Bafang, minimalist approach?

[emco5]

I’ve not been able to get a ride on a BaFang-equipped bike so am having trouble guesstimating the power output I’d get from their 350 watt system. About a dozen years back I had a Currie “Pro Drive” MTB with planetary-geared motor mounted on the left of the chainstay. I was told it was 450 watts, and it was strong enough to only need pedal assist on the steepest hills. My last e-bike, two years ago, was an iZip "Via Rapido". It was a pleasant riding bike, but its 250 watt hub-motor was useless on even moderate hills. I'm thinking that Bafang's mid-drive using the bike’s gears should be a very noticeable upgrade over those two designs.

75% of my commute needs no assist, so I’m hoping to take the minimalist approach to e-power and keep the motor/battery weight as low as possible. Speed is not a priority, I just want help cresting the local Alps [as much as 26% grade] without needing a shower. Would the Bafang 350 and 36v 11-amp battery turning a 32t granny on a 26” MTB with 170# rider be enough?

 

[nutnspecial]

I've no direct experience with Bafang or other serial middrives, but from what I've read and seen, I would say that's a very reasonable assumption/plan.

For climbing, surely a 32 is a great place to start, and I assume there are 36/38t low also available such as in standard cassettes.

For the lightest weight pack able to give any reasonable power, you might find a 5ah lipo pack great for shedding weight, depending on the total watthours you'll desire of course.

 

[motomech]

I’ve not been able to get a ride on a BaFang-equipped bike so am having trouble guesstimating the power output I’d get from their 350 watt system. About a dozen years back I had a Currie “Pro Drive” MTB with planetary-geared motor mounted on the left of the chainstay. I was told it was 450 watts, and it was strong enough to only need pedal assist on the steepest hills. My last e-bike, two years ago, was an iZip "Via Rapido". It was a pleasant riding bike, but its 250 watt hub-motor was useless on even moderate hills. I'm thinking that Bafang's mid-drive using the bike’s gears should be a very noticeable upgrade over those two designs.

75% of my commute needs no assist, so I’m hoping to take the minimalist approach to e-power and keep the motor/battery weight as low as possible. Speed is not a priority, I just want help cresting the local Alps [as much as 26% grade] without needing a shower. Would the Bafang 350 and 36v 11-amp battery turning a 32t granny on a 26” MTB with 170# rider be enough?

I've never had a Currie, but I don't think one can pass judgement on a modern system, whether it be a hubbie or a mid-drive on that experience.
As for your hill, on one hand the word Alps and "26% grade", says extream. But one the other hand, you say you can pedal it. Conflicting for us not there and more real data is needed.
In general, a low speed (201rpm) mini hub on 48V will climb steep hills, but not long ones.
For longer, steep hills, a larger hub or mid-drive would be the way to go.
But it would be a mistake to think that any type of system that can offer real climbing ability can be used as an on/off system. Once installed, the system is there and you will feel it if you try to pedal system off. The way these systems are used if pedal assist is important, is to power to a level somewhat below desired speed and add with legs to add speed. I believe the only realistic on/off system would be a friction frive on a road bike.

 

[nutnspecial]

It's true any system will add weight, but I'm thinking he is planning on maybe 20lbs extra (w/battery)? Sure the weight and added mass will factor into additional rolling and air resistance, but middrives characteristically have no cogging when not in use? My bike is noticably harder to get moving with wider tires and 35lbs(+) more weight, but if I pretended I just weighed more, man would my legs and cardio would be stronger. Of course, I'll never be able to output 6kw naturally, so the extra weight is worth it when in use.

I'm not sure how a standard friction drive would do for torque over speed, but yep, it's the lightest possible system (so far). Hey emco, that reminds me, there's a guy named Dave with a cycloidal middrive on here- i think it weighs notably less than the bafang, and can handle more power if desired. I was pretty impressed with it.

 

[emco5]

Thanks for the feedback, guys.

 

[alfantastic]

Would the Bafang 350 and 36v 11-amp battery turning a 32t granny on a 26” MTB with 170# rider be enough?

Why not just go for the BBS02 48v 750w. It's easier to turn down the assistance if it's a little too much, than try to squeeze more out of a 350w if it's not enough.

 

[emco5]

Nutspecial wrote:
> For the lightest weight pack able to give any reasonable
> power, you might find a 5ah lipo pack great for shedding
> weight, depending on the total watthours you'll desire of course.

Thank you.  Now I can obsess over that for a while.


Motomech wrote:
> ….it would be a mistake to think that any type of system that
> can offer real climbing ability can be used as an on/off system.
> Once installed, the system is there and you will feel it if you
> try to pedal system off..

I’m still looking for confirmation, but apparently there is very little, if any, crank drag with a Bafang when the power is off.  The system weight would be felt and that is a focus.


Alfantastic wrote:
> .... BBS02 48v 750w. It's easier to turn down the assistance if
> it's a little too much, than try to squeeze more out of a 350w
> if it's not enough.

