Bafang Programming - Amps in each level

[PsilocyBen17]

Bafang Motor Reprogramming Help

Hi All,

I'm having a problem with the a bafang motor I just purchased. I recently bought a new recumbent trike and equipped it with a 750w BBS02. I find the settings out of the box to be fairly unusable. As i like to bike tour I tend to make settings that draw low amps in order to preserve battery and go further.

I reprogrammed using the bafang config tool. The settings are something like this:

Low Battery Protection: 41

Current Limit: 18

Level 0: 0

Level 1: 10

Level 2: 20

Level 3: 30 etc...

All speed limits are set to 100%.

So, with this programming I would expect to see the controller draw the above percentages of the current limit....1.8 amps in the level 1, 3,6 in the first level, 5.4 in the 3rd level, etc. with the controller rounding up or down to the nearest .5 (it doesn' t display decimals unless they are .5)

The problem I'm having is that the controller doesn't want to seem to draw those amperages. It draws between 0 and 0.5 in 1. 1-1.5 in 2. around 2 amps in 3....

I ran this same programming on my old bike with the same model of motor and custom programming. I loved the 3rd setting. it was my go to setting. Now I have to crank it all the way up to 6 to get the same power.

Whats up with this? Could something like "keep current" be causing this? My new bike is heavier with bigger wheels, tires, and gearing. Could that be having an effect? Should I reset the settings and try again? Any help would be MUCH appreciated.

 

[HumanPerson]

Hi, @PsilocyBen17 and Welcome to the forums

 

[m@Robertson]

Clever screen name @PsilocyBen17

Take a look at this:

BBSHD Programming For The Pedaling Cyclist (2023 Update)

Explore enhanced BBSHD programming for pedal assist settings that don't let the bike run away from you, and throttle settings gentle on the drivetrain.

talesontwowheels.com

The relevance to your situation is what is described with respect to what the use of Current Decay does to overall power output. Its a straight up pedal assist power dial, although its not generally understood as such. By changing only Current Decay I can have a max of 400w/6a pedal assist max output, or 1000 and correspondingly increased amps.

 

[PsilocyBen17]

Hey, thanks for your response…

I’m sort of new to this but my understanding of the current decay setting is that it will drop to a specified % once you are pedaling fast.

If its set to 80% it should drop to 80% of the amp limit in that level.

Maybe you could see if my math checks out…

Current Limit [A] 18
Assist Level 2: Current Limit %: 15
Assist Level 3: Current Limit % 18

So, the max i can draw is:
15% of 18 in Level 2 (2.7amps)
18% of 18 in Level 3 (3.2amps)

but, keep current will mean that i’m only drawing 80% of these figures once a certain pedaling cadence is reached:

2.1 in Level 2
2.5 in Level 3

I only used the most common levels in these examples… And both speed limits are set to 100%.

Thanks for your help on this. I’m kind of stumped as to why my old bike did not perform this way, with the same settings programmed!

 

[PsilocyBen17]

Ah. I realize the above post is about the "keep current" setting. Not current decay as you mentioned. Current decay is set to 8 so my understanding is that amperage shouldn't drop until im pedaling hard...

 

[m@Robertson]

Ah. I realize the above post is about the "keep current" setting. Not current decay as you mentioned. Current decay is set to 8 so my understanding is that amperage shouldn't drop until im pedaling hard...

Thats the common thinking on the subject, but there are subtleties not documented and largely unrealized it seems. Surprising on a system that has been pored over so thoroughly, for so long by so many.

Bear in mind Bafang documents NOTHING (and actively discourages any form of settings changes) so everything you read is a different someone's expert take based on their own tinkering. Current Decay is not supposed to be a power dial. But I found this to be an additional feature that I never expected.

And while thats just more tinkering from one more self-appointed expert, you can easily, empirically test it for yourself. It will help if you have an 860C display, which I believe is the only one that will let you see simultaneous real-time watt AND amp output.

Also I suggest if you want to verify this added property of Current Decay, duplicate every setting I did in that article. Then vary Current Decay as described. Not because I have done something brilliant but to eliminate variables. Its entirely possible there are other interactions that are similarly undocumented.

With that said, you say your Current Decay is set to 8, which based on what I describe in that article will reduce both your peak and sustained PAS power output to much lower levels (but will not affect throttle output). Try kicking it down one number at a time - change nothing else - and see if your pedal assist values don't incrementally increase.

 

[m@Robertson]

I’m sort of new to this but my understanding of the current decay setting is that it will drop to a specified % once you are pedaling fast.

If its set to 80% it should drop to 80% of the amp limit in that level.

That is the common understanding, yes. I have found that something like an 80% cut is not noticeable. You have to get serious and mine are 40% and 30% respectively, depending on if I am doing the low power or the hi power pedal assist config. When I am spinning, only a big cut has any real effect that I can feel, and I like what I get with these settings.

Maybe you could see if my math checks out…

Something I say in that article is if you are trying to get precise with power output level measurements, this is wasted effort. Part of the reason for this is they can be moving targets by their nature (your removal of the Speed % parameter's functionality takes a lot of that variability out of the picture, since speed %'s effect varies by battery voltage). Part is also due to the fact that nobody really KNOWS anything. Nothing is documented, and behavior is all based on inference after observation by people who do not have actual manufacturer's access to the internals.

