Key-Disp KD21C User manual

Contents
Product name and model......................................................................................................................................................... 1
Specifications............................................................................................................................................................................. 1
Appearance and dimension..................................................................................................................................................... 1
Function and button definition................................................................................................................................................. 2
◆Function summary............................................................................................................................................................. 2
◆Function layout................................................................................................................................................................... 2
◆Button definition................................................................................................................................................................. 2
Installation................................................................................................................................................................................... 3
General operations.................................................................................................................................................................... 3
◆Switch E-bike system ON/OFF........................................................................................................................................3
◆Display interface.................................................................................................................................................................3
◆Switch push-assistance mode ON/OFF......................................................................................................................... 4
◆Switch lighting ON/OFF.................................................................................................................................................... 4
◆Assist level selection......................................................................................................................................................... 5
◆Battery indicator................................................................................................................................................................. 5
◆Error code indication......................................................................................................................................................... 6
General Settings........................................................................................................................................................................ 6
◆Trip distance clearance.................................................................................................................................................... 6
◆Backlight brightness.......................................................................................................................................................... 7
◆Toggle the unit KM/miles..................................................................................................................................................7
General parameters settings................................................................................................................................................... 8
◆Wheel diameter..................................................................................................................................................................8
◆Speed limit.......................................................................................................................................................................... 8
Personalized parameters settings.......................................................................................................................................... 9
◆Battery power bar settings............................................................................................................................................. 10
◆Assist level settings......................................................................................................................................................... 10
Assist level mode options.............................................................................................................................................. 10
Assist level ratio settings............................................................................................................................................... 11
◆Controller over-current cut settings(optional)............................................................................................................ 11
◆Power assist sensor settings(optional)....................................................................................................................... 12
PAS direction settings.................................................................................................................................................... 12
PAS sensitivity settings.................................................................................................................................................. 12
PAS magnet quantity settings.......................................................................................................................................13

◆Speed sensor settings(optional).................................................................................................................................. 13
◆Throttle function settings(optional).............................................................................................................................. 14
Throttle push assist enable/disable settings.............................................................................................................. 14
Throttle level enable/disable settings.......................................................................................................................... 14
◆System settings（optional）........................................................................................................................................15
Battery power delay time settings................................................................................................................................ 15
Maximum speed limits....................................................................................................................................................15
Push assist button enable/disable............................................................................................................................... 16
Slow start up settings..................................................................................................................................................... 16
◆Power-on password settings..........................................................................................................................................17
Power-on password Enable/Disable............................................................................................................................17
Power-on password change..........................................................................................................................................18
◆Exit settings...................................................................................................................................................................... 18
Recover default settings.........................................................................................................................................................19
Quality assurance and warranty scope............................................................................................................................... 19
Wire connection layout........................................................................................................................................................... 20
Warnings................................................................................................................................................................................... 20
Attached list 1：Error code definitions.................................................................................................................................21
Attached list 2：Personalized settings symbols................................................................................................................ 21
Attached list 2：Assist level ratio defaults.......................................................................................................................... 21
Attached list 4：Other symbols.............................................................................................................................................21

1
Product name and model
E-bike Intelligent LCD Display
Model: KD21C.
Specifications
●24V/36V/48V Power Supply
●Rated working current: 10mA
●The maximum working current: 30mA
●Off-state leakage current: <1μA
●Working temperature:-20℃~ 60℃
●Storage temperature: -30℃~ 70℃
Appearance and Size
Product appearance and dimensional drawing (unit: mm)

2
Function Summary and Button Definition
◆Function Summary
KD21C has many functions to meet riders’ needs. The indication elements are as follows：
●Battery level
●Motor output power
●Assist level
●Speed indication (incl. current speed, Max. speed and Avg. speed)
●ODO and Trip
●Push-assistance function
●Trip time
●Backlight ON/OFF
●Error code indication
●Various Parameters Settings (e.g. wheel diameter, speed limit, battery power bar, assist level,
current limit, maximum speed, password enable, etc.)
●Recover Default Settings
◆Functional Area Distribution
◆Button Definition
There are three buttons ( , , ) on KD21C display. In this manual, we use words ON/OFF,
UP, DOWN to represent these 3 symbols ( , , ) .

