Which Bafang to get?

M

mingonn

10 W
Joined
Oct 9, 2007
Messages
83
Hi all,

I want convert my 20" folder into an electric. Goal is at 25 km\h on the flat and I am using a 44v (lipo) pack but have a 48v Ping on the way. We have a crazy 200w limit here in OZ so I would like to stay as close as possible to that (I am reading it as 200w on the flat rather that the silly peak value that it is supposed to be). There are quite a few motors listed and theyseem to be 24 or 36, I am guessing the 36v will do what I want but not sure which model. Will be going front wheel drive.

Trying for a super light e-commuter.

Cheers
Derek
 
Howdy Derek,

Using this as a rough guide, for 25km/h it looks as though you'd need to run a 36V 16" motor at 48V in a 20" wheel.

Is 25k's your optimum speed, or would you want something that could go a bit faster? :twisted:
 
I had a look at that table but couldn't work out the numbers, wasn't sure if they do different windings and gearing for each voltage/wheel size or its one size fits all.

Trying to set up the perfect light weight commuter, I mainly ride on bike paths so any more than 25 km/h gets a bit hairy with pedestrians and pets around, but being able to wind out to 30 km/h on the road would be good.

So 25 km/h is the speed I want to be cruising at most of the time and have the motor running around peak efficiency. I figure a bit more torque wouldn't hurt with the hills and acceleration anyway.

The 200w law has me a bit worried though.

Derek
 
Derek,
I am using a Bafang motor @ 36v on my trike. It is a rear motor (not sure on the model though)
Original spec was 200 w @ 24v.
I have used this motor on both a 26" and a 20" wheel.
On a 20" wheel, this little motor is good for a 30 - 35 kph cruise, and torque is quite good.
In a 26" wheel, the trade off is less torque, and cruise is only marginally higher, say maybe another 3-5 kph, but with some healthy pedaling, I have seen over 50 kph, and could still feel the assistance from the motor!
IMO, these are great little motors, and I have heard that they can be overvolted further to 48v, with the appropriate controller.
FYI, I am using 36v/10 AHr of LiFePo4.
 
can somebody tell me, which Bafang i have ?
(i know there webpage, but it does not realy help me)

i konw its geared, it says 180W (with 24V) on a sticker (but i think is is maybe just from the supplier, because he sells the very same motor also for 36V)

and it looks like this:
Nabenmotor_mit_Felge_klein.jpg


Fahrrad_Seitenansicht_VorderseiteDSCF2063.jpg


iam currently using it with 14,8V which gives some gentle assistance on my 16%-hills...

(the supplier says it can handle up to 48V..
i initially wanted to use it with 36V but now, after the experiences with 14,8V i think i will only need 24V for my hill-climing...
higher volts bring the rpm to too high values and than its maybe not as good for hillclimbing anymore)

here with battery:
batteryweight: 76g (gramm !)
Akku_klein_am_radl_DSCF2650.jpg

(the battery is the very little, tiny yellow box on the center-frame -> 11V and 1,35Ah -> enough for some little assistance for my 100m high hill-climbing at 10-15%)

yes, this realy does work:
http://www.kraeuterbutter.at/Bilder2/Radnabenmotor_Vorderreifen/Testlauf%202/Spannung_Watt.jpg
http://www.kraeuterbutter.at/Bilder2/Radnabenmotor_Vorderreifen/Testlauf%202/Spannung_Hoehe.jpg
http://www.kraeuterbutter.at/Bilder2/Radnabenmotor_Vorderreifen/Testlauf%202/Spannung_Ampere.jpg
http://www.kraeuterbutter.at/Bilder2/Radnabenmotor_Vorderreifen/Testlauf%202/Hoehe_Stromverbrauch.jpg
gives on my hill some ~120Watt inputpower, so maybe 70-80Watt to the wheel..


so: i would be pleased when somebody could point me the direction WHICH of the bafangs it is..
thx..
 
