How to drive on e-bikes with mid-drive motors (Bafang)

[programmer001]

I use my new mid-drive (Bafang 750W) e-bike about two months.
The are a few important questions,
and I don't know the valid answers.
1) How to switch gears from one cog to another?
By pedals or by throttle?
It seems by pedals is more soft.
But I use the motor to change gears.
2) How to start movement?
Maybe it is better to start on a big cog?
But it is extra headache to switch gears before start.
Suppose I will always drive on a small cog?
RPM of the motor is not big.
Maybe it is good for the motor?
But it is certainly bad for the cassette.
3) Is it reasonable to change gears often?
Frankly I am lazy to change often gears.
I usually drive on some middle cog, if I drive about 25 km/h
on the flat surface, especially with obstacles, where I should often decrease the speed.
But the RPM of the motor in such manner is big.
Maybe it is not good for the motor?
I change gears to a big cog only to drive to a hill.
I change gears to a small cog only if I intend to drive
on a flat surface or downward a few kilometers.
I think if I often change gears the shifter and derailler is wearing out quickly.
4) There are 3 assist levels on Bafang by default.
If I use the level 3, my wattmeter shows me about 23A and 1100W.
Is it normal for the motor? Or is it risky for it?
So what are the best rules to drive?

 

[panurge]

1) How to switch gears from one cog to another?
By pedals or by throttle?
It seems by pedals is more soft.
But I use the motor to change gears.

-Upshifting at low power levels are good with both methods
Downshift with pedals only, (I use a button to the rear brake sensor to interrpt power while downshifting or anyway when power is not wanted)

2) How to start movement?
Maybe it is better to start on a big cog?
But it is extra headache to switch gears before start.

- YES absolutely, as with any bike, what about starting to downshift before to a stop?

Suppose I will always drive on a small cog?

- mmmh so why not a single speed, and so why not a direct, solid, rear hub? :wink: )

RPM of the motor is not big.
Maybe it is good for the motor?
Bad it is certainly bad for the cassette.

- SO do you think that a BBS of any kind could have more torque than you standing on the pedals from a dead stop? again this system is made to be pedaled, with or without pas, if you follow the general rules for a derailleur bike you will be fine.

3) Is it reasonable to change gears often?
Frankly I am lazy to change often gears.
I usually drive on some middle cog, if I drive about 25 km/h
on the flat surface, especially with obstacles, where I should often decrease the speed.
But the RPM of the motor in such manner is big.
Maybe it is not good for the motor?

-If your speed is slow and the Rpms High, that's mean that motor (controller) is happy...I've notice of only a pair of BBS that failed on the motor side (probably for manufacturing issues or extreme mods), though...Changing the chainring with a smaller one helps....

I change gears to a big cog only to drive to a hill.
I change gears to a small cog only if I intend to drive
on a flat surface or downward a few kilometers.

-That's right but you need to do the same while starting or stopping, if you want to be more kind with your system and try to extend the gears/clutch life.

I think if I often change gears the shifter and derailler is wearing out quickly.

-again try to downshift by pedals and you would not get much more wear on the derailleur by shifting....(torque at high RPMs and a faster chain speeds are where it differs from a normal derailleur bike, obviously there are derailleurs and Derailleurs and cassettes and Cassettes.....

4) There are 3 assist levels on Bafang by default.
If I use the level 3, my wattmeter shows me about 23A and 1100W.
Is it normal for the motor? Or is it risky for it?

- yes that's normal, look at the targa specs on your motor/controller, probably 48v (nominal) at 20A or 25A) and do the multiplication by yourself considering the Pack fresh from charge (50v to 58v, 12s to 14s)....also look at the programming thread or to an online manual of your display, you could change the assist levels from 3 to 9 and get a lot of more features as well

So what are the best rules to drive?