3
Installation
KD21C can be mounted on the left side of handlebar close to its grip. Adjust the angle for a good
screen view. Cut off the power before connecting the corresponding connectors between display and
controller.
General Operation
◆Switching the E-bike System mode ON/OFF
To switch on the E-bike system and provide the power supply to the controller, hold the On/Off
button for 2s.
To switch off E-bike system, hold the On/Off button for 2s. The E-bike system no longer uses
the battery power.
When E-bike system is switched off, the leakage current is less than 1 μA.
■When the E-bike is parked for approx. 10 minutes, the E-bike system switches off
automatically.
◆Display Interface
After switching on the E-bike system, the display shows Current Speed and ODO(total distance)
by default.
Press the ON/OFF button to switch between indication functions below:
ODO (Km)→ Trip (Km) → Trip Time (Hour) → Motor Power (W)→ Max. Speed (Km/h)→ Avg.
Speed (Km/h) →ODO (Km). Finally, it cycles back to ODO km again.
Display indication cycle interface

4
◆Switching Push-assistance mode ON/OFF
To activate the push-assistance function, press and hold the DOWN button. After 2 seconds, E-bike
is activated to go at a uniform speed of 6 Km/h while the screen displays “P”.
The push-assistance function will be switched off as soon as you release the DOWN button.
Push-assistance mode
■Push-assistance function may only be used when pushing the E-bike. Be aware of danger of
injury when bike wheels do not have ground contact while using the push-assistance function.
◆Switching Lighting ON/OFF
To switch on E-bike front light or rear light, press the “UP” button for 2s. The display backlight
brightness is automatically reduced while the screen displays “ ”.
Likewise, press the “UP” button for 2s again, the bike front light and rear light can be switched off
and display backlight recover its brightness.
*If E-bike front light or rear light is independent of “UP” button, the “UP” button can only be used to
switch on/off the display backlight.
Switching Lighting on/off

5
◆Assist Level Selection
The assist level of the E-bike drive can be changed anytime, even during riding.
The assist level ranges from 0 to 5 (level 0 to level 5). The default assist level is “1” when the display
is started. The output power is zero on Level “0”. Level “1” is the minimum output power. Level “5” is the
maximum output power.
Press UP/DOWN button to switch between the E-bike system assist levels and change the motor
output power.
Assist Level “3”
◆Manual clearance functions
Amid all indication functions, Trip Distance, Max Speed and Avg. Speed can only be cleared manually.
If the above functions need to be cleared, hold ON/OFF button and the DOWN button for 2s, the above
functions can be cleared simultaneously.
◆Battery Indicator
The five battery power bars represent the capacity of the battery. The five battery bars are
bright when the battery is in full voltage. When the battery is in low voltage, battery frame will
flash at the frequency of 1HZ to give a notice that the battery needs to be recharged immediately
Flash (low voltage)
Battery Indicator

6
◆Error Code Indication
The components of the E-bike system are continuously and automatically monitored.
When an error is detected, the respective error code is indicated in text indication area.
Refer to detailed definition of the error codes in Attached list 1.
Error Code Indication
■Have the display inspected and repaired when an error code appears. Or else, you will not be
able to ride the bike normally. Please always refer to an authorized bicycle dealer.
General Settings
After the E-bike system is switched on, hold both the UP button and DOWN button simultaneously for
2s to access general settings menu.
■All the Settings are completed on a parked E-bike.
◆Trip Distance Clearance
TC represents trip distance clearance settings.
Press the UP/DOWN button to choose Y or N. The default value is N.
To store a changed setting, press the ON/OFF button and access backlight settings.
For symbols and their definitions, please refer to Attached list 4.
Trip Distance Clearance Settings Interface

7
◆Backlight settings
bL represents backlight settings. Level “1” is the lowest brightness. Level “2” is the medium
brightness. Level “3” is the highest brightness. The default value is “1”.
To change the backlight brightness, press the UP/DOWN button to increase or decrease until the
desired brightness is displayed.
To store a changed setting, press the ON/OFF button and access unit toggling settings.
Backlight Brightness Setting Interface
◆Unit km/mi toggling
Urepresents unit settings, “1” is mile, and “2” is kilometer. The default value is “2”.
To toggle the unit, press the UP/DOWN button until the desired unit is displayed.
To store a changed setting, press the ON/OFF button and access trip distance clearance settings
again or hold the ON/OFF button for 2s to exit General Settings.
Mile and Kilometer toggling Settings Interface