That looks the same as my bafang.
http://s281.photobucket.com/albums/kk204/freddyflatfoot/Trike/?action=view&current=DSCF0073.jpg
http://s281.photobucket.com/albums/kk204/freddyflatfoot/Trike/?action=view&current=DSCF0074.jpg
http://s281.photobucket.com/albums/kk204/freddyflatfoot/Trike/?action=view&current=DSCF0078.jpg
Also, from the Bafang website, this should be your motor,
http://www.szbaf.com/en/product_detail.asp?ProductID=507
 
Freddyflatfoot said:
Derek,
I am using a Bafang motor @ 36v on my trike. It is a rear motor (not sure on the model though)
Original spec was 200 w @ 24v.
I have used this motor on both a 26" and a 20" wheel.
On a 20" wheel, this little motor is good for a 30 - 35 kph cruise, and torque is quite good.
In a 26" wheel, the trade off is less torque, and cruise is only marginally higher, say maybe another 3-5 kph, but with some healthy pedaling, I have seen over 50 kph, and could still feel the assistance from the motor!
IMO, these are great little motors, and I have heard that they can be overvolted further to 48v, with the appropriate controller.
FYI, I am using 36v/10 AHr of LiFePo4.
Click to expand...

Hi Freddy,

Those are amazing numbers, how did you go about getting your motor? Can you let me know how much I should expect to pay for one delivered to sunny Melbourne? Did you have any trouble fitting it to the rear? I read somewhere that they are a lot wider than normal, do you know what width your rear hub is, 130 or 135mm?

Great to hear you have had a good experience with this little motor.

Cheers
Derek
 
Derek,
The motor kit was on Ebay, and actually from a company in Melbourne!
Evehicle, I think.
http://www.evehicle.com.au/
Will probably cost a bit more than what I paid on Ebay, but after getting the motor, more than happy with it!
You could also try Brett at
http://www.users.bigpond.com/solarbbq/bikesale/bsale.htm
He doesn't have the Bafangs on his website, but I'm pretty sure he can get them for you, just drop him a line.

I'm pretty sure the motor that I have is actually a 24V/200w model for a 20" wheel, running at 36v on a 36v controller. That explains the extra performance, as power is actually closer to 350-400 watts. (36v x 15A draw = 540 watt max!)

Kraeuterbutter, sorry, I don't understand your question?
But you do have a very lightweight solution! can't imagine the range would be much though, ;)
But at higher voltages, you should get higher speed and higher torque.
 
@Freddyflatfoot:
my question: its what they say on the link you gave me..
my English is not that good and i don´t understand what they mean with that sentence..

for more speed and torque..
more speed (with higher volts) for sure..

more torque: iam not sure..
the bike-controller i have is rated 7A cont. and 14A short
i suppose: if the currents want to go higher it limits the current to 14A, right ?

i already get 12-14A with my very little 11,1Volt Lipo

so on the same slope (20% !): with 36V the current would be - whooohooo - 50A ??
the motor would maybe burn

the controller would limit the current to 7A (or 14A, not sure about that)
to do this, he has to throttle down..

effect: at the end i have the same torque and speed, but worse efficience..

of course: on a not so steep hill the current may be 7A or 14A at much higher speed, so the controller does not have to throttle down and the over-all-power is much higher than on my setup..

i hope i can test this theorie tomorrow ;)
 
Im about to lace a rear geared Bafang into a 20" wheel. U need about 170 mm width, which on a steel rear fork is quite easy to spread to! I have a rear suspension trike, so I just get a Goodwill suspension bike and remove the rear triangle. Makes it much easier to work on. Most rear triangles can be adapted with a teeny bit of u alloy to my Tricruiser. I spread with a threaded rod and nuts and washers, then parallel the dropouts with a BIG adjustable wrench! I can get 200 mm without breaking a sweat or the triangle!!!!
otherDoc
 
Kraeuterbutter said:
@Freddyflatfoot:
my question: its what they say on the link you gave me..
my English is not that good and i don´t understand what they mean with that sentence..

for more speed and torque..
more speed (with higher volts) for sure..

more torque: iam not sure..
the bike-controller i have is rated 7A cont. and 14A short
i suppose: if the currents want to go higher it limits the current to 14A, right ?

i already get 12-14A with my very little 11,1Volt Lipo

so on the same slope (20% !): with 36V the current would be - whooohooo - 50A ??
the motor would maybe burn

the controller would limit the current to 7A (or 14A, not sure about that)
to do this, he has to throttle down..

effect: at the end i have the same torque and speed, but worse efficience..

of course: on a not so steep hill the current may be 7A or 14A at much higher speed, so the controller does not have to throttle down and the over-all-power is much higher than on my setup..

i hope i can test this theorie tomorrow ;)
Click to expand...

