Stuck at a very low speed, where is the problem?

[AMC11]

I’ve been lurking here for a while, can I just take the opportunity to thank everyone for what a fantastic resource this forum is, I’ve learned so much here. Now it’s time for me to ask for help with a stubborn problem.

In brief, I’ve got a combination of front geared hub motor, controller and 48V battery (12S lipo) that tops out at around 11mph and refuses to go any faster (also apologies for mph in general, the UK is apparently a metric country, except where it isn’t. What with all the road signs and local regulations being in mph I’m kind of stuck with it). My own investigations lead me to believe I’ve been unlucky and bought an incredibly slowly wound motor since the problem doesn’t seem to be controller or battery related. Before I go ordering another motor I’d like to see if there’s anything I’ve missed.

The hub motor I bought is listed here. It’s a good price and I figured a lot of these 250W hubs are similar so I’d be fine with it. Note it’s a 36V motor which makes me surprised it runs so slowly even on 48V. I’m currently using it with a sensored controller (from here) although I tried a sensorless controller and had exactly the same top speed. That should rule out any issues with the hall sensors I assume. The controller is connected to one of those basic LED (not LCD) displays and I’ve also tried shorting the controller on directly with no change in the speed either. I’ve tried both twist-throttle and PAS sensor and both work but neither changes the top speed. Batteries are two 6S 16AH lipos in series, I’ve used lipos for a few years in RC so I’m pretty familiar with them.

So that’s about the extent of it. With the bike up in a stand and the wheel running off the ground the max speed is about 11.5mph, I measured the voltage across the phase wires with a multimeter on AC mode and see about 48V if that’s of any use. Current consumption with no load is minimal. The motor runs smoothly and quietly with plenty of torque on hills, there’s certainly no shortage of power, only speed. The wheel is installed in a rigid steel fork with a torque arm, my aim with the conversion was more about pedal-assist for hills/headwinds with the emphasis on range rather than outright speed or power.

 

[Paladin]

Some of the controllers are set up for a 3-speed switch.
If you don't have the 3-way and don't have it directly wired it will only run at half speed.
Green to black wires connected for full power, on this example. Others maybe different.

 

[nutnspecial]

Hi Op, what battery are you running? The controller post/ad is confusing because it only allows a 48v selection but says in details it's '36v'. As Paladin says the three spd switch is a good possibility (of limited controller function without), but the controller doesn't even appear to be wired for a spd switch. Other than that I have no clue- never heard of a wind that slow.

 

[flangefrog]

The controller you are using allows different "assist levels" to be set using an lcd or led display. These limit the speed (more accurately, the pulse width I think) like what you're seeing. There's an option for it to start up at a certain assist level or remember the last assist level.

You will probably need to buy a display or use an arduino/usb to serial adapter or similar to set the correct assist level.

The cheapest display you can buy is this one: http://www.aliexpress.com/item/24V-36V-48V-Electric-Bicycle-KT-LED-890-Control-Panel-Display-Electric-Bike-Parts/32613417275.html?spm=2114.13010208.99999999.367.xaa0MP
You won't be able to use it to set which assist level the controller starts up in, so if you want to use the controller without a display and the controller is set to start up in a specific assist level (and not to remember the last level) you will need an LCD to program it.

Here are two of the LCD models:
http://www.aliexpress.com/store/product/ebike-24V-36V-48V-intelligent-black-KT-LCD5-Control-Panel-LCD-Display-Electric-Bicycle-bike-Parts/1314442_32613514881.html
http://www.aliexpress.com/store/product/ebike-24V-36V-48V-intelligent-LCD-Control-Panel-LCD-Display-Electric-Bicycle-bike-Parts-for-KT/1314442_32613010219.html

Edit: sorry, I didn't read properly and I see you already have an LED display. The controllers do allow a speed limit (and wheel size, speed sensor settings etc) to be set using an LCD, so it could still be something that can be fixed with an LCD.

 

[d8veh]

That controller doesn't work properly without a LCD. You get restricted speed without one. Do you have a LCD?

 

[Paladin]

I need to stop trying to be helpful, guess I am bad at it.

I missed the controller link...

It says in the sale..."Check out our LCD screen version which allows you to toggle between unrestricted and restricted modes to give you the best of both worlds and totally road legal (when set to 15mph limited mode on roads)."

Sounds like its in restricted mode. edit...not restricted. I will just shut up now.

 

[AMC11]

The plot thickens.

I recall that I got in touch with Panda Bikes (the sellers of the controller) before buying it to ask about the speed restriction. I planned to keep within the UK law which states 15mph top speed (plus a small tolerance). Here's what they said:

-Their controllers are unrestricted by default, also says this on the eBay page
-They have a 'special' LED display that limits the controller to 15mph, this is the one I ordered and what is currently connected. I can't get a photo at the moment, but it's the simple display with only a power and mode button, with three pedal assist levels.
-If I disconnect the display completely and turn the controller on by shorting two of the display connector wires together, there is no change in the top speed at all.

Is it possible the 15mph restriction is miscalibrated and the controller remembers that even with the display disconnected?

I'm not keen on the LCD display since it would be a chore to fit on my bars. According to what Panda bikes told me I should be restricted to 15mph with their display, obviously something has gone wrong here. If the controller has been stuck in some restricted mode is the LCD the only way to undo it?

One last thing - I tested the wheel out with a sensor less controller also from Panda however I did not connect the display to it, I shorted it on directly. Still I had the same top speed even with that supposedly unrestricted controller.

Would it be worth me ordering a replacement LED display (not from Panda in case the fault lies there) before I go for the LCD one? Much cheaper and more compact.

