New Bafang Crank-Drives

[kampua]

Anyone else has the same problem as experienced by Kepler and Melbourne? wondering how common is that problem.

 

[ebike11]

What are some of the higher speeds you guys reaching with this motor?

 

[teslanv]

What are some of the higher speeds you guys reaching with this motor?

My Gearing:
48T Chain Ring (Kit Standard)
11T High Gear at Rear
12S HK LiPo Battery, 50.4V HOC.
My top Speed is software limited to 31 MPH - and it seems that I can just barely get it to that speed. (90 RPM at Crank)

However ebike11's question brings up another question:

What is the fastest Crank RPM you are seeing at lower gears & speeds (And is Max Crank RPM a function of Voltage)?

If we can establish the maximum Crank RPM's, then we should be able to extrapolate the maximum possible speed of a given gear ratio.

I will try to do some testing on mine in the next few days.

 

[Rusty123]

What are some of the higher speeds you guys reaching with this motor?

My Gearing:
48T Chain Ring (Kit Standard)
11T High Gear at Rear
12S HK LiPo Battery, 50.4V HOC.
My top Speed is software limited to 31 MPH - and it seems that I can just barely get it to that speed. (90 RPM at Crank)

However ebike11's question brings up another question:

What is the fastest Crank RPM you are seeing at lower gears & speeds (And is Max Crank RPM a function of Voltage)?

If we can establish the maximum Crank RPM's, then we should be able to extrapolate the maximum possible speed of a given gear ratio.

I will try to do some testing on mine in the next few days.

Tesla,

I think the max speed you are seeing is a function of max crank rpm (although your mph limiter would kick in shortly after that). I've run mine through different gears while on a bike stand -- no significant wind or friction loss -- and the crank has a pretty definite max rpm. I didn't measure it, but I would guess its around 90 rpm or so. In fact, I've found that's it's not too hard to overrun the pedal assist, although at a cadence much higher than I prefer.

Not sure if max crank rpm is a function of voltage. I understand that on hub motors, higher voltage = higher speed, but I wouldn't be surprised if crank speed is controller limited on this unit.

 

[teslanv]

Rusty,

Good idea to test on the bench. If we can determine that the RPM's max at around 90 unloaded, then we can determine our theoretical max speed for any given gear ratio.

I whipped up an excel spreadsheet that will calculate speed based on gearing, Crank RPM and Wheel Size. - so It's easy to check RPM just based on the Bafang Head unit display's Speed reading.

PM me if you want a copy.

Here's a pic of my calculator.

 

[Kepler]

I will grab a copy if that if you dont mind.

With the fuel economy calc, it is a good idea to add a second calc that takes into account your battery costs and estimated cycles. As with the electrons used, the battery is in reality a consumable also. When you factor this in, economy against an ICE doesn't look quite so exciting. Still other major advantages to take into consideration with electric of course

 

[EVTodd]

I will grab a copy if that if you dont mind.

With the fuel economy calc, it is a good idea to add a second calc that takes into account your battery costs and estimated cycles. As with the electrons used, the battery is in reality a consumable also. When you factor this in, economy against an ICE doesn't look quite so exciting. Still other major advantages to take into consideration with electric of course

So true, and if you did the same calculations against a 80 mpg scooter it would be even less exciting. On the other hand, you have to figure in how much insurance, tags, etc, cost for the ice vehicle too.

 

[Warren]

teslanv,

"I whipped up an excel spreadsheet that will calculate speed based on gearing, Crank RPM and Wheel Size. - so It's easy to check RPM just based on the Bafang Head unit display's Speed reading."

You could just use the late, great Sheldon Brown's old calculator.

http://www.sheldonbrown.com/gears/

 

[teslanv]

Kepler,

Per your request - added the battery into the equation.

I wasn't sure about cycle lifespan of my Turnigy Hardcase packs, but it's user definable so you can adjust per real world results. - And really easy to plug in your own battery cost/voltage/capacity/lifespan. Not a bad way to compare battery types, as well, I suppose.

[edit] Added a sheet for the metric world - cause I know how you all hate converting for us Yankees.

 

[Melbourne]

I will grab a copy if that if you dont mind.

With the fuel economy calc, it is a good idea to add a second calc that takes into account your battery costs and estimated cycles. As with the electrons used, the battery is in reality a consumable also. When you factor this in, economy against an ICE doesn't look quite so exciting. Still other major advantages to take into consideration with electric of course

So true, and if you did the same calculations against a 80 mpg scooter it would be even less exciting. On the other hand, you have to figure in how much insurance, tags, etc, cost for the ice vehicle too.

lol... reminders me I need to get rid of my Car/Harley sportster/Jap bike... insurance/tag =~$3000/year and all sitting idle for a year thanks to my ebike. Might keep my Harley for fun as i spent ~$5000 modding 4 speed. Wat a waste of cash... Big Regrets considering I am going to lose my job due to the downturn in the car manuf industry in Oz.

 

[Kepler]

Kepler,

Per your request - added the battery into the equation.

I wasn't sure about cycle lifespan of my Turnigy Hardcase packs, but it's user definable so you can adjust per real world results. - And really easy to plug in your own battery cost/voltage/capacity/lifespan. Not a bad way to compare battery types, as well, I suppose.

[edit] Added a sheet for the metric world - cause I know how you all hate converting for us Yankees.

Nicely done. I like the way you even researched how much Gasoline and electricity cost us here. Good reason to ride ebikes.

I would suggest half the battery cycle to 250 for a more realistic life cycle of a LiPo. Also landed cost of 10ah 48V LiPo is closer to $250 AUD.

 

[teslanv]

BBS02 - 750W 48V bench test results on the unloaded Crank RPM test:

Battery Wattage @ Test: 50.8V

RPM: 126.7 at the crank.

