Secret of panasonic hub climbing power

[1boris]

I have not tried the Panasonic hub motor in Ktm erace p.But from what I read it is the best legal"250w" ebike when it comes to hill climbing.and it is a hub motor.Why?
I would love to get D8vehs opinion but I belive it is easy.And it can even be improved
I belive it is as simple as a hubmotor winded for 150 rpm at 36v running at 48 volt.(in runner)
If that is correct a larger bafang cst (outruner) winded for 150 rpm at 36v running at 48 volt should be stronger?
Only bad thing,they can not be derestricted to go faster at 48 volt

 

[Deleted member 4366]

If you take an average 20mph Bafang SWX and run it at 48v, it'll climb pretty well too, but then its speed goes up as well, and, as you know, efficiency goes down when its running at less than half of its max speed, so increasing voltage normally makes efficiency suffer.

If the motor was wound for 15mph at 48v, it would be efficient right down to 7.5 mph. Even at 4.5mph it would still have an efficiency of 55%, so at 15 amps, it would have an output power of 400w.

Compare that with the Bafang SWX wound for the normal 20 mph. It's efficiency will only be 45% at 4.5 mph, so at 15 amps and 36v, its output power would be 243w - nearly half as much. If you ran it at 48v, it's efficiency at 4.5 mph would be only 40%, so output power at 15 amps would be 288w.

I don't know the actual winding speed of the Panasonic hub-motor, but we can see how output power is affected by winding speed, by voltage directly and the negative effect of efficiency:

20mph Bafang at 15A 36V 4.5 mph: 243w 45% efficiency
20mph Bafang at 15A 48v 4.5 mph: 288w 40% efficiency
15 mph 48v motor at 15A 4.5 mph: 400w 55% efficiency
Xiongda in low gear at 36v 15A 4.5mph: 324w 60% efficiency

 

[trex]

the TCM in the Zephyr CDN still has about 70% efficiency at 4.5mph, 36V, 14A (352W). The new version of the TCM will take 20A.

 

[Kudoscycles]

If you take an average 20mph Bafang SWX and run it at 48v, it'll climb pretty well too, but then its speed goes up as well, and, as you know, efficiency goes down when its running at less than half of its max speed, so increasing voltage normally makes efficiency suffer.

If the motor was wound for 15mph at 48v, it would be efficient right down to 7.5 mph. Even at 4.5mph it would still have an efficiency of 55%, so at 15 amps, it would have an output power of 400w.

Compare that with the Bafang SWX wound for the normal 20 mph. It's efficiency will only be 45% at 4.5 mph, so at 15 amps and 36v, its output power would be 243w - nearly half as much. If you ran it at 48v, it's efficiency at 4.5 mph would be only 40%, so output power at 15 amps would be 288w.

I don't know the actual winding speed of the Panasonic hub-motor, but we can see how output power is affected by winding speed, by voltage directly and the negative effect of efficiency:

20mph Bafang at 15A 36V 4.5 mph: 243w 45% efficiency
20mph Bafang at 15A 48v 4.5 mph: 288w 40% efficiency
15 mph 48v motor at 15A 4.5 mph: 400w 55% efficiency
Xiongda in low gear at 36v 15A 4.5mph: 324w 60% efficiency

Electric Dave (D8veh)
....On Mastermind ......and my specialist subject is Bafang hub motors produced from 2009 to 2014.....wow!
I am impressed
KudosDave

 

[JohnCade]

Electric Dave (D8veh)
....On Mastermind ......and my specialist subject is Bafang hub motors produced from 2009 to 2014.....wow!
I am impressed
KudosDave

Doesn't he teach electronics or something? So sarcasm aside he should know stuff like this shouldn't he?

 

[flecc]

I think he's just guessing.
.

 

[oldtom]

In my previous existence as an engineer before discovering the joys of not actually working, I always understood from from older engineering sages that, 'Those who can, do; and those that can't, teach!'

My other half, a maths guru/teacher/lecturer relates a similar worldly observation from her sphere of activity: 'Those who can, teach; those who can't, manage!'

I imagine such slurs occur in many other occupations too.

Tom

 

[Deleted member 4366]

I imagine such slurs occur in many other occupations too.

Tom

Yes, like the poor OAPs suffering from dementia that have delusions that cause a warped sense of reality.

 

[1boris]

Are you still happy with your xiongda motor d8veh?
I was thinking about buing one some months ago but ended up with a mac 12 kit.But now I want something new again.The mac 12 is not very stealth imo.To massive.But climbing ability is better than my bafang bbs 500w.
I want something legal so it will be a 250w bafang bbs or a xiongda kit

 

[Croxden]

Those than can do... Those that can't teach... If you can't teach, take PE.

 

[Deleted member 4366]

Are you still happy with your xiongda motor d8veh?
I was thinking about buing one some months ago but ended up with a mac 12 kit.But now I want something new again.The mac 12 is not very stealth imo.To massive.But climbing ability is better than my bafang bbs 500w.
I want something legal so it will be a 250w bafang bbs or a xiongda kit

I've done about 300 miles on it now, and it's my main bike. I use it for just about everything. When I'm on my own, it's very good, but when I ride with a friend, who has a 500w BPM, hills seem a bit of a chore. I have to change down into low gear and go up slowly, while he just cruises up them. We put in the same effort, but it takes a lot longer with the Xiongda.

