8fun crank drive kit

[eHomer]

I've carefully re-read all of this thread, (and the equally long one on ES).

The Bafang crank drive interests me for a future project, so I'd like to check out some of the notes I made about all the very useful discussions about it so far.

I see it's available via BMS now, (my most reliable Chinese source so far), in 3 different versions:

Central Motor

250W BBS01 @ $369 in 36v only
350W BBS01 @ $369 in 36v or 48v
500W BBS02 @ $399 in 36v or 48v

They don't list the 750w model, has it been discontinued or re-rated ?

Is the 500w a downgraded 750 or upgraded 350 ?

I understand the BBS02 designation was for "coaster brake", and Dave mentioned that was probably to allow back pedaling of the crank to operate the brake ? Is that the only difference ?

It was mentioned that all of the built-in controllers are sine wave, is that definite ?

I've taken in the comments about the pedal speed PAS making gear changing tricky, though Geebee's idea about blipping the brake cutouts may make that less of a problem, to a degree.

I do like the simplicity and neatness of fitting via the standard 68mm bottom bracket, and having the weight there.

I take the points about the motor being physically smaller, so less torquey, though surely the meaty looking primary bevel gearing has the same effect as a hub motor's planetary gears, bringing the torque up ?


Someone mentioned the difference between upping the voltage on crank drives and hub drives though. Is the primary gear ratio different for 36 and 48 volts use ? Otherwise, isn't the powered cadence going to be 33% faster for the 48v, compared to the 36v ?

The extra information available on the control panel looks handy.


Bearing in mind the general feeling shown that the 250 is underpowered compared to the same basic wattage equivalent hub motor, how does the 500W 36v version sound to people on here ?

Would a 36v 10ah Lithium Ion pack have enough constant discharge amps to run it ?

 

[Deleted member 4366]

At the Shanghai show, they had a 250w 36v one, and a 48v "750w" one.The "750w" one had a bit more power than the 250w one, but not a lot more. The different versions have the voltage and current stamped on the casing. i think I've seen 36V 15a, 36v 18a, 48v 18Aand 48v 25A. The one I tried had a 48v bottle battery, so I guess 48v 18A. I think it was a prototype, so might've even been 15A. The cadence felt OK - not that I thought about it or felt ant difference to the 36v one. They told me that the 48v one had different windings, so they've probably wound it for the sane speed.

If you've read ES, you'll know that there's lots of different software versions on each physical version, so you need to be careful what you're actually going to get. On some, you get no throttle.Others have strange throttle response.

Don't forget that the torque sensor version is imminent, but I wouldn't hold your breath on getting nice power algorithms, although we can always hope.

I'm still firmly of the opinion that hub-drives are best for commuting and touring. They're much more relaxing and have better power profiles. Crank-drives are better if you're a sporting cyclist. I haven't found any significant difference in efficiency either.

 

[eHomer]

When I first started tinkering with electric bikes I always thought that a crank drive motor using the bikes wide gear train was always going to be the most versatile and efficient solution.

I think maybe I'm still biasing myself with that thought, plus really liking the look of these new neat ones in the BB with no extra chains or idlers and cogs.

As you say though, a 350w geared hub motor is very rideable, and you keep all 27 gears, instead of dropping down to 9.

 

[trex]

I think crank drive is much more efficient than hub drive on smaller motors.
If you have a 500W hub motor, both systems can do 20-25mph, the advantage of crank drive disappears.
At 750W, a crank drive will have to run at 100+ RPM, not many can pedal that fast, a hub motor is definitively more comfortable to ride. At 1000W+, direct drive may be best.
Therefore, it does not make much sense to buy a 750W 8-Fun mid motor.

 

[wurly]

I am most likely going to buy a crank drive set up very soon.

I have built a Headway 36V 10AH pack which should be able to supply a constant 30A (or more) in preparation, but...my head is spinning as to which one

Bearing in mind i don't have a suitable bike yet, I'm after a fun hillclimber bike so top speed isn't a priority, i like cadence to be rather slow, so can anyone tell me, do you get much of a speed change from 36V to 48V like hubmotors?

I really like the idea of a gng2 kit. I realise there is a few fabricating issues with them, for me that isn't to much of a problem, then there is the Bafang crank drive. One thing i am not very keen on, is the integrated controller. It's a far neater assembly and from what i gather a very usable system, but if there is a controller/display problem you have a non functioning set up. I guess with gng2 it's a simpler system less refined but easier to maintain????

I wish someone could make my mind up because i can't at the moment.
Price wise, they all seem to be around the same with shipping, give or take £30-£40.
So i would a appreciate a quick summary of both set ups please......
(as i said, my head is spinning)

 

[Deleted member 4366]

The GNG Gen 2 is relatively noisy and agricultural. the Bafang is smooth and quiet.

 

[wurly]

Tongue in cheek....
Noisy agricultural = tough forgiving?
Smooth quiet = refined delicate?

