Bafang BBS01 250w help

[NotWellInformed]

Hi there,

I installed my Bafang 250 BBS01 kit on the weekend, it's fun but I'm a little disappointed in the performance. I think I've diagnosed the issues, but was hoping for some guidance just in case I'm wrong.
I often feel like I'm working too hard to try and get it moving, almost like I'm pedalling against the resistance of the motor. I do a fair bit of cycling anyway so maybe I'm expecting too much from a 250w motor. The display seems to read that I'm using less that 118w for the majority of the time. This was particularly noticeable when going up a short, steep hill yesterday. I was having to work so hard, but just felt a lot of resistance when pedalling. I wasn't planning to use the throttle originally but this morning I put it on and and when I use it I do get the performance I was expecting when pedalling with it. It was reading an output of 350-500w.

So from the things I've read on here I think I need to:

Get a bigger chainring so I can put my pedalling to more use. It only came with a 44t chainring.

Get the cable to program the controller and change the PAS settings.

Any help is greatly appreciated.

 

[Mr Ted]

Here's the geeky answer based on some assumptions! I can't find the exact figure but the maximum torque of your drive is probably around 40Nm, in order for the motor to produce 250W of useful power the cranks would need to be turning at 60rpm . Below this speed the controller probably operates in constant current mode to hold the torque at the same level, if it didn't do this then the torque would rise as the speed dropped which would make for rather brisk starts. Using our meat motor we tend to cycle at constant (ish) torque and use the gears to maintain a constant power output.

Depending on the characteristics of the motor/gearbox the peak power will start to drop at some crank speed above 60rpm.

So you need to look at your gearing based around having maximum assist at cadences of 60 and above, without seeing actual measurements we can only guess at what cadence the power output drops. (The Bosch CX produces maximum power at 85rpm and is about 10% down at 70rpm and 100rpm)

If the maximum torque of 40Nm is held constant below 60rpm then at half the cadence you will get just half the power, 30rpm=125W

Hope this helps!!

 

[Woosh]

I installed my Bafang 250 BBS01 kit on the weekend, it's fun but I'm a little disappointed in the performance. I think I've diagnosed the issues, but was hoping for some guidance just in case I'm wrong.

does your kit work properly on throttle without pedaling?
if it does, then next, check that the cranks can rotate backward freely.

 

[peter.c]

you need to set it up with the lead and a laptop out of the box the settings are
the keep current will make the biggest difference some are set very low at 40%

 

[Nealh]

My one was set for 20% KC but was great for range.

I should have no such issues now and have a much easier simpler controller installed, just 5 simple PAS levels and giving approx 13,20,33,50 & 100% power option with no need to play with other programming settings.


You have to be careful with the throttle usage as it will blow the controller if you peg it open on a hill more so if the gearing isn't low enough.

 

[vfr400]

Almost certainly the settings. Under the pedal assist tab is slow start mode and start current. After that is the keep current. You need to find out what your settings are.

 

[NotWellInformed]

Thanks for all your help. I'll have to get one of the cables, does the software work on a mac?

So when going up a hill it's best to have it in a low gear and pedal faster? I feel like my legs will be spinning like crazy! Also isn't the motor less efficient in a low gear?

The crank rotates backwards freely.

I think a bigger chain ring will also help but I'll check what my cadence is on the flat on the highest gear in my way home.

I'd rather not use the throttle at all, I only plugged it in to see what the difference was and it gave the boost that I was expecting the pas to give.

 

[Nealh]

BBS01 will blow if gearing is too high especially on hills or off road at slow speed, be warned. Select your gearing to suit you needs, if necessary fit a double to the front. Expect chain line to be out and not all gears to be useable due to cross chaining but worth a look and see. Double chain ring works better if you have hub gears.