With a 48T Chain Ring, 11T Rear Sprocket, and 26" Wheel, that's a 42.8 mph theoretical maximum speed (at no load, no wind resistance)

 

[Kepler]

Yep, that sounds about right. I hit 64kph (40mph)going down a hill that kind of neutralizes out other opposing forces. (bike hits about 35kph if just left to roll freely) Gearing is 48/11 on a 26" tire.

 

[m4s73r]

So the question now is does the rpm of the crank change under different amp load. I know most people are looking at this for mountain biking. Im wanting to use it for road touring on a tadpole trike. With a DuelDrive w/11-36 cassette i can turn that 48 into a 36/48/63. at 100 rpm and a 26" wheel thats a top speed of 45 mph in high and 7 mph in low.

 

[Geebee]

Link to Australian retailer BBS01 $500 250w $550 350w http://www.value-e-bikes.com.au/ConversionKits.htm
The sites a mess atm but I have come across it for years when googling and he has distributors in some other states, not Tas
Havent seen a reply to the email sent on the weekend but a phone call might get a quicker response.

And on a totally different note I found this on a French forum

http://cyclurba.fr/forum/278462/bbs01-montage-plateau-bafang.html?from=31&discussionID=13280&messageID=278462&rubriqueID=102&pageprec=

 

[m4s73r]

I read through some of that forum. Sounds like they have been using the 350 watt for the same thing that everyone wants the 750 for. There were several guys with double chain wheels that are manually moving the chain ring for lower or higher gears. I think this will work for me since im on a trike with a long chain and idler pulleys. go with a 38/60t. with the duel drive that should give me a 28,38,45,50,60,79 chain ring options for 21-189 GI.

 

[Geebee]

Fit a chain tube to the upper chain if not fitted and you can just reach forward whilst riding and shift.

 

[m4s73r]

At least at first. I dont think it would be difficult to get a front derailleur on there. Just not sure if one can move a chain from 38t to a 60t.

 

[rodgah]

Link to Australian retailer BBS01 $500 250w $550 350w http://www.value-e-bikes.com.au/ConversionKits.htm
The sites a mess atm but I have come across it for years when googling and he has distributors in some other states, not Tas
Havent seen a reply to the email sent on the weekend but a phone call might get a quicker response.

And on a totally different note I found this on a French forum

http://cyclurba.fr/forum/278462/bbs01-montage-plateau-bafang.html?from=31&discussionID=13280&messageID=278462&rubriqueID=102&pageprec=

HA! a local to me. I am gathering from his site he might not be the most internet trawling type of fella, might of never heard of ES either.

 

[jateureka]

I stumbled across product news of this switch that attaches to shift cable outer to detect inner cable movement and cut the throttle based on the shift.

http://www.bike-eu.com/Sales-Trends/Product-trends/2013/8/Revolution-in-Bottom-Bracket-Motors-1314760W/

Based on an intelligent gear sensor mounted on the shifting cable, it cuts off the motor drive when the rider activates gear shifting. It eliminates noisy derailleur shifting caused by chain over straining. This new technical solution was developed in the Czech republic and is called 'Gear sensor'. Even in combination with the front derailleur it allows smooth shifting if the e-bike is equipped with a double/triple chainwheel BB motor. The processors enable individual time setting and adjustment for micro-movement sensitivity of the inner cable, to avoid motor cut off caused by cable vibration.

Nice find. Will be interesting to see if it becomes available. At least for now we have a hack that does the same thing. I think this mod was one of the best things I have done with the middrive. Probably not so important on the 250W versions but a great asset on the 750W drive.

More info on that gear sensor here
http://gearsensor.com/

 

[m4s73r]

Looks like another version of the Bafang is coming from a company called Greentrans

http://www.bike-eu.com/Sales-Trends/Product-trends/2014/2/GreenTrans-Presents-Mid-Motor-Power-Kit-1471962W/

 

[jateureka]

I think that Greentrans is more for OEM as it looks like you need a custom frame to mount it, so more like Bosch than Bafang.

 

[CdnE90]

So the question now is does the rpm of the crank change under different amp load. I know most people are looking at this for mountain biking. Im wanting to use it for road touring on a tadpole trike. With a DuelDrive w/11-36 cassette i can turn that 48 into a 36/48/63. at 100 rpm and a 26" wheel thats a top speed of 45 mph in high and 7 mph in low.

Here's a graph for the BBS02 48V I "borrowed" from the TNA webpage http://www.tnabattery-ebike.com/?Bafang-BBS02-crank-drive-motor-p197.html. Not sure if this is for the 750W version or not, as it's Max Power In (Max Pin) is listed as 800W. However, it does show that it's max RPM is 112 (unloaded). Interesting that max efficiency is about 100 RPM, which is faster than most people natural cadence.

As some people were asking, the webpage also shows the 36V version (500W). It's no-load RPM is listed as 82RPM which seems to validate what people have said, which is that the 36V has a significantly lower top speed.

 

[teslanv]

Interesting that the TNA Website also lists in their index that the Max Amps on the BBS02 is only 15. - Perhaps this is the 500W Version of the drive, not the 750W, which is rated for 25A.

 

[Warren]

CdnE90,

"Here's a graph for the BBS02 48V I "borrowed" from the TNA webpage"

Thanks for that link. So, not surprisingly, it has max efficiency at about 80% of no-load rpm, and max torque at about 50% of no-load rpm...just like every other electric motor.

"Interesting that max efficiency is about 100 RPM, which is faster than most people natural cadence."

I suspect they figure most people will not be riding for efficiency, but more like scooter riding. So down around 60 rpm, at max torque, is about all most no cyclists are going to pedal anyway.