Again: be gentle with the derailleur system as you could be with your standard muscular derailleur bike
An interrupt button instead of the rear brake has been a huge improvement for me, since I often use the rear brake for a lot of micro driving corrections while in dirt roads, and don't want the E-brake there, and want sometime to shut up power for instants without to change the Assist level to 0 and without braking....a Good e-brake upgrade, allows you to get more travel on the lever, thus using the first little lever movements to act the same or even better than the power-off button.

Cheers

 

[dogman dan]

I don't have a ton of experience with mid drives, but I do have some, and I have read a lot about others with various problems, mostly the cyclones.

The common thing I have noticed, is that if you will start on the fastest gear, you should feather the throttle some, not just WOT it right off the line. This will limit the amp spike, and motor heating some if you don't want to downshift. Just the first 10-20 feet, get rolling 8 mph, then goose it.

In the highest gear, it will cause a huge amp spike to WOT from a stop. Depending on your battery, the controller may ramp it down plenty enough to keep your battery happy, or not. Just depends on the battery. The high amps 24v controller on the old cyclones was just a battery eater.

But if your battery is good, then you still make a lot of heat starting in the top gear. This is never good, but it can be tolerated. Mostly, it's just shortening your range to make heat. So

If your range is important, downshift to start. The beauty of a mid drive, is you have a choice. Uh, you know you will be stopping, It's not hard to drop 1 or 2 gears at the stop sign. You don't need to downshift more than that on the flat. If your front chain ring is 44, and your rear is 14, the top gear may still be low enough to remain fairly efficient. I'm just saying downshift if your top gear is 48-11 or higher.

Hills is different, the lower the gear you can stand to use on hills the better. Most hills, you should still be able to climb at 15 mph or more, and remain efficient and keep the motor cool enough. But if you are climbing a hill 15% or steeper, you will climb it much slower, and need to be in a 5 mph gear if you are going to ride 5 mph. And pedal, above 10% or so. Don't lug the motor up steep hills. I think you get that, but I write this because many don't understand how low gear they need to climb an extreme steep hill.

Re the wattage, It won't pull 1000 w for long when you are in the right gear. But if you ride in way too high a gear for the grade, it will. In such conditions, you could easily be making 500w into pure heat.

Take a 500w halogen light, and put your hand on the glass. Turn it on, see how long you can keep your hand on it. See how fast your will cook your motor? Hubmotor or mid drive, if you run it hard in poor efficiency rpm, you'll fry it. With a mid drive, you can downshift and never run inefficient for long. That's the beauty of it. But you need be willing to downshift at times. And you need to learn when to do it. A Cyclanalyst, or other wattmeter will make it easy to see when you are pulling too many amps.

Shifting under power I don't do at all. With my wimpy ass 250w mid drive bike, shifting under power just sounds like I'm going to break my chain. I'm sure the bike is built for it, you hear that same sound when racers shift going up hills. But what I don't have, is a guy that changes my chain and sprockets every 500 miles for me. So I'd rather just back off the throttle a moment, pedal to shift, then get back on.

If that is too much pain in the ass for you,,, you need a hubmotor. I've got a garage full of hubmotors I'll trade you for right now.

 

[panurge]

Re the wattage, It won't pull 1000 w for long when you are in the right gear. But if you ride in way too high a gear for the grade, it will. In such conditions, you could easily be making 500w into pure heat.

Totally Agreed, I was maybe not so clear there: the 1000+ watts are normal but have to be only peaks and short bursts, If you see such a power for continuous times, than there's something wrong on your gear choice for the given duty, or you're trying to climb over 20% grades or you're trying to pull an over 200Kg trailer.....

Shifting under power I don't do at all. With my wimpy ass 250w mid drive bike, shifting under power just sounds like I'm going to break my chain. I'm sure the bike is built for it, you hear that same sound when racers shift going up hills. But what I don't have, is a guy that changes my chain and sprockets every 500 miles for me. So I'd rather just back off the throttle a moment, pedal to shift, then get back on.