8
General Parameter Settings
To access general parameter settings interface, hold both the UP and the DOWN button
simultaneously for 2s to enter General Settings, then hold both the DOWN and ON/OFF button for 2s
again to enter General Parameter Settings.
◆Wheel Diameter Settings
Ld represents wheel diameter settings. Optional values are 16, 18, 20, 22, 24, 26, 700C and 28.
The default value is 20 inch.
Press the UP/DOWN button to increase or decrease wheel diameter until the desired value is
displayed.
To store a changed setting, press ON/OFF button and access speed-limit settings interface.
Wheel Diameter Settings Interface
◆Speed limit Settings
LS represents the speed limit settings. When the current speed is faster than speed limit, the E-bike
system will be switched off automatically. Speed limit ranges from 12Km/h to 40Km/h. The default value
is 25Km/h.
Press the UP/DOWN button to increase or decrease the speed limit values until the desired one is
displayed.
To store a changed setting, press ON/OFF button and access wheel diameter setting again or hold
the ON/OFF button for 2s to exit General Parameter Settings.
Speed Limit Settings Interface

9
Personalized Parameter Settings
Personalized Parameter Settings can meet a variety of riders’ personalized requirements. 8
settings are Battery Power Bar Settings, Power assist level Settings, Over-current Cut Settings, Power
Assist Sensor Settings, Speed Sensor Settings, Throttle Function Settings, System Settings and Power-
on Password Settings. Please refer to Attached list 2 for the definition of the symbols.
Hold UP and DOWN button simultaneously for 2 seconds to enter General Settings and Hold UP
and DOWN button simultaneously for another 2 seconds to enter Personalized Parameter Settings
interface.
Press UP or DOWN button to choose the personalized parameter setting item, then press ON/OFF
button to enter the corresponding setting interface.
Setting Item Cycle Interface

10
◆Battery Power Bar Settings
VOL represents voltage settings. Each bar represents a voltage value. Each of the 5 values is to be
entered one by one. For example, VOL 1 is the first bar voltage value, the default value is 31.5V. Press
UP or DOWN button to increase or decrease the bar value and press ON/OFF button to store a
changed setting and access the second bar. Likewise, you can set the values in the same manner for
other bars. After values for 5 bars are entered completely, press ON/OFF to confirm and return to the
previous menu.
Battery Bar Settings
◆Assist Level Settings
SCA represents assist level settings.
Assist Level mode options
There are 8 assist level modes:0-3, 1-3, 0-5, 1-5, 0-7, 1-7, 0-9, 1-9. The default mode is 0-5.
Press the UP/DOWN button to increase or decrease until the desired mode is displayed.
Press the ON/OFF button and access the assist level ratio settings automatically.
“1-5” flash
Assist Level Mode Interface

11
Assist Level Ratio Settings
The speed of each level can be adjusted to meet different riders’ needs by setting the ratios.
For example, the default ratio is 50% for level “1”; the ratio range is 45%-55% for Level ”1”.
To change the ratio of a certain assist level, press the UP/DOWN button to choose the desired
ratio value, and then press the "ON/OFF" button to confirm and then move to the next level ratio
setting.
After ratios of all levels were input, hold the “ON/OFF” button for 2s to confirm and return to
previous menu.
*Please refer to assist level ratio default values Attached list 3
Assist Level Ratio Interface
◆Controller Over-Current Cut Settings
CUR represents controller over-current cut settings. CUR value ranges from 7.0A to 22.0A. The
default value is 15A.
Press the UP/DOWN button to increase or decrease the value of the current.
Press the ON/OFF button and then return to previous menu.
Current Settings Interface

12
◆Power Assist Sensor Settings
PAS represents power assist sensor settings.
Power Assist Sensor Direction Settings
“run-F” means forward direction while “run-b” means backward direction. The default value is
“run-F”.
Press the UP/DOWN button to select For bto change the direction of Power Assist Sensor.
Press the ON/OFF button and then access PAS sensitivity settings.
PAS Direction Settings
PAS Sensitivity Settings
SCN represents PAS sensitivity settings. The sensitivity value ranges from “2” to “9”. “2” is the
strongest, “9” is the weakest. The default value is “2”.
Press the UP/DOWN button to choose sensitivity value to change the PAS sensitivity settings.
Press the ON/OFF button and then access magnet disk settings.
PAS sensitivity Settings

