How is the 25 km/h limit imposed by controller?

May 14, 2014
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#1
Hi

I got the replacement charger from my supplier earlier this week and I've now bench tested my setup - everything working as it should, thankfully.
I took advantage of the long weekend in Ireland to shorten the motor cable and that's done and tested with only the final insulation to add.

So to my question, the display showed a speed of 42 km/h on the bench. Obviously that's not correct as I have a 20" wheel and the controller is probably set for 28" or something - I haven't changed this yet.
What I can't understand is if the controller thinks the bike is doing 42 km/h, why wasn't the power cut at 25 km/h? That's what I was expecting to be honest.
Also, how do power levels work? I have five. Suppose on level three, should I get 60% power up to 25 km/h or full power up to around 15 km/h? From what I can see, it's a standard sine wave controller.

At least everything looks good now, with the tricky bits done. Looking forward to wiring everything up neatly and trying it for real.

TIA
 

Alan Quay

Esteemed Pedelecer
Dec 4, 2012
2,341
79
Devon
#2
Many controllers have a limit circuit and often it is disconnected by default. Look for two single core cables, often grey or white in colour. Connected is normally the limited state.
 

trex

Esteemed Pedelecer
May 15, 2011
7,703
83
#3
which LCD do you have John? you need to set the correct wheel size for the speedo and limiter to work.
The controller can be programmed to run with internal or external speedometer. If the kit is supplied with an LCD, then it is usually programmed for external speedometer but it's not always the case. The speed is limited by what you set on the LCD but for hub motor, speed is also limited by the motor maximum RPM, typically 15mph for 20" wheels.
 
Last edited:
May 14, 2014
76
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#4
which LCD do you have John? you need to set the correct wheel size for the speedo and limiter to work.
The controller can be programmed to run with internal or external speedometer. If the kit is supplied with an LCD, then it is usually programmed for external speedometer but it's not always the case.
Yes, I know I need to set the wheel size and that will reduce the 42 km/h reading to something more realistic and accurate.
Is it possible so that I don't have a speed limited controller and it will go as fast as it can?
If that's the case, my question about power levels takes on more significance.

Thanks
 

trex

Esteemed Pedelecer
May 15, 2011
7,703
83
#5
yes. You can set the speed limit to 42mph for example, that will derestrict the bike and you can pedal assisted all the way, just set the assist level to 5 if you have 5. You will be then limited by your maximum cadence.
 
May 14, 2014
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#6
yes. You can set the speed limit to 42mph for example, that will derestrict the bike and you can pedal assisted all the way, just set the assist level to 5 if you have 5.
That's interesting. How do you set the speed limit usually? There's nothing about that in the manual.
Forgive my naivety but I thought these yokes were limited by the EU to 25 km/h?
 

trex

Esteemed Pedelecer
May 15, 2011
7,703
83
#7
post a picture of the LCD, I'll post the link to the manual. It's easy to derestrict Chinese kits.
 
May 14, 2014
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#8
Thanks

I've uploaded a pic from their website. It isn't the best but it should be sufficient. I can take a better pic if necessary but it will be tomorrow evening.
You can see there's a separate on/off/level switch.

Details of kit are here

Regards

post a picture of the LCD, I'll post the link to the manual. It's easy to derestrict Chinese kits.
 

Attachments

D

Deleted member 4366

Guest
#9
The LCD looks like the LCD3 from BMSBattery.com. Click the download tab to get the manual and the advanced settings instruction.

http://www.bmsbattery.com/controller/670-s-led770-e-bike-led-meter.html

If it's a Kunteng controller, there's a fair chance that it's switchable between current control and speed control. A normal controller works on speed control, so the PAS levels are target speeds. If you have one that can do current control, they become torque levels.

The maximum speed setting is global, so regardless of PAS level, throttle position or mode setting, speed will be limited.
 
Last edited by a moderator:
May 14, 2014
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#10
That's definitely my display, so thanks for that. It looks like the speed limit defaults to 25 km/h according to the manual but it looks like mine is set higher by default. It's easy to change anyway.

If I use the controller as a speed controller, does that mean that assistance will drop off at a particular speed, depending on the level selected?
If I then get it to work on current control, how exactly does that differ?
Maybe it'll become obvious when I start riding the bike.

I've only ever ridden the Peugeot AE21 and although they were very coy about the specs as it was a prototype, I think it was a torque sensing setup.



The LCD looks like the LCD3 from BMSBattery.com. Click the download tab to get the manual and the advanced settings instruction.

http://www.bmsbattery.com/controller/670-s-led770-e-bike-led-meter.html

If it's a Kunteng controller, there's a fair chance that it's switchable between current control and speed control. A normal controller works on speed control, so the PAS levels are target speeds. If you have one that can do current control, they become torque levels.

The maximum speed setting is global, so regardless of PAS level, throttle position or mode setting, speed will be limited.
 

trex

Esteemed Pedelecer
May 15, 2011
7,703
83
#11
it will be obvious when you start using the bike.
Set the cut off speed to 20mph, that still gives you some protection.
 
D

Deleted member 4366

Guest
#12
You need to play with the settings to see which is best. Not everybody wants the same.
 
May 14, 2014
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#13
Here's a pic of my controller for interest. Any idea if it supports current control?
 

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D

Deleted member 4366

Guest
#14
You'll have to try the settings to see. It's a Kunteng controller, so probably has the setting.
 
May 14, 2014
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#15
Thanks. Will play with it once everything is installed.
 
May 14, 2014
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#16
The controller was set to current control by default. I changed it to speed control just for pig iron and I think the bike is much better.
There seems to be more power in the mid-range and the bike is even easier to ride.
Power tails off completely just after 25 km/h even though I've set the limit higher than that on the controller.
Earlier, I looked up the maximum revs of the supplied motor and coupled with my 20" wheel, it came to just around this speed so I reckon the motor is tapped out.
It's grand though. I can maintain an easy 25-26 km/h in any situation and that's enough for this bike.
 
D

Deleted member 4366

Guest
#17
Another happy chappy!

When you feel you're ready, you need to have a taste of the darker side. I've got loads of spare frog cases if you want to experiment. No cost, but postage would be about a fiver:
 
May 14, 2014
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#18
I could be persuaded. I have a few plans for the winter and I'll talk to you then.

Oscar Wilde had it right - "I can resist anything except temptation."
 
D

Deleted member 4366

Guest
#20
Did you do Kundt's tube at school? We did.
 

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