out of an abundance of preference for longevity, I limit my Current% to 77%, but I wouldn't bat an eye at someone that doesn't. I don't know at all whether my limit of 77% will actually yield a longer motor lifetime for me compared to 100%

Hope that helps and answers some questions! Thanks for prompting me to finally write all this out!

---

Ultimately you've stumbled upon the only real change I wish was possible for the BBSHD — that the step-down internal gearing was an even higher ratio such that human cadences would == efficient motor RPMs! The fact that the most efficient motor band (90%+) results in cadences above 120rpm is unfortunate. The thing is an absolute tank and a beast, but I wish it was geared a little heavier!

Thank you for the detailed explanation, I flashed the OSF for the BBSHD, so my parameters for config are slightly different now...

I set a profile with 100% max current on all PAS levels using 48-60% max cadence to try and find my happy level. Seems my happy cadence is roughly the same as yours, however I felt like the bike was holding back a lot of power due to this, and I was having to pedal harder a lot more, (of course this is obvious if you think about it, as free range/energy can't come from thin air - like you have said),

I will need to experiment more with it. I also have a very small shitty display with no watts/amps (or even voltage from battery, just 5 bars), and hardcoded 5 PAS levels, so it's difficult to monitor in real time to see what the motor is doing.

 

[jonsully]

One of the problems is that neither starting DC output or final gear reduced rpm show on most display screens.

I agree with this for sure. I've asked the EggRider devs if they can add cadence to the screen — but in the meantime I do often ride with my Garmin running and cadence showing there (cheap, external cadence sensor on crank)

Seems my happy cadence is roughly the same as yours, however I felt like the bike was holding back a lot of power due to this, and I was having to pedal harder a lot more, (of course this is obvious if you think about it, as free range/energy can't come from thin air - like you have said),

It's tough to explain over text but while I spin with the motor (maintain a mechanical connection) I often don't put much oomph into the drivetrain from my thighs at all. Spinning, but with zero actual watts from my muscles. You should hopefully be able to experience this too — you shouldn't have to pedal harder, per se... but it is also true that free energy isn't possible. You should be able to find the balance somewhere in the RPM range!

I also have a very small shitty display with no watts/amps (or even voltage from battery, just 5 bars), and hardcoded 5 PAS levels, so it's difficult to monitor in real time to see what the motor is doing.

Which display is it? I swore most of them had a hidden menu for switching from 5 PAS levels to 9!

 

[ddm5]

It's tough to explain over text but while I spin with the motor (maintain a mechanical connection) I often don't put much oomph into the drivetrain from my thighs at all. Spinning, but with zero actual watts from my muscles. You should hopefully be able to experience this too — you shouldn't have to pedal harder, per se... but it is also true that free energy isn't possible. You should be able to find the balance somewhere in the RPM range!



Which display is it? I swore most of them had a hidden menu for switching from 5 PAS levels to 9!

I understand exactly what you mean, this is my first ever ebike, and first ANY bike in a long time, I knew absolutely nothing about them 2 weeks ago, but learning everything I can. I went from wanting a cheap rear hub drive to try out to ending up with a BBSHD while learning the ins and outs...

I've done 100+ miles on this kit over the past 3/4 days and have definitely felt that happy zone a few times, where I am basically 'just' not ghost pedalling (best way I can describe it?), feels like your are giving pretty much zero effort / power but still pedalling and connected to the drivetrain.

I think it's called the BN136, the display I wanted was out of stock with the kit, so I ordered with no display, the kit ended up arriving much sooner than expected (before I could get the display I wanted elsewhere), so I jumped on Amazon and bought the cheapest Bafang UART compatible display I could find (serves me right tbf) so I could get going ASAP.

I'm not sure if it's the latest BBSHD's or this display (or a combo of both), but I'm also unable to change the wheel size in the display too, I can get into the 'Menu' but to change rim size there is another menu, which I can't get to activate at all.

 

[jonsully]

I've done 100+ miles on this kit over the past 3/4 days and have definitely felt that happy zone a few times, where I am basically 'just' not ghost pedalling (best way I can describe it?), feels like your are giving pretty much zero effort / power but still pedalling and connected to the drivetrain.