Instead, I focus on coming up with settings that focus solely on my desired ride experience. Very little assist at lower levels. High assist at upper levels. Enough incremental difference between each so I don't have to jump from 2 to 9 to get some decent help when I hit grades. Next, when I stop pedaling I want the motor to stop immediately. Same with when I release the throttle, and I want pedal assist and throttle both to roll torque on very gently. And a strong cut on pedal assist when my crankarm rpms go hi. Etc. Different preferences for everyone the key for me is I am solely working on ride feel and I ignore the numerics.

I only used the most common levels in these examples… And both speed limits are set to 100%.

I know a lot of people do this, but I don't and don't recommend it. You're selling yourself short UNLESS you are programming for an MTB and want to proof yourself from power cuts on steep soft slopes. That is a scenario where setting speed % to 100% across the board prevents that cutback.

I’m kind of stumped as to why my old bike did not perform this way, with the same settings programmed!

Bafang firmware is a moving target. Its not enough that there is no true documentation for the settings, whose effect is all guesswork (just very good guesswork since so many have been at it for so long). Additionally Bafang will change motor behavior with firmware revisions. If you dig into one of my old BBSHD articles - probably the original one - you'll see I show Pedal Assist settings that used to work great at one point years ago and then at some point ... sucked. That was a firmware upgrade. It doesn't stop with Bafang. Resellers with the right toolkits can make major changes that you are locked out of. California Ebike has locked a 52v BBSHD I bought from them to 28a instead of the usual 30a I get on my 52v Luna BBSHDs. And the Cali Ebike motor has a power tap Luna motors don't. Bafang will build all manner of changes into an order... if its big enough.

 

[PsilocyBen17]

Hi M@,

Thanks for your thoughtful and thorough response. You’re a great resource on the forms. I like what you say about “ride feel”… one can drive themselves crazy, looking at power output in certain levels, etc.

A couple questions:

1. Why do you enjoy using speed limits? Is it because you use it as a way to cut power when pedaling fast? initially I took it off because I found it frustrating when the motor would cut out but maybe I need to give it a second chance.

2. Good point about firmware, interesting to hear about the thing politics and their stance on mods. I noticed that both controllers I am comparing have different firmware versions… I can see how this would make a huge difference if everything we are doing here is citizen science.

Are any aftermarket controllers available? Are their “better” controllers than what come stock with a bafang motors?

3. in your previous post, you mentioned turning down the current decay setting. In thinking of current decay like a volume knob, I was thinking that higher settings (like 8) equal more power. If that’s the case, wouldn’t turning down the current decay lead to less power outputs with pedal assist? Perhaps I’m mistaken.

Thanks greatly for your help!

 

[m@Robertson]

I'll go by the numbers.

1. Why do I use speed limits?
First of all, Speed % on the Pedal Assist screen is referring to the rpm speed of the motor, not the land speed of the bike. The Current % setting is the one that is based on road speed. Which is not exactly intuitive.

Maybe a better way to address this is to mention why people started NOT using Speed %: They didn't want power cuts when humping it up a hill on gnarly singletrack. And that makes sense. In uneven, steep and loose terrain the last thing you need if you put on a sudden spurt of crank rotation is to get a power cut because the motor thinks that, since you can spin the crankarms, you don't need power assist. That is also why you would minimize the separate and interrelated Current Decay.

If on the other hand you are street riding on flat-ish pavement, then increased cadence is a much better indicator of not needing power assist. So yes I use it as a way to cut power when I am pedaling fast. By pedaling fast, in my paved, flat street environment, if I am able to spin the crankarms I have demonstrated I can do the work without assist. A cutback noodges me to slow my pedal cadence with an upshift, which gets me going faster, too. Either that or I cut back on the power by going to a lower pedal assist value, like from 3 to 2 for instance. That will slow my cadence while I stay in the same gear, since I am getting less assist. Since as noted earlier I try to design my setup to have noticeable differences from one level to the next, I should be able to find a happy medium (where my cadence rate and effort level reach a point where I am happy with it) using one or the other.

Super important to realize here: My ground speed is not a determinant in what I am doing during the ride. I am shooting for my optimum comfortable cadence and effort level. Again: going for a good ride feel. Land speed will be what it will be when I get in and stay in that zone.

2. Firmware
Remember also its not necessarily something that comes from Bafang. Large resellers have access to a level of software that we don't with the common tools we all have.

3. Current Decay.
I think you have it backwards and thats why you're having trouble seeing this right. Turning Current Decay UP (to 8) turns the power cut up, too. Turning Current Decay DOWN increases the power (because it decreases the cut). Its not a volume switch. Its a dampener. So a higher setting gives you more 'decay' and a lower setting gives you less.

The 2023 programming update I posted is light on explanations for all the settings. My original one written in 2021 goes in the other direction and tries to explain every setting. I did try and update it over time though, so some misconceptions circa 2021 got wiped away. I also updated thesoftware screens so among other things you can see that amazing graph that does such a good job of explaining the effect of all the settings. The software update it goes with kind of sucks, but that screen with its graph does great work explaining what each setting does.

BBSHD Programming For The Pedaling Cyclist

(But Not For The Throttler) There is a follow-on to this article that tinkers with these settings a bit further. In August 2023 I published another update that passed along what I’m doing dif…

talesontwowheels.com