Think more in terms of watts, rather than Amps.
For instance, your 11.1V @ 14A is, 11.1 x 14 = 155.4 watts. The controller limits the Amps drawn, so 36v x 14=504 watts.
The only caveat, is that the controller rated voltage, must match your battery voltage.
docnjoj said:
Im about to lace a rear geared Bafang into a 20" wheel. U need about 170 mm width, which on a steel rear fork is quite easy to spread to! I have a rear suspension trike, so I just get a Goodwill suspension bike and remove the rear triangle. Makes it much easier to work on. Most rear triangles can be adapted with a teeny bit of u alloy to my Tricruiser. I spread with a threaded rod and nuts and washers, then parallel the dropouts with a BIG adjustable wrench! I can get 200 mm without breaking a sweat or the triangle!!!!
otherDoc
Click to expand...

My bafang, with a 7 speed cluster, is 140mm, so only a small amount of spreading of chain stays, so no issue there.
 
I've just bought a bafang from ecrazyman 11/7/2008 , hasn't arrived yet. Part number was 227SWXB3-2, I wanted something for a rear 26".

He couldn't supply spokes or rim.
Maybe ask Keywin on ecrazyman@gmail.com

I know the width may be bigger than regular bike, I'll let people know how I get on.
 
I found this on ebay, price isn't too bad, I have asked if they do a 20" kit but I doubt it. If it is a Bafang I might go for it , rated at 24v or I might start with 29.6v and see how it goes before going up to 44.4v.

Will drop Keywin an email and see what he can do. How much did the hub cost Gregory and what did shipping cost? Did it come with a controller, throttle, brakes?

My wife is eying off my current 20" folder so I want to convert my other Dahon but would prefer a lighter hub than the 6kg gearless one I am currently using.

Cheers
Derek
 
@Freddy:

[qutoe]Think more in terms of watts, rather than Amps.
For instance, your 11.1V @ 14A is, 11.1 x 14 = 155.4 watts. The controller limits the Amps drawn, so 36v x 14=504 watts.
The only caveat, is that the controller rated voltage, must match your battery voltage.[/quote]

and how does the controller limit amps ?
its doing it by lowering the voltage (in simple turns, its of course a little more complicated) so long, until the amps do not climb over the limit...

so infact:

i assume, that on a steep hill the motor with my rc-modell-controller (which has no amp-limitation like the bikecontrollers)
and my 11,1Volt battery pulls maybe 20A

the bike-controller limits at 14A --> effekt: on a very steep hill, were i see 11,1V and 20A on my test-setup
the 36V-Bike-setup with 14A controller will have less torque
but limiting makes a bad efficience, hot controller

so at the wheel i will probably have more Power with the 11,1V battery and 20A then with the 36V battery and a bike-controller with 14A limit

or do you see a mistake i made ?

-------------------------------

(i came to this conclusion from the other direction:
when i have already 12-15A with only 11,1V on that hill,
the same motor will suck a lot more amps with 36V at the same hill (maybe 50A)
this is not allowed by the controller (14A), he limits it )
 
The controller doesn't ,limit the voltage, they limit amps by having a 'shunt' in the circuit. Controllers can be modified somewhat, by modifying the shunt, to allow either a higher, or a lower amp draw.
You can also limit amp draw by using an add on meter, called a Cycling Analyst, which monitors all the functions of your setup. I personally don't have one, but a lot of ppl on this forum do.
I wouldn't worry too much about the controller though, just get one to match your motor and battery pack and enjoy the ride!
 
Derek,
I paid $229 USD by paypal for the rear motor, 72V controller and shipping to Australia. Nothing else was included. He can supply the throttle.
Now I just need to find the right spokes, preferably locally.

I think shipping might have been around $30-$40 and he sells the controllers on ebay for around $35.
 
Gregory,
I recommend you get 13 ga spokes. My original rear wheel was laced by my LBS with 14 ga spokes, and I kept breaking them!
13 ga spokes can be hard to get though, bike shops don't stock them, and don't have the equipment to cut and re-thread them.
If you know, or can work out the length that you require, then send Brett an e-mail from Island Earth Hub Motors, he can definitely get 13 ga spokes in the right length.
That price seems pretty good though. I actually have a spare hub (laced to 20" wheel), I wonder if I can get another motor internals, and make up another bike?
Another project maybe?

