Hi, I have an electric mtb with 250w (or so I think) rear hub motor. My LCD is an JS, and I tried to change the wheel size (P06), the speed limit for PAS (P08) up to 100 but with no success. The P14 - current limiting of controller- is missing from lcd. Skips over it. Is there a way to get over the 25km/h limit? If I lift the bike and use throttle it goes more than 25. I don't know if the limit is the rpm or how it reads speed. I attach pics of the controller, opened up, and from lcd. I must confess that I have no electric knowledge but I just want to know if I can get past limitation or if I need to buy a different controller and display what to shop for. Thank you very much in advance.
Speed removal 250w rear hub
- Thread starter TheAnto
- Start date
Hub motors a built for a certain speed. To make it go faster you need to increase the voltage from 36 to 48v.
Right, I have one of those controllers. On mine, the brown wires are to reverse the motor rotation direction, but all they are is a jumper to make a CPU input high or low, so if yours has different software in it, it could be used for anything. It's worth checking whether connecting them reverses the motor or whether it controls the speed limit.
First, you need to establish whether the controller is limiting your motor speed. You have to lift the wheel off the ground and spin it up to maximum by using the throttle or the pedal assist in bottom gear. sometimes, without load, the speed restriction will overshoot before it cuts off, so use a tiny bit of brake to put the smallest load on it. You must measure the speed fairly accurately. You can use the LCD or a cycle computer.
You must measure the speed with a fully charged battery and then again with a well-drained battery. If there is no restriction, there will be two different speeds that are in direct proportion to the battery voltage. If there's a restriction, they'll be the same. It's normally obvious when there's a speed restriction when you test because you can see/feel the motor cutting in and out.
The wires are hidden in all your photos, but it looks like you have no white wire in your motor cable. That means that your speed will go to zero whenever you freewheel. You can get round that by adding your own speed sensor. Get one of those £2 cycle computers from Ebay or an old one that you have lying around, and cut off the display head. Install the sensor and wheel magnet as normal. There are two wires in the cable. Connect one to the white wire in the motor connector and the other to any 5V one (red in the throttle, pedal sensor or motor cable). It's a while since I did it, but you might have to connect to a black wire instead of red. No harm will come if you get that wrong, but it'll only work one way depending whether there's a pull-up or pull-down resistor in the controller. I think there's a setting in the controller for the number of magnets in the speed sensor, so you have to set it to one when you have the external sensor.
Please let us know whether or not your speed is restricted after the test.
First, you need to establish whether the controller is limiting your motor speed. You have to lift the wheel off the ground and spin it up to maximum by using the throttle or the pedal assist in bottom gear. sometimes, without load, the speed restriction will overshoot before it cuts off, so use a tiny bit of brake to put the smallest load on it. You must measure the speed fairly accurately. You can use the LCD or a cycle computer.
You must measure the speed with a fully charged battery and then again with a well-drained battery. If there is no restriction, there will be two different speeds that are in direct proportion to the battery voltage. If there's a restriction, they'll be the same. It's normally obvious when there's a speed restriction when you test because you can see/feel the motor cutting in and out.
The wires are hidden in all your photos, but it looks like you have no white wire in your motor cable. That means that your speed will go to zero whenever you freewheel. You can get round that by adding your own speed sensor. Get one of those £2 cycle computers from Ebay or an old one that you have lying around, and cut off the display head. Install the sensor and wheel magnet as normal. There are two wires in the cable. Connect one to the white wire in the motor connector and the other to any 5V one (red in the throttle, pedal sensor or motor cable). It's a while since I did it, but you might have to connect to a black wire instead of red. No harm will come if you get that wrong, but it'll only work one way depending whether there's a pull-up or pull-down resistor in the controller. I think there's a setting in the controller for the number of magnets in the speed sensor, so you have to set it to one when you have the external sensor.
Please let us know whether or not your speed is restricted after the test.
Vfr400 clearly knows this controller and given you some v useful info.
If you discover the controller is restricting the speed then a new controller may give to a littlemore speed.
I had a bafang 250 w hub from 8fun.uk that did 15 mph reducing to 10 as battery depeleted.
A ku65 controller from bms battery gave it another few mph. Max 18mph hot but still Ing to 17 quite quickly
in the end I added a booster battery. This is done by cutting the power lead at an appropriate point and soldering a connector in. I like xt60 connectors. You can then add in lipo bricks or home built packs using 18650 cells . Lipo come with risks and hassle.