No doubts that a 750 would probably be more than enough.  If it has the muscle via the bike's gear train, I'd rather go with the smaller-cased 350 motor and a minimum/lighter battery.  Too much power assist paraphernalia can make a lively bike feel like a moped, and why haul excess bulk around every day if it's unnecessary.  Sometimes less can be more. 

 

[Fastest1]

I run a BBS02 on an old road bike. I am not running low gears. In my highest gear 52/10 I get 32mph tops with no assist on flat ground. I weigh 250lbs.
I think that the 350 & 750 watt models share the same casing. That being said, I added 16lbs to the stock bikes weight total. Mid drive and battery. There is a parasitic drag no matter what. I am not talking about the added weight.

 

[footloose]

My situation is similar to yours. Live in very hilly area (SF peninsula), 175 pound rider, want some help with hills.
Have a couple bikes with variety of motor setups (Q100, MAC10T, BBS02/750).
My favorite all around bike has become the BBS02 in conjunction with a Nexus 8 internal gear hub.
I run it mainly with a custom battery pack from EM3ev -- '48V' 14S/3P pack built of the high-discharge Samsung SDI INR18650-20R cells. Pack is very small -- just 5.85 Ah, 2.1 kilos.
Given that I don't use power when going downhill, use it moderately on flats, use it heavily on uphills...
I'm finding my effective range on this pack is 12+ miles. Very reasonable for my commute or grocery-getter rides.
Setup has ample power for climbing pretty steep hills, no complaints.

 

[nutnspecial]

There is a parasitic drag no matter what. I am not talking about the added weight.

I thought serial (crank) middrives used a freewheel just like I use on my parallel build? The added drag from that would have to be less than 1/10th of a percent of the added aerodynamic and rolling resist losses? Even on the 7lb kit by tangentdave, with a 5lb battery. I'm guessing the 350 bafang kit is about 7lbs also- dang I wish my bike was still light

 

[emco5]

.... Even on the 7lb kit by tangentdave...

Okay, I looked up tangentdave. He's in my city and the hill he rides in his video [26th and Roy] is the 26% grade in my mind in the original post. He flies up! I cannot do that one without zig-zagging, resting, sweating, repeating. I doubt even a 750 watt BaFang would move like the Tangent. It's beyond minimalist, but I hope he continues to develop it.

https://www.youtube.com/watch?v=OxCQceYGBQQ

 

[nutnspecial]

Lol, yeah, it's an interesting drive, minimalistic in weight anyway?

Price is close to triple the 350w bafang, and with higher power requirements (for full potential) and maybe noise.
Still, it's capable of 10x the power?

Anyway, the 350w bafang should work great for what you want imo, and properly geared for optimal motor revs, the 350 will just go a bit(10x?) slower on that bigass hill. Unless it's underrev'ed, it will hold up just fine to whatever slope.

 

[2old]

Haven't weighed them, but I read that the 02 was just one pound heavier than the 01, so the total weight difference is that pound plus whatever the 36V vs 48V battery adds.

 

[FastJohnny]

I cant speak to the 36v system, but I can give you an idea of what different gearing feels like. I have the BBS-02 48v 750w on a 29er hardtail. I've ridden it on and off road, with multiple setups.

First some stats:
Bike 50lbs with battery
Rider 210lbs
Gear 15lbs (hydration pack, tools, tubes, etc)


48t Ring 11-34 Cassette
With the stock 48t chain ring that comes with the bike it felt geared WAY too high for the singletrack I was riding, also the chainline was off a bit. It would climb any of the hills you'd find on the road but not everything you would find off road.

42t Ring 12-36 Cassette
alcedoitalia.it makes a 42t chainring for the Bafangs that not only lowers gearing, but perfectly corrects your chainline. The Lekkie Bling Ring is another ring that does the same thing that you dont need to order from Italy. This setup was great for anything road, you can throttle only up the steepest hills at 18-20 mph in the middle of your cassette range.

34t Ring 12-36 Cassette
using the BA-104 adapter, and a raceface narrow wide chain ring, you can achieve some ridiculously low gearing that will let you throttle up 100% grade (45 degree angles) for short distances of 15 feet or so. I'm talking stuff where you would need to put a mountain bike on your bike and hike up using your hands. The down side is the chainline is now back at stock as its impossible to make an offset ring at 34t. This setup is totally pedalable off road with a speed range of up to 20mph pedaling. Probably too low for the street.

Here's how I have the power assist setup.

Level 0 - no assist, this is what I call "hard mode", If im riding with a friend who sucks, this is where I set it.
Level 1 - 11% assist. This makes my bike feel like its 32lbs again, and offsets the weight difference of the motor and battery
Level 2 - 20% assist. Now this 50lb MTB is as easy to pedal as a 15lb road bike. Great for riding with riders better than myself
Level 3-9 - various degrees of super hero.

I have throttle set up in any PAS level.