Ugh. This whole thing had been a headache, I had pretty low requirements, 15mph top speed would have been just fine. At 11 the assistance is pretty close to useless except on steep hills.

Edit. By the way, very misleading of Panda to say you can stay legal with a display that let's you change the speed restriction on a whim. That is explicitly as illegal as no restriction at all under the current law. I'all dig up the source later but anyone telling you 'off road' switches are road legal in the UK is either misinformed or lying.

 

[flangefrog]

The controller can only know the speed of the bike if it knows your wheel size and pulses/revolution of your speed sensor. If this information wasn't given when you bought the display then it might not be correct.

Your current display can be reprogrammed by buying an LCD display and performing a copy of the settings from the LCD to the LED display.

 

[d8veh]

That's right. You need the LCD to enter all the settings.

"I'm not keen on the LCD display since it would be a chore to fit on my bars."

The S-LCD5 from BMSBattery is the same size and fitting as the panel that you have. What's the problem?

 

[AMC11]

That's right. You need the LCD to enter all the settings.
The S-LCD5 from BMSBattery is the same size and fitting as the panel that you have. What's the problem?

Ah right, thanks for that. I done a quick search for LCD displays and only seemed to find those huge ones. If that one is compatible with my controller I'll go and order it.

One last thing though - I done a quick test with the wheel using an electronic speed controller I normally use for RC brushless motors, no speed restriction on that. [strike]Running on 3S (12V) the wheel turned really slowly, so much so I had trouble measuring the speed (had to time revolutions and calculate it via wheel radius). The unloaded speed should be roughly proportional to voltage correct? So the fact it was barely scraping 2-3mph on 12V, suggests the winding really is slow enough to only be getting ~11mph on 48V? I'm going to retest on 4S (16V) since I don't think I have any other controllers that support a higher voltage.[/strike]

Ignore the above. I think these RC ESCs can have trouble with hub motors, but I found one that could drive the wheel at 8mph on 16V. That implies a top speed of 24mph on 48v which seems perfectly reasonable. Definitely not the motor winding that's the problem then.

 

[AMC11]

Problem solved with an LCD (KT LCD03). Could have avoided a whole load of annoyance by getting one from the start, rather than cheaping out with the LED display, cost me more in the long term. There's a lesson for the ages. Nice to end the wild goose chase on what was the problem at least.

So it's possible to copy the LCD settings to the LED display right? I was looking in the instructions (page 36) but I'm not sure how to interpret the wiring connection. I thought you would connect the wires between the LCD and LED like for like by color, instructions seem to be saying I change the order? Really not clear from studying it.

 

[flangefrog]

The black and red wires go straight through and the yellow and green (rx and tx) are switched. You can also buy a copy cable here: https://www.aliexpress.com/store/product/Copy-Wire-for-KT-Series-Display-Meter/1314442_32615771989.html

 

[AMC11]

The black and red wires go straight through and the yellow and green (rx and tx) are switched.

OK I connected the LCD to the LED like this. I also set C11 to 2 as that sets the LCD as the data source to copy to other meters (well that's what I gathered from the instructions, the english is....less than perfect). Tried what was in the instructions but couldn't get a 'copy' confirmation message no matter what. LED meter settings remain unchanged when I plugged it into the controller. Not the end of the world, I can deal with fitting the LCD on.

Edit: The copy confirmation only appears on the device being copied to, apparently.

 

[dsm1991]

Hey guys sorry to butt in, but I have the exact same problem but I chose to order a LED display with 5 PAS levels. The part hasn't arrived yet but will that solve the problem as well? Or likely won't matter because the controller is programmed for 1-3 pas? Should I just return the part now and pick up the same LCD (KT LCD03)? Also my original led display is destroyed, so I don't have one to copy from. What do I do then? Don't they have a smart lcd that can program it self? Not sure what to do now really. I guess I could try to order the exact model from the owners manual. Funny how the one shown here is not the one that came with the bike when I bought it....fairly certain the guy just took it for a different bike or something. But here's the manual attached, if anyone can tell me what display that is or what I need to do here to get full speed again, would be much appreciated! Thanks.
Oh and the display that was destroyed was a 48v 810 display. If that matters, thought it was weird that it wasn't a 36v, which the bike motor and battery and controller are 36v, but I bought a 36v display unfortunately they sent a 790 and the wire thickness is different but when I wired it up I only get reduced speed. So little bit off putting there. Very confused.

 

[docw009]

dsm1991, you can always jump in, but I think it's better to start a new topic like "Ebike too slow with mew display". People see a topic that was started several years ago, they ignore it.

OK, I'll comment. Your user manual doesn't show a KT controller, so no KT displays can work with it. You need to have a KT controller to work with a KT display,

Then you mentioned that you broke an 810 display. Was that this 810LED? It comes in several versions. The four wire version is analog and is either 24,26, or 48V. It also requires a specific controller to work with it, and that is not a KT controller. There is also a five wire version which is digital and that will not work with the controller that runs with the 4 wire displays. Finally, they sell the four wire version with a five pin lug, but the fifth pin is not connected.. I don't know why they do that. If you put this 5 wire version on a dudgital controller, it woon't work irght either.


In any case, you have to buy the right display to match your controller.

 

[amberwolf]

Hey guys sorry to butt in, but I have the exact same problem but I chose to order a LED display with 5 PAS levels.

Which controller do you have? You'll need a display that is made to be compatible with that specific controller, or they won't "understand" each other.

Usually (but not always) a display that appears to be identical, same model number, etc., as the original will work, but this isn't always true either, because some displays are programmed with firmware for a different system even though they look the same. That's more common with OEM systems (brand name bikes, etc) because they often use customized firmware; if so the generic ones don't work with them. (or work but have different menus and settings and responses)