Again Agreed, and again have been not so clear: Better to shift anyway gears with no-power at all, but at 1-2 assist level upshifting with motor doesn't feel as critical as at high level, with BBS at least.

 

[MadRhino]

It seems like life would be much simpler for you if you'd change your cassette and derailer for a dog shifting hub.

 

[Ypedal]

If you overshot the rpm a bit on the current gear, back off the throttle a bit but not completely, shift smoothly then throttle up again.. no need to stop the motor.

I've been riding my BBS01 lately and after finally getting it to shift smoothly in all 7 gears and hacking up a front derailleur to make a chain guide, preventing the chain from jumping ship.. i like this kit quite a bit but it needs proper shift skill or you will destroy your bicycle's drive in only a few 1000 kms.

Shifting frequently is good, it keeps your cables and shifters working.. otherwise they seize up and work like crap after about a year.. so yeah.. shift. .. shift.. shift..

If you pick the right gear and throttle/pedal combo, you should be pulling about 5 to 10 amps ( 250w to 400w average ) .. peaking at 22 amps is ok for jack rabbit starts at busy intersections and stuff like that but builds heat real fast, wasting power and killing range.. but it's fun.

 

[programmer001]

It seems like life would be much simpler for you if you'd change your cassette and derailer for a dog shifting hub.

I also have hub motor bike (350W).
But I like my new mid-drive bike very much.
Now I can drive on streets and places, where I could not drive on hub motor before.
Hills are not a problem now.
I just want to know the best "strategy" to drive.

 

[programmer001]

1) How to switch gears?
By pedals or by throttle?

-Upshifting at low power levels are good with both methods
Downshift with pedals only, (I use a button to the rear brake sensor to interrpt power while downshifting or anyway when power is not wanted)

Hmm. Why downshift with pedals only? I can use low power to downshift.
Suppose I don't change throttle position during downshift.
The power consumption (wattage) decreases after downshift.
So it looks to me as more soft action, than upshifting.
It seems upshifting cause more noise and it is a little jerky.
Or I am mistaken? Thanks.

 

[MadRhino]

I'm not talking about a hub motor. I was suggesting a dog shifting hub, the like of a Shimano Alfine or a Sturmey Archer, instead of a derailer. A dog shifting hub can be shifted at rest and doesn't need tuning.

 

[panurge]

there are 2 major reasons to downshift without power in my mind:

1: supposingly, you would have downshift mostly while approaching a stop or a hill, and obviously you need to turns pedal while shifting....if you are on a 11t cog when doing that your bike will get an huge power push, that could be very dangerous at that power level (1000+watts) and since you are supposingly decreasing your speed, this turns into a very hard shock for the transmission/controller....I would act a brake lever (or a power-off button) while downshifting, this way I may even do that the last 5 meters from the stop or red light without the risk to power up the motor instead of stopping.

2: Downshifting (the chain derail to higher teeth cogs) is anyway the most "problematic" direction to shift even with a muscular bike....the gravity, the more teeth to engage (so longer derailling time) and mostly (that's the same for your middrive) because of the conditions you usually need to downshift: decreasing speeds, slow speeds, or more torque demand.....last but not least, there's the Chainline on your system, that typically is more on the low count than higher count cogs.

Have not experience with an IGH hub and middrives but it sounds to me a good option, if not for weight and costs....

For some people it should even have sense to put the BBS in a single speed bike....If someone has not to climb a lot, but still want a central weight for better handling and hates kinetic and gyroscopic effects and unsprung weight on the wheel, it is still an option.....there are also SS MTB machines on the tracks sometimes.....I bet these riders would go eventually single speed with a middrive system...

Also, I know a guy that has a Cyclone on a DH bike and since he use that bike anyway not for climbs, and before to convert it he used only 3 cogs....now he ditched all the derailleur system and switched to a fixed, spring loaded tensioner. (because of the suspension) I've helped him with this build and I was skeptic...but I have to say that's a pretty cool and light machine....(well not mine anyway )