Yeah, pretty much! Nice

Understood on the display front. Yeah, I've never even seen that one and technically anybody can build a UART compatible display but YMMV on how configurable it is. I believe wheel size is totally a concern of the display alone — I believe the display only gets data from the controller about the speed sensor's pings and the display has to do the math itself for how much road speed that equals. Might want to grab a better display, honestly! The 500C is a great option if you prefer the smaller screens (as I do)

 

[ddm5]

Yeah, pretty much! Nice

Understood on the display front. Yeah, I've never even seen that one and technically anybody can build a UART compatible display but YMMV on how configurable it is. I believe wheel size is totally a concern of the display alone — I believe the display only gets data from the controller about the speed sensor's pings and the display has to do the math itself for how much road speed that equals. Might want to grab a better display, honestly! The 500C is a great option if you prefer the smaller screens (as I do)

The 500C was my initial choice, but saw people saying it's not great in direct sunlight, and them having to try and cover the screen to see the info.

I do like the smaller, more discreet displays.... but I think I'd also like one with separate 'Up' and 'Down' buttons that are reachable without taking hand off grip.

My plan is still to get a display, I just haven't decided on what one yet.. so this will have to do for now.

 

[jonsully]

I had the 500C and didn't ever experience issues seeing it, but as always, YMMV!

 

[uhmwpolyethylene]

I'm so torn on the BBSHD vs BBS02. I demoed the BBSHD and its about the right power at 240lb i would need to get uphill maybe a bit too much, I could go with the 02. especially dropping 3.5 lb on that lighter motor. But so many people talking about 02 reliability issues, but not just that, the legality in USA. I want to do food delivery in high profile areas like San Francisco, and i suspect even sanding off the engraved "1000w" on the bbshd wouldn't work as now especially with AI image search you could easily tell its the 1000w bafang not the 750w BBS02. Such a tough call. What can be done to improve the bbs02, are replacing MOSFET ahead of time and increased greasing supposed to help? Putting heat sinks outside the 02? The CYC Photon makes me nervous, but it is advertised as 750w. was waiting on the bikee lightest but no one has got it working yet. I'm looking to do a really high end legal build, maybe even using a S-Works MTB base at 22lb. (I heard mid drives can knock around in carbon, is that true? Some people said Alu and titanium are best, and steel creaks too much)

I feel like the 02 would be great for the s-works (maybe 6000 used, 23 lb) and the bbshd for the pole evolink (36-37 lb, 2500 used) . I had looked at road bikes and lightweight hybrids lacking suspension forks too.

 

[Chalo]

I'm so torn on the BBSHD vs BBS02. I demoed the BBSHD and its about the right power at 240lb i would need to get uphill maybe a bit too much, I could go with the 02.

BBS02 was my own experiment with through-the-gears mid drive. I used 44t and 42t chainrings with 14-34 or 16-40 7-speed cassette (on 9 speed spacing). 700x35 rear wheel. Later I switched to 26x1.5" wheel with a NuVinci N171 hub. In both cases it could climb everything in my area, and speed to 30mph on a maximum electrical power of about 1300W. It trashed cassettes and chains like that's what it was for. Trading smaller wheels for larger chainring would probably make it a lot less destructive.

(I heard mid drives can knock around in carbon, is that true? Some people said Alu and titanium are best, and steel creaks too much)

That's nonsense. I've seen them work loose on both steel and aluminum frames. They aren't any more likely to creak than pedal cranks. And as for Ti, why? Why use a motor that weighs 4X what your frame does? It kind of erases the subtle, possibly-worth-it-probably-not benefit of an expensive lightweight frame. E-bikes aren't pedal-only bikes, and they don't need to be very light to be their best. Heck, pedal bikes don't need that either, it's just a feature to sell to people with more money than understanding.

Carbon-resin frames usually have an aluminum insert for the bottom bracket shell. If the mid drive works loose, though, it would have an easier time doing structural damage to a plastic frame than to a metal one.

View attachment 341108View attachment 341109
I feel like the 02 would be great for the s-works (maybe 6000 used, 23 lb) and the bbshd for the pole evolink (36-37 lb, 2500 used) . I had looked at road bikes and lightweight hybrids lacking suspension forks too.

I think you should make up your mind whether you're looking for a folder or a real bike, and whether you're looking for a lightweight bike or a whiz-bang wanktastic suspension bike. You do have to choose, or you are likely to wind up with the worst qualities of everything.

 

[uhmwpolyethylene]

BBSHD related question, should I go with the bbs02 legality wise? I feel like even if I remove the engraving any AI image search or eyeballing might tell it's not the 750w max nominal legal bbs02. But people seem to complain about 02 a lot more, even if you can put heat sinks outside. I demoed the HD recently and feel like I could get away with 1300w vs 1700w HD at 52v. It's such a tough call and the bikee lightest and cyc photon seem dead in the water. If you could describe reliability in percentages , 02 vs HD, where would you place them. And is there anything else nominally 750 but peaks higher besides tongsheng and photon that's reliable, maybe not? Would heat sinks help the 02?
Possibility of re engraving