Ebike conversion kit

Marione

New Member
Hi everyone I have a 20inch tern d8 folding bike which I converted with this kit

Jacksking Bicycle Conversion Kit, 36V/48V 250W Motor KT900S LED Display 20” Wheel E-bike Conversion Kits Rear or Front Waterproof Electric Bicycle Conversion Kit(48 V Rear Motor): Amazon.co.uk: Sports & Outdoors
Shop Jacksking Bicycle Conversion Kit, 36V/48V 250W Motor KT900S LED Display 20” Wheel E-bike Conversion Kits Rear or Front Waterproof Electric Bicycle Conversion Kit(48 V Rear Motor). Free delivery and returns on all eligible orders.
www.amazon.co.uk

And a 48v 12.5ah Hailong battery

I am obviously trying to find a solution to increase the speed as I dont believe it makes the 25km/h that it should.
Unfortunately it doesn't have a speed sensor at the wheel so not sure how it check the actual speed.
Any idea?
Mario
 

Sierratim

Well-Known Member
You can use a smartphone app to get speed readings, though I'm not familiar enough with these to know which, if any, will give you real time vs average speed. I use mine to track position and distance on its mapping function. Handlebar mounting to read real-time speed can be a bit of a challenge at times.

There are any number of simple handlebar-mounted 'bike computers' that you can add to track speed. The ones that rely on a magnet attached to a spoke range from maybe $10US and up. A fork-mounted sensor detects the magnet spinning by. By inputting your wheel/tire circumference the computer calculates speed and distance. The computers are available with wired sensors (lower $) or wireless sensors (higher $). We use Sigma bike computers on our mech bikes. Moderately priced and reliable.

GPS units are more $ but add more features (mapping, etc) and don't require a magnet or sensor. Most come with handlebar mounts.
 

Marione

New Member
Thanks for this info.
I saw few video on youtube where they trick the speed sensor in order to make the bike a bit quicker. I was wondering if i could do the same with my kit.
 

Sierratim

Well-Known Member
I don't have direct experience with these, but I believe they rely on a converter that is wired between the controller and whatever sensor is used to detect bike speed. The converter takes the incoming speed signal and divides it down, often by 2x making the controller think the bike is going 1/2 its actual speed. You mentioned that the bike doesn't have a speed sensor at the wheel. For a speed limiter to work there must be one somewhere, perhaps in the drive motor itself? This would make it harder to wire in a converter to fool the controller.
 

Marione

New Member
I believe is in the motor. I dont see anything that look like it anywhere. The bike works also without the pedal assisted sensor and makes more or less the same speed. The most annoying thing is that if i want to cycle faster the motor seem to brake me from doing it
 

Sierratim

Well-Known Member
I'm guessing what you're feeling is the motor drag when the speed limiter cuts in. When power is cut to the motor you need to add enough power to the system to make the hub-mounted motor spin. Judging by the diameter of the motor I'm guessing its a geared motor which will add more drag than a direct drive motor, hence the feeling of braking.
 

indianajo

Well-Known Member
I'm guessing what you're feeling is the motor drag when the speed limiter cuts in. When power is cut to the motor you need to add enough power to the system to make the hub-mounted motor spin. Judging by the diameter of the motor I'm guessing its a geared motor which will add more drag than a direct drive motor, hence the feeling of braking.
99% of geared hub motors have an internal one way clutch to allow pedaling with no drag. The motor rotor doesn't turn when the case is running faster.
however, wind drag at 25 kph is significant. I can't pedal that fast on the flat, sitting upright as I do. The lycra crowd that do ride that fast hunch over drop handlebars, looking at the ground all the time.
 

harryS

Well-Known Member
25Km/hour is 15.5 mph. That's not that fast, but it is quick for a folding bike. We have three 20" bikes, all home kits running on a 350W motors and 36V. These will run about 18-20 mph on a 36V, and up to 24mph on a 48V,

I see no speed sensor in your kit. Better hub motors have built-in sensors in the motor. Also see no single wires coming out of your controller used as speed limiters (you disconnect/connect them for speed limit control.)

What's the model number on the controller? How many amps? It looks like a KT controller. In fact, your display is a KT-display with a digital interface. It does have a speedometer on it too. If that is working, then the motor has a built speed sensor.


It probably means you could buy a KT LCD3 display which will be compatible, and is not locked for speed. They're not expensive. Again, you should do well over 20 mph with 48V, totally illegal in the UK, no?
 

steve marino

Active Member
The speed sensor is probably in the hub motor. You "may" be able to disconnect one of the wires on the controller and get around the speed limiter. Try disconnecting them one at a time and see what happens. If not, the ad does state that 25 is all it's gonna do, possibly due to your country's restrictions.

I use a free smart phone app called Digihud. It measures actual MPH or KM/H, fastest speed, average speed, distance, all that. Very handy. There's several other free apps that do this. I generally open the app, put the phone in my bag, forget about it until I get home, then ck it to see what things look like.
 
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harryS

Well-Known Member
Does the speedometer work on the 900S display? What does it read.

In order to give speed, the display needs to know the wheel diameter, so there will be a setup procedure to put that in. In addition, most KT displays set the maximum speed in the display via setup. I am thinking this unit is setup by copying the parameters from a different master display. KT displays have that functionality.

If you buy a different controller, and use this display, you're stuck with the same performance. Look first for a display upgrade, followed by controller. Or do both at same time.