13
PAS Magnet Quantity Settings
Nrepresents the number of magnets on PAS disk. The default value is 12.
Press the UP/DOWN button to select the number of magnets on PAS disk.
Hold the ON/OFF button for 2s to confirm and return to previous menu.
PAS Disk Magnet Quantity settings
◆Speed Sensor Settings
SPS represents speed sensor settings. The default value is 1.
Press the UP/DOWN button to choose the number of spoke magnets on the bike wheel. The range is
from 1 to 9.
Hold the ON/OFF button for 2s to confirm and then return to previous menu.
Speed Sensor settings

14
◆Throttle Function Settings
Throttle Push-assistance Enable/Disable
HL represents throttle push-assistance function. HL-N means throttle push-assistance function is
disabled. HL-y means throttle push-assistance function is enabled. The default value is HL-N.
Press the UP/DOWN button to select Y or N to enable or disable throttle push-assistance function .
To enable throttle push-assistance, select Y and hold ON/OFF button for 2s to confirm and return to
previous menu.
To disable throttle push-assistance, select N and access Throttle Level Enable/Disable Setting
below
.
Throttle Push-assistance Enable/Disable Interface
Throttle Level Enable/Disable
HF-y means throttle speed is limited by current power assist level while HF-n means throttle speed
is not limited by current power assist level. The default value is n. Press UP/DOWN to set yor n.
If you choose y, the maximum speed can only be the highest speed powered by current power
assist level when you twist the throttle.
If you choose n, the maximum speed is not limited by current power assist level and you can
override whatever level you are in and reach rated maximum speed when you twist the throttle.
To store a changed setting, press ON/OFF button to confirm and return to throttle push-assistance
enable/disable setting interface or hold ON/OFF button for 2s to confirm and return to previous
menu.
Throttle Level Enable or Disable Interface

15
◆System Settings
Delay time settings for battery power
DLY represents battery power delay time settings. The default value is 3s.
Press the UP/DOWN button to choose delay time 3s, 6s, 12s to change the settings.
Press the ON/OFF button to confirm and access the max speed limit settings.
Battery power delay time Interface
Max speed limit settings
MAX SPD represents max speed limit settings. The default value is 40Km/h.
Press the UP/DOWN button to set the max speed from 25Km/h to 40 Km/h.
Press the ON/OFF button to confirm and then access Push-assist settings
Interface of Max Speed Limit Settings
■The maximum speed upper limit is set by the display manufacturer.

16
Push-assistance Enable/Disable
PUS represents push-assistance enable/disable settings. “Y” means push-assistance is enabled, “N”
means push-assistance is disabled. The default value is “Y”.
Press the UP/DOWN button to choose “Y” or “N” to change push-assistance settings.
Press the ON/OFF button to confirm and then access slow start up settings.
Push-assistance settings Interface
Slow Start up Settings
SSP represents slow start up. The range is “1-4”, “4” is the slowest. The default value is “1”.
To change slow start up settings, press the UP/DOWN button to choose the desired value.
Press the ON/OFF button and moves to Delay time settings for battery power.
Hold the ON/OFF button for 2s to return to previous menu, .
Slow Start-up Settings interface

17
◆Power-on Password Settings
PSd represents power-on password settings. Power-on password is a 4-digit code. The default
password is “1212”.
Press ON/OFF button to enter the interface where “P2, 0000” is shown on the screen. Please input
the current password or default password’1212’.
Press UP/DOWN button to increase or decrease the number and press ibutton to confirm digits one
by one until the correct 4-digit password is completed. Press ON/OFF button to access power-on
password Enable/Disable Settings.
Otherwise stay in password input state.
Password Input Interface
Power-on Password Enable/Disable
Press UP or DOWN button to choose Y or N and press ibutton to confirm. Y means power-on
password is enabled. N means power-on password is disabled. The default value is N.
If you choose Y, press the “i” button and then access power-on password change interface.
If you choose N, you will exit the power-on password settings interface and return to previous menu.
Power-on Password Disable Interface