Is there any thing that you don't like about the Bafang drives Dave? do you think they are the best value compared to the Gng Gen2.

 

[jackhandy]

The GNG Gen 2 is relatively noisy and agricultural. the Bafang is smooth and quiet.

I've always understood the GNGs are noisy because they have steel gears & this makes them pretty tough.

They are certainly a bit whiney, but that doesn't seem to matter too much when you're enjoying yourself offroad.

I wouldn't want to use mine more than necessary on the road, but that's as much due to the fact that it's a bouncer & the lack of PAS as about the dearth of finesse.

 

[Deleted member 4366]

The Bafang is a proper refined product. I expect we'll see a lot of OEM bikes with them next season. I don't think there's any comparison really. I think that you've already summed up the advantages of each system. The GNG definitely works OK and it's easy to install, but you have to keep on top of primary chain adjustments and lubrication to keep it running smoothly. As you've figured out, you can use any controller, display, PAS or throttle arrangement that you want. The Bafang is what it is. You stick it in,and then start using it, hoping that you haven't got a PAS-only one. there's nothing to stop you using an external controller because the motor connections are accessible. If I were to buy one now,it would be the Bafang all the way. No contest. I think the 500w will hit the sweet-spot. The 250W one is too weak, and too much power is not good for your gears and gear-changes, so I can imagine the 750W one not being as comfortable.

 

[eHomer]

.......hoping that you haven't got a PAS-only one......

On the BMS site, they show their 500w BBS02 kit contents with a throttle and their connecting loom has connections for one, together with the panel and brake levers.

Or do you mean that the throttle may only be PAS start, and not independent at startup ?


500W BBS02 Bafang Central Motor - BMSBATTERY

 

[Deleted member 4366]

Apparently,all options are possible depending how the software has been programmed. I'm only going by what i read on ES. It''s certainly possible to have an independent throttle, so you could check with BMSB if their throttle works independently - if you can trust their answers!

 

[eHomer]

I've emailed BMS to see if they will remove the software speed restriction and confirm that throttle works independently.


As you say, there are some worrying posts on Endless Sphere on this motor.

The guy who had two of them, and neither works via the throttle at all, and the only option they've given him is to return them at his cost, even though the admit it was their programming, ( very poor service, not BMS though).

The other chap who had a very localised winding melt, clearly a manufacturing defect, and he got no offer of a replacement either.

A few weeks back, someone on there sounded very optimistic about being able to reverse engineer the software and create something to program it, but that seems to have fizzled out too.

£250 with the shipping, and then maybe another £40 customs is a big gamble I suppose...

 

[Deleted member 4366]

I've emailed BMS to see if they will remove the software speed restriction and confirm that throttle works independently.

I'd be surprised if they know anything about software. They seemed to never have figured out the code numbers on BPMs after three years and countless requests. you wouldv'e thought that after the third person asked them, they would've looked at a motor to see what it is.

If you worded you question "Does it work with throttle no pedalling", you might get a more sensible response.

 

[eHomer]

You know me Dave, do I ever use one word when ten will do ?

I think I also asked something like "does the throttle work from startup, without any PAS rotation?"

It still appeals to me for trying out if they can confirm independent throttle.

ES seem to have sorted out all the workarounds for the PAS delay when changing gear and fooling the speed limiter with wheel size, though it does then make the speedo inaccurate.

I liked the simple solution that one person had with two sensor magnets at 180 degree spacing on the wheel, and swiveling one round for unlimited !

 

[Deleted member 4366]

I posted this in another thread, but if you didn't see it, look here:
New Bafang BBS02 750W mid drive for electric bicycles | ELECTRICBIKE.COM

 

[eHomer]

Yes, it was a really good review from that chap on the other forum.

The photos did the damage for me, (getting me hooked on it).

I've discovered a show stopper for my target bike though, my Giant Trance.

The bottom bracket is recessed by the swing arm pivots on both sides.

I could fit it on my Dahon folder though..... Damn....

 

[amigafan2003]

I've got a 48v500w unit coming that I'm going to run with my 15s (62.25v off charger) lipo pack.

It's going on this:-

I'll report back here with my experiences.

 

[eHomer]

The way the bottom bracket looks extended down from the frame makes it look as though it was designed with that mid drive in mind.

No problem with swinging arm protrusions and the motor should be able to swing right up out of the way, hardly altering the ground clearance at all.

 

[wurly]

I've got a 48v500w unit coming that I'm going to run with my 15s (62.25v off charger) lipo pack.

It's going on this:-

I'll report back here with my experiences.

Please do, i'm interested to see if the controller will be ok at 62.25V. Are you planning on using a throttle? as well as pedal sensors?


Is that your normal seat height? crikey! you must have long legs.

 

[eHomer]

...Is that your normal seat height? crikey! you must have long legs.

Better keep leaning well forward too....