BPM code puzzle

[wurly]

I'm going to order a BPM hub for my next build, but i'm having a spot of bother determining which code motor to order.
I've just recieved an email from Michael at evassemble which states details of the hubs they stock and sell:
EVassemble
36V BPM is code 10
48V BPM is code 13
Both european legal.

BMSBattery from their website (no code number listed)
36V500W 201rpm
36V500W 393rpm
48V500W 201rpm
48V500W 393rpm

From other places on the www
Code 08 is 393 rpm - 29.80mph(26")
Code 09 is 340 rpm - 25.34mph(26")
Code 10 is 310 rpm
Code 11 is 285 rpm
Code 12 is 230 rpm - (36V)
Code 13
Code 14
Code 15 is 201 rpm

So far this is the information i have managed to get from website and forums.
Now, i realise that rpm will depend on voltage. Anyone running a BPM want to help me decipher this into 'real world' no load rpm?

 

[Scottyf]

I know my code 12 BPM is roughly 230rpm @ 36v
Most have tolerances of 10%

Please remember that as long as they all have the same amount of copper in them they all have the same available power output. But you need to change the current or voltage to match rpm or torque.

The codes are actually winds. So a code 12 is you guess it 12 turns. The more turns the more voltage required for rpm. However the lower the current to achieve the same speed.

Pick a low code for higher rpm. High code for more torque using the same input voltage.

What are you trying to achieve on your build?

 

[wurly]

Thanks Scotty i'll add your info to my list. I'm scouring the ES forum for similar info.

I'm after a reliable replacement setup to replace my current bike which has 36V10ah ping/260rpm Tongxin.
It's going to be a full suspension MTB 48Volt Headway cells and a BPM (or MAC) with a little more mph over what i already have.
I am seeing whats available first and decision will be made from there. The chances are, to begin with, i'll be running at 36Volt and upgrading the pack and controller later.
I don't think the code 10 is going to be high enough rpm, but with 48Volt maybe it will???
I don't understand BMS listings, how both 36V and 48V BPM hubs can give different rpm unless they are different code windings

 

[Scottyf]

You just need to choose what speed you like and then that's it really.

 

[Deleted member 4366]

I have used code 15 (201 rpm), code 11, 12 and I think the other was 13. I tried them all with both 36 and 44v. There's not a lot of difference between them in practice, although there my be some theoretic gain in efficiency by choosing one closely matched to your specific requirements. They can all do 20mph or more. They can all climb any hill. What more do you want? To me 48v is over-kill for these motors: I'm thinking 25-30 mph, but you haven't said what you want to achieve. These motors can make a lot of torque. I've high-sided three times on my rear wheel code 11 at 44v due to the high torque on a surface without grip. Be careful about having too much power unless you want to go for fat moped-like tyres. If you want a bike that's more or less like a normal bike but will climb any hill, and get you along smoothly and efficiently at an average speed of 15mph plus with a reasonable range, a 201 rpm 36v 350w with the 450w controller is perfect. the code 8 (393 rpm) is for 20" or smaller wheels, A code 12 to 15 with the 500w controller at 48v will be drawing 40 amps and have insane torque, which will be difficult to control and give you about 20 mins full power from a massive 48v 20aH battery, which you won't have room for on your bike.
The kits are pretty cheap at the moment, so my advice would be to start with the lower power one first, and if it's not enough, upgrade later.

 

[wurly]

Good info there Dave
Like you have said, torque can be equally as lethal as speed. I'm a bit cautious about buying a hub that is going to 'top out' speedwise, and as they are known as 'hillclimbers' i guess a mid range code will give me the torque i need to go up moderate hills ok.

Here is some reported speed figures from others on ES for the code13

Code 13 is 288 rpm - (21.5mph@48V)(21.6mph@48V)(21-22mph@48V)(18mph@36Volt)
They all seem rather slow to me if they are 288rpm????

A code 10 available from EVAssemble will probably give me the speed i'm aiming for (26-28mph) also and depending on controller and battery pack will give me a fair range (10-12miles).
My Ping pack just doesn't have the necessary C rate, hence me upgrading. And i take your point about going to 48V. It may be possible to build a 12Ah pack to do the job with 12 cells instead of 16 hopefully saving weight and money.

 

[Scottyf]

Ok my two cents on the subject.

I used both the same code 12 motor at 36v and 44v nominal. Using a 450w controller. So that's 10amp continous with a 20amp peak controller.

Now ok at 36v I would travel at 20mph. And up hills I'd slow down to 15mph. But at that speed d only use up 3 or 4amp total hitting peaks of 780watts. This was still plenty and gave a good range.

At 44v I can hit 25mph ish again. I ride up hills at 20mph. But the extra 5mph chews up around 6 to 7amp hours hitting peaks of 960watts. Now the extra speed means I can't put as much effort into the cadence as I could at the lower speed.

Like D8veh said most motors will be around similar speed and bear in mind I'm using 700c wheels or 28inch wheels with 35c tires. But the controller kept the amps down to help extend the range. But the extra speed does eat up alot of battery so please be aware.

