Help on speed display.

[polis2022]

Hello everybody,
My electric bike is DME fractum 24 fatbike.
Bafang 500w 48v hub rear motor with KD21C display.
I have reset the default values of the display and now it does not show me the speed. Although I put the wheel size at 24 inches and setting pas at 12 magnets, the speed always remains at 0.
In the section of the display in "SPs" Speed sensor I can put the values from 1 to 63. What value do I put?
Can anyone help me thanks. Before, everything worked fine.
I enclose the manual of the display. Thanks a lot.

User MAnual KD21C

 

[Nealh]

Speed sensor setting should I think be 1 for one motor speed magnet if that doesn't work try 5 or 6.

 

[polis2022]

I tried the values up to 12, the speed starts scoring, even if it's busted, with the value 43 44 45 46 etc. Can anyone tell me how to calculate this value, thanks.

 

[Nealh]

Page 18 describes the recover default settings have you tried this again ?

 

[polis2022]

Yes, for what I have reset the values now the speed meter does not work. As soon as I understood the sensor is inside the engine.

 

[Nealh]

Yes the internal sensor is a hall and simply has 1 or 6 magnets on the side plate/cover that it will pick up on, the speed magnet setting for the speed reading needs to be set to either 1 or 6, but I do remember d8veh sometime ago mention that some Bafangs hubs may only use 5 magnets. These magnets are totally different from the PAS sensing magnets on the BB so don't be confused by counting those.

 

[Nealh]

Also is there a P1 type setting that needs a figure set for the motor internal gearing multiplied by the motor winding magnets, if so for a Bafang hub this value is usually around the 84 mark and should be input as so.

 

[polis2022]

Yes the internal sensor is a hall and simply has 1 or 6 magnets on the side plate/cover that it will pick up on, the speed magnet setting for the speed reading needs to be set to either 1 or 6, but I do remember d8veh sometime ago mention that some Bafangs hubs may only use 5 magnets. These magnets are totally different from the PAS sensing magnets on the BB so don't be confused by counting those.

But the pas sensor is used to measure the speed?
My engine is this; Motor bafang.

 

[sjpt]

But the pas sensor is used to measure the speed?

PAS sensor can't measure the speed as it doesn't know about gearing.
It could measure pedal cadence, but generally it is just used to detect 'are you pedalling, Yes/no?'.

 

[polis2022]

So what value should i try from 1 to 63? since up to 12 do not work. Is there any formula to calculate this number? Thank you.

 

[Nealh]

There must be a setting for motor speed magnets not PAS sensor magnets.
On my system the setting is also known as wheel speed pulse.

 

[polis2022]

There must be a setting for motor speed magnets not PAS sensor magnets.
On my system the setting is also known as wheel speed pulse.

ok, how do i find the value?

 

[Nealh]

On Page 12 the setting is speed sensor option the value is set to 1.
It is not the same as Magnet quantity settings which is how many PAS magnets that are in the magnet disc.

 

[polis2022]

Ok, thanks the same, but do not work.

 

[Nealh]

ok, how do i find the value?

The value is the number of speed magnets fitted in the motor, it will either be 1 or 6. I have already mentioned this.
All hub bikes have three different types of magnet counts.
1. PAS magnet discs, all these magnets do it sense the delay for the motor to react to pedalling, the more magnets the quicker the motor kicks in.
2. Motor speed magnets these are used to detect the wheel speed reading usually 1 magnet but some have 6.
3. Motor winding/coil magnets, these are placed around the circumference of the copper windings to produce the force field.

 

[Nealh]

Ok, thanks the same, but do not work.

Try 6 then, if that doesn't work try the four numbers between.
Other wise I don't know why it isn't working unless of course the hall sensor in the hub has failed.

 

[polis2022]

ok

 

[Nealh]

Sometimes the magnet inside the hubs outer cover /lid can become detached if that is so then one will see 0 mph reading.

 

[Nealh]

I tried the values up to 12, the speed starts scoring, even if it's busted, with the value 43 44 45 46 etc. Can anyone tell me how to calculate this value, thanks.

Is the speed reading set for km/h or mph ?

 

[polis2022]

Sometimes the magnet inside the hubs outer cover /lid can become detached if that is so then one will see 0 mph reading.

It's not my thing to take the engine apart. I'll give you an update. Pedaling backwards marks the speed. Pedaling forward gives me another busted value.
Now I attached the photo with the characteristics of the engine. In fact they are 6 magnets.