Questions of effeciency comparison in bafang mid drives

Hello and first of all greetings to everybody here in the endless sphere forums & cudos to all the hackers, innovators & inventors - You make this place happen!

First time poster, but I have been trawling the site for the past few weeks in hopes of improving my transport situation & I'm feeling hopeful.

I'm wondering if i can find help with a few things...
The more range I can achieve the better but my average commute is 50 km which is mostly flat with with a 60 meter climb over about 4 km towards the end.
So at the very minimum I need to be able to cover a 50 km distance with confidence.
I am already an avid cyclist so I'm looking mainly for a PAS boost to cover this distance with less effort and sometimes to be able to do small upto 20 km journeys with even less effort. Good speed & torque is desirable but I'm willing to slow down to cover the greater distances.
Since I started investigating the subject some weeks back I have looked at many solutions and have come to the conclusion that a mid-drive kit would be best
suited to my needs. Up until yesterday I had my heart set on a bafang 48v 750w mid drive kit.
Unitll I researched further and couldn't find adequate information on efficiency potential in the range of bafang mid drive kits (36v - 250w,350w,500w & 48v 500w,750w).

I wonder does anybody have data on the efficiency of each kit for a given battery size (I take that it is scalable~ 5ah battery will provide 50% the distance of a 10 ah battery) ie Distance covered/speed/PAS level/battery size. Or even w/km for each kit.
Also could anybody recommend a battery size for covering these distances for a given kit. I just cannot figure out which kit is more suitable to my needs.

I hope that the question has not been posted before and the post is in the right thread. If not maybe a mod will help to point me in the right direction. And if need be suggest a more suitable subject line

Thanks for your time Y'all I hope to make this a new hobby and eventually be able to contribute to the forums myself.

I measured the efficiency of my BBS01 250W 36V once over a varied road, back and forth, 8,4 km total. I used a Watt meter to measure input and a powertap rear wheel to measure output. The average efficiency was 78%, which is what's in the specs. The average speed was 20 mph and the average power in/out was 280/218W. Throttle only, no pedalling.

Wh per km/mile is too dependent on rider position, parasitic bicycle drag, rolling resistance and weather ++ to make good comparison data in my opinion. I can probably get by with half the battery capacity of another rider because I sit in an aero position on my CX-bike while he sits upright on a hybrid.

tahustvedt said:

The average efficiency was 78W, which is what's in the specs. The average speed was 20 mph and the average power in/out was 280/218W).

Click to expand...

That is to say you used 280watt hours on the journey?
I shall take into consideration aerodynamics to increase my range.

What battery are you using?

Thanks for your input

I meant 78%.

I used 80.4 Wh of electrical energy.

My battery was a 6 Ah lipo. Now I'm using a 5 Ah lipo and ride minimum 30 km on one charge.

Some of the data I recorded: http://endless-sphere.com/forums/viewtopic.php?f=28&t=50104&p=914424&hilit=78%25+efficiency#p914424

Speed has a big impact on how much battery you use. How fast do you want to go? I've seen loads of discussions about battery range and efficiency during the five years I've been involved with electric bikes. It's a compete waste of time asking what other people get if they're pedalling and the speed is in the range 10 to 20 mph because there's so many factors, which they often conveniently leave out.

tahustvedt said:

I meant 78%.

I used 80.4 Wh of electrical energy.

My battery was a 6 Ah lipo. Now I'm using a 5 Ah lipo and ride minimum 30 km on one charge.

Some of the data I recorded: http://endless-sphere.com/forums/viewtopic.php?f=28&t=50104&p=914424&hilit=78%25+efficiency#p914424

Click to expand...

That's great info, So you are getting with your riding style 4.78w/km. Were you using PAS or just throttle only. If so how much effort would you say you had to put in?- what would you say your riding style is like apart from aero leaning?

I wonder how the 750w or 500w bafang would fair under the same circumstances in terms of efficiency.

d8veh said:

Speed has a big impact on how much battery you use. How fast do you want to go? I've seen loads of discussions about battery range and efficiency during the five years I've been involved with electric bikes. It's a compete waste of time asking what other people get if they're pedalling and the speed is in the range 10 to 20 mph because there's so many factors, which they often conveniently leave out.

Click to expand...

To be honest d8veh I want to go as fast as I can while being able to cover these distances and at the same time afford the equipment.
like I said "Good speed & torque is desirable but I'm willing to slow down to cover the greater distances."

The main reason behind this post is to figure out which bafang mid drive kit is most efficient in terms of wh/km. And possibly it's optimum speed efficiency.
I understand that there is a variety of contributing factors involved.But If I cannot get any proper answers any and all information from users of these motors is useful. in terms of how far it gets them and with how much juice.

Thank you also for your input.

I think you couldn't find any informations you want.
The efficiency depends on too many things.

Even if people give you efficiency for a speed like 10Mph, the efficiency depends on the speed's motor and then of the gear used !!

That's why I chose BBS02 48v 750W, it can provide the maximum of power if I want but if I don't want, I can just use it as if it was just a 250W or 500W. AND during time and some experiment, I could know which gear for which speed. And we can change the efficiency only with a mid-drive motor.

Just choose the BBS02 750W 48V, buy a 10Ah battery and make some experiments. It's the only one and fastest solution to know in one week how you have to use your throttle/PAS for your use and your commute.

Hi alexis57
I understand what your say about gear related efficiency.
But in terms of operating the 750w at lower wattage - as far as i know it is wound to produce the same rpm as the other models for the given top wattage and thus operating the 750w at 500w or 350w would produce considerably less rpm. So it is no way to gauge it.

If i can get feed back about the motors It would give me -some- idea what to expect & help me to make a decision

None of the motors are any more or less efficient than the others. if you have the high powered one, you can alwsys turn the power down. You can't turn it up on the low powered version, so it's a question of how much power you want.