Good skills on the high sides d8veh!
Again like I said all the motors have the same theoretical power. But the codes just change volts for amps to achieve the same result.

But in order to help you we really need to know exactly what you want to help advise to the best of our ability. There's plenty of people here that have done the trail and error so you don't have too!

 

[Scottyf]

Also if it's speed your after there's some on endless sphere selling a 1000w conhismotor based in the uk for 170 notes!

 

[wurly]

Hi Scotty
Mmmm...........Direct drive over geared hubs...i'm not too sure!
DD with halls, great for acceleration speed and power consumption. I can see the attraction, however
I have decided that a DD is not what i am going to buy (and i have thought about this quite a lot).
The reason being is, i like having a freewheel, i don't mind pedalling, i also prefer the motor speed reduction you get with geared hub motors, i still believe the Bafangs have a good reliabilty and i would like a fair amount of range. What i am after is something more reliable with a slightly higher speed.
Your code 12 on 44V and 700c wheels is a perfect example of what i am going to try to build, except i'm on 26" wheels and probably 36V.

'Now ok at 36v I would travel at 20mph. And up hills I'd slow down to 15mph. But at that speed d only use up 3 or 4amp total hitting peaks of 780watts. This was still plenty and gave a good range. '

This roughly the performance i get with my set up.

'At 44v I can hit 25mph ish again. I ride up hills at 20mph. But the extra 5mph chews up around 6 to 7amp hours hitting peaks of 960watts. Now the extra speed means I can't put as much effort into the cadence as I could at the lower speed. '

Thats what i would expect which is why i am budgeting for a new battery pack.

I am going to get a code 10 from evassemble, i have bought parts from there before and have no problems. Ok it's probably designed for smaller wheels (so is my 260rpm tongxin). With this hub and higher C rate 36Volt pack, i should be near to my desired speed/range. I can try it out on a spare 36V controller and my Ping pack. If i need more Volts/power i can a build a pack to 48V instead of 36Volt. A new battery pack has always been on the cards.
Incidently, this is a reply i just recieved from BMSBattery
RPM201 , it is code 17 .
RPM393, it is code 8 or 10
So.....they are as equally confused as i am.

Any thoughts?

 

[Deleted member 4366]

My 201rpm is code 15. Last time I tried to order from EVassemble they couldn't build the motor into a wheel and I was blanked on a lot of e-mails after I got the final price. BMSbattery are a lot more reliable in that respect, except that they have a nasty habit of demanding more money for postage when your order is ready to ship. $44 last time! So, if you want it in a wheel, it might have to be the code 15 201rpm, A thing to remember. If your average speed will be 15mph, a code 15 will use a lot less battery than a code 10 due to efficiencies. A code 10 will have optimum efficiency at over 20mph, which you probably won't be doing most of the time. Personally, I wouldn't go higher than a code 11.

 

[wurly]

I am going to lace the motor myself Dave. I have done 3 or 4 now, i don't find it that tricky although i've yet to lace a rear wheel with an offset.
The problem is, where to get a code 11 or 12. Looking at the speeds reported by others for code 13 even at 48V! it isn't reaching the speeds i want.
With my 260rpm Tongxin, i can easily acheive speeds of 18mph drawing around 3-4A. Obviously, that is with a lot of pedalling. I guess you could say that motor isn't running at optimum efficiency either yet i can get 20+miles out of 10Ah's.
I should also say, i have my 'add on' current limiter where i can set a threshold that clamps throttle voltage when current is too high. This gadget takes away the worry of exceeding the discharge rate of my pings.
I can alter the circuitry for a higher C rate pack, so the inefficiencies of running the code 10 at lower rpm (not forgetting my assistance of pedalling) shouldn't waste too much power. At speeds over 20mph the code 10 should be nearing it's efficient speed, although i realise current will increase as my pedalling power decreases. If that makes sense?
But yes, a code 11 or 12 would probaly be ideal. It's a shame no-one sells one.

 

[Scottyf]

I didn't get a chic with my bpm from Bms they just sent through a code 12. I just said I'd like around 23 mph at 36v. Which was probably about right in a 700c wheel no load speed.
I would have liked it to be slightly quicker.

But the motor is hideously torquey anyway and doesn't slow down much on hills at all.

Today I really went for it and managed to use up 2.7amp hr on the 10.5mile to work. The lowest I've ever got it. But I had to pedal like a maniac to make the efficiency better.

The motors on the winds appear to go down in 20rpm per chosen wind. If you got for the lower wind code then you can make up the torque by feeding in more current.

If you got got a higher wind or more turns you can make up up speed with volts. Both have there pitfalls.
Current usually means alot of heat. Increase in volts mean higher quality controllers and components while possibly having issues on smooth starts and control.

 

[wurly]

Exactly Scotty both have pitfalls. I kinda decided a few days ago i want a code 10. What the hell it's all cheap fun......(well it is compared to my other hobbies)

I'll close this now. Thanks to you both for your thoughts, it's much appreciated.