The Xiongda is halfway between a crank-drive and a normal hub-motor. You have to use the gears a lot more. I go right down to first sometimes on the small front cog - say for a 30% hill. On normal hills - say 15% - I only have to go to first gear, but on the big front cog. Don't forget that I'm 100kg and often carrying heavy shopping too.

If you want legal, then the Xiongda is a good solution. It should be even better now with the new sine-wave controllers. I would say that in standard form it's got about the same climbing power as a Bafang BBS01. I soldered the shunt in mine up to 20A, so it goes a bit better.

In summary, everything has advantages and disadvantages. The Bafang is a real quality product. The Xiongda feels a bit rough around the edges, but has so far proven to be reliable.

 

[1boris]

Thanks for the reply.I think I will go for the Xiongda.It is more exiting than another bafang bbs.But I agree the bafang is a very nice product.

 

[trex]

no, it's not Boris. The xiongda requires a specially programmed controller and a 3-way switch, you are stuck with a kit from xiongda. If anything goes wrong in the future, you'll be stuck without much support.
If you want a legal kit, BBS01 is the way to go.

 

[1boris]

If you take an average 20mph Bafang SWX and run it at 48v, it'll climb pretty well too, but then its speed goes up as well, and, as you know, efficiency goes down when its running at less than half of its max speed, so increasing voltage normally makes efficiency suffer.

If the motor was wound for 15mph at 48v, it would be efficient right down to 7.5 mph. Even at 4.5mph it would still have an efficiency of 55%, so at 15 amps, it would have an output power of 400w.

Compare that with the Bafang SWX wound for the normal 20 mph. It's efficiency will only be 45% at 4.5 mph, so at 15 amps and 36v, its output power would be 243w - nearly half as much. If you ran it at 48v, it's efficiency at 4.5 mph would be only 40%, so output power at 15 amps would be 288w.

I don't know the actual winding speed of the Panasonic hub-motor, but we can see how output power is affected by winding speed, by voltage directly and the negative effect of efficiency:

20mph Bafang at 15A 36V 4.5 mph: 243w 45% efficiency
20mph Bafang at 15A 48v 4.5 mph: 288w 40% efficiency
15 mph 48v motor at 15A 4.5 mph: 400w 55% efficiency
Xiongda in low gear at 36v 15A 4.5mph: 324w 60% efficiency

Thanks for taking time to explain again
I understand effiency the way you explain it.But I get confused when I look at ebike ca simulator.If I for example use the cst motor in two diffrent setups on the simulator.one setup is 36volt 20 amp=720w (cst) the next is 48v 15 amp=720 (cst).The simulator shows the same effiency.So it is better running at 48 volt because you get more speed.Why is effiency the same in this simulator?

 

[Deleted member 4366]

Yes, that's what the simulator shows, which sort of makes sense, but I'm not convinced that it reflects all the factors that you get in a practical situation. In theory it makes no difference whether the pulses from the controller are high and narrow or shorter and wider - the height being the voltage and the width the current. As RPM increase, so does the back emf, which will cancel out the supplied voltage at max RPM. If you have higher voltage, that'll happen at higher RPM, so your motor will be able to run faster.

 

[hoppy]

the TCM in the Zephyr CDN still has about 70% efficiency at 4.5mph, 36V, 14A (352W). The new version of the TCM will take 20A.

Crank drives have the great advantage of being able to run the motor at or near its peak efficiency at any road speed simply by selecting the best gear ratio.

 

[derf]

I've done about 300 miles on it now, and it's my main bike. I use it for just about everything. When I'm on my own, it's very good, but when I ride with a friend, who has a 500w BPM, hills seem a bit of a chore. I have to change down into low gear and go up slowly, while he just cruises up them. We put in the same effort, but it takes a lot longer with the Xiongda.

The Xiongda is halfway between a crank-drive and a normal hub-motor. You have to use the gears a lot more. I go right down to first sometimes on the small front cog - say for a 30% hill. On normal hills - say 15% - I only have to go to first gear, but on the big front cog. Don't forget that I'm 100kg and often carrying heavy shopping too.

If you want legal, then the Xiongda is a good solution. It should be even better now with the new sine-wave controllers. I would say that in standard form it's got about the same climbing power as a Bafang BBS01. I soldered the shunt in mine up to 20A, so it goes a bit better.

In summary, everything has advantages and disadvantages. The Bafang is a real quality product. The Xiongda feels a bit rough around the edges, but has so far proven to be reliable.

that perversely please me, I'm getting a bafang 500w bpm soon!

 

[derf]

that perversely please me, I'm getting a bafang 500w bpm soon!

thanks for all the detailed practical info (I thought about putting the 328 rpm bpm in a 26 wheel, but gathered efficiency would be too low in normal use)..

 

[Deleted member 4366]

Crank drives have the great advantage of being able to run the motor at or near its peak efficiency.........

That's true, but nobody rides them like that so you get the same efficiency as hub-motors.

 

[cwah]

I think the main benefit of a cran drive is to be able to assist you at any speed.

With xiondga it goes to 17mph max and that's it.

It's good to go slow and for slopes... but for city riding it's not always the best when we have nice straight road where we could spin at 25mph on foot itself!