On another, totally unrelated issue, I will try and fit my Watts Up meter to my trike, so that I know what the whole system is doing!
 
@Gregory: that was $229 for the MOtor (Bafang Rear-motor) with controller ?
were can you get it for that price ?
(here its more like 600 US$ (with an 50Volt 14A controller))

@Freddy:
thanx for your answers (hope iam not too annoying )

for the shunt: how does it limit current ?
i mean: with an shunt you can measure the current (inderectly, by measuring the the little voltage-drop in the shunt)

ok: the controller knows now, how high the current is...
when it tends to go over a limit (or is over a limit): how does it limit/reduce the current ?

i think by limiting the voltage which goes to the motor (of course not with an resistor like in the old days but by pulsing the electricity running the the motor)
this equals in the effect a lower voltage..

so in my opinion its still this way:
on a steep hill with a controller without amp-limitation (for example my rc-controllers),
low volts of lets say 18Volt
then let us assume, that the current rises up to 15A

on the same hill, with an Bike-controller with amp-limitation,
the same motor would pull on 36V A LOT more current than 15A
when now the current is limited to 15A by the controller
you will not see more power up the hill as with the 18Volt-Setup
infact, the efficience would even be worse (because of the partial-load-condition on the bike-controller), more heat, and a little less power

on the other hand: on flat conditions the 18Volt-setup would be slow, the 36V-Setup fast, more power..
why more power ?
on the flat the 18V setup will pull maybe only 5A
the 36A maybe 10A (not limited by the amp-limit)

meanwhile somebody in the german Bike-forum has second that, he has experienced the same (low and high-voltage on steep hills -> high voltage more heat but not more power)
 
I think you're right, increased voltage = increased speed
increased amps = increased torque.
I put my Watts Up meter on before I went to work.
here are some figures, max amps 14.8A
AHr's used, 1.89
WHr's, 66.6
Max power, ~ 560 Watts
Distance, 6.7 k's.
works out at around 10 WHrs per k, which is not bad for the speeds I'm getting! Potentially means a range of ~ 35 k's on my 10 AHr battery.
If I could limit my speed to 30 kph or less, then my efficiency would improve, and maybe get 40 k's+?
Can't be bothered testing it though, I ride my two wheeled 'bent for longer distances.
 
It was so cheap I jumped at the chance to thrash a cheap bafang.

Just email Keywin ecrazyman@gmail.com for his prices.

I believe the spokes Knuckles used are 216mm for a 26" rim, so I'll start looking around for them soon.
I'll try for 13ga if I can find them.
 
@Freddy:
from today:
14,8Volt battery:
Vorschaubild_MESSUNG_erstesmal%20Burgruine%20_%20Beschriftet.jpg


here bigger, so you can read something:
http://www.kraeuterbutter.at/Bilder2/Radnabenmotor_Vorderreifen/Testlauf%203/MESSUNG_erstesmal%20Burgruine%20_%20Beschriftet.jpg

at over 30% hill i had 25 Amps
i managed to climb this over 30% hill (30m long with gravel - not much gripp ) the first time
when trying it with my two other mountainbikes i always loose grip on the rear-wheel so i didn´t make it up

the help of the front-hub was enough so i managed to climb this very steep hill, also the front-wheel was spinning free some time..
oh: i was doing this with only one arm on the handle-bar because in the other i had my radio-transmitter to throttle gas (Rc-controller and rc-receiver *lol*)

i used only 3,4Ah (14,8Volt-pack) during this 12km ride over 450m of hight (~ 1350feet).. used the motor only to help me on the hill which reach normally from 10% - 20% grades
motor was running 30min
and i made 450meters hight with that

with another battery later (18-20Volt battery) i had peaks up to 40A when going to slow,
so 18-20Volt is too much for the bafang when you have a hilly area and using a controller without current-limitation (which is done by reducing throttle)
 
Gregory said:
It was so cheap I jumped at the chance to thrash a cheap bafang.

Just email Keywin ecrazyman@gmail.com for his prices.

I believe the spokes Knuckles used are 216mm for a 26" rim, so I'll start looking around for them soon.
I'll try for 13ga if I can find them.
Click to expand...
I'm pretty sure I used 228mm spokes.
 
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