Just about all.36v controllers inmy.expeience will cope with a 7. 4v booster, many with a 11.1v and a few with more without going pop. You get a speed and torque increase accordingly
all comes with a big health warning as it pushes the capabilities of both the motor (which might fry or melt nylon gears and windings) And controllers (Can blow either the capacitors or the mosfets )
I still have a bike setup this way but it is nearly always used without a booster. Occasionally I stick a 11.1v on. it to get 48v. It's a Woosh xf07 with a small controller built into the battery rail. On my 700c hybrid this will do 24mph got settling to 22mph. At 36v it does 16mph
If you discover the controller is restricting the speed then a new controller may give to a littlemore speed.
I had a bafang 250 w hub from 8fun.uk that did 15 mph reducing to 10 as battery depeleted.
A ku65 controller from bms battery gave it another few mph. Max 18mph hot but still Ing to 17 quite quickly
in the end I added a booster battery. This is done by cutting the power lead at an appropriate point and soldering a connector in. I like xt60 connectors. You can then add in lipo bricks or home built packs using 18650 cells . Lipo come with risks and hassle.
Just about all.36v controllers inmy.expeience will cope with a 7. 4v booster, many with a 11.1v and a few with more without going pop. You get a speed and torque increase accordingly
all comes with a big health warning as it pushes the capabilities of both the motor (which might fry or melt nylon gears and windings) And controllers (Can blow either the capacitors or the mosfets )
I still have a bike setup this way but it is nearly always used without a booster. Occasionally I stick a 11.1v on. it to get 48v. It's a Woosh xf07 with a small controller built into the battery rail. On my 700c hybrid this will do 24mph got settling to 22mph. At 36v it does 16mph
Thank you very much for your elaborated answers. I've managed to do the fist step of your suggestions and I depleted the battery in order to compare. The speed decreases as the battery gets empty. It's a variation of 3-4 km. What seems very odd is that If I lift the back wheel and use throttle it goes to the same speed as if I spin the crank with peddal assist, no matter how hard I spin it. I cannot get the speed over 27 km.
The second part I have tried, I got a cycle computer, installed the magnet and sensor, test it and displayed roughly the same speed as the bike lcd. After I removed the display of the cyclecomputer I didn't managed to make it work. I looked for the white wire in the motor connector as you said, but I couldn't find it. I switched the magnets to one, tryed to connect the 2 cables various ways but with no success. Indeed my display does not indicate speed when the motor is not engaged by throttle or by pas. Should my next step consist in buying a new controller and display? If so, do you have any recommendations? I can find versions not restricted or maybe easier to fix? With a known and proven method? And maybe one that can manage easily a bigger voltage battery in case it comes to that as a final solution? The one with changing even the motor for a more powerful one I'm not considering. Too much of a hassle for my knowledge at the moment. Thank you very much.
The second part I have tried, I got a cycle computer, installed the magnet and sensor, test it and displayed roughly the same speed as the bike lcd. After I removed the display of the cyclecomputer I didn't managed to make it work. I looked for the white wire in the motor connector as you said, but I couldn't find it. I switched the magnets to one, tryed to connect the 2 cables various ways but with no success. Indeed my display does not indicate speed when the motor is not engaged by throttle or by pas. Should my next step consist in buying a new controller and display? If so, do you have any recommendations? I can find versions not restricted or maybe easier to fix? With a known and proven method? And maybe one that can manage easily a bigger voltage battery in case it comes to that as a final solution? The one with changing even the motor for a more powerful one I'm not considering. Too much of a hassle for my knowledge at the moment. Thank you very much.
Each motor type has a specific number of RPM it can run at, many common hub motors spin at about 260-270 RPM @ 36v. Unloaded (wheel off the ground) speed for that type of motor is about 32-33 kph so that you end up with a top loaded speed of around 25 kph.
Your 27 kph motor is a little bit slower than that so it may be a motor designed for more hill climbing power. The motor experts here need to see the numbers engraved on the motor casing to be able to tell you if it is a slow wind motor or not.
HI. That 27kph was on an almost depleted battery. With fully charged baterry I get 31kph with the wheel off ground. That means that the motor cannot deliver more power no matter what I do? I will try to remove the rear wheel and to try and get a look at the motor one of this days.
Don't confuse motor speed and power.
My Mxus XF08 will climb 13% hills at 24 kph, that is power (I help it a little by being in the correct gear and giving a bit of welly). On the flat with no wind it peaks at 27 kph give or take a whisker, that is it's top speed. I can pedal over and beyond that top speed (but not to infinity...
).If I run it at 48v (still using a 15 Amp controller) it should reach about 36 kph. It will probably not climb any faster however, for that I would possibly need to use a 17 Amp controller.
Going over and beyond those above limits would probably lead to stripped nylon gears or even worse, melting of wire insulation and motor failure because of excess heat. Once you get out of your motors 80% efficiency/comfort zone things can get a bit toasty...
You don't need to take the motor apart to see what's inside. You can find loads of pictures and videos with Google.