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 area distribution................................................................................................................................................. 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 information............................................................................................................................................. 8
◆Wheel diameter information.............................................................................................................................................8
◆Speed limit information..................................................................................................................................................... 8
Personalized parameters settings&information....................................................................................................................9
◆Battery power bar settings............................................................................................................................................. 10
◆Assist level settings......................................................................................................................................................... 10
Assist level mode options settings............................................................................................................................... 10
Assist level ratio information......................................................................................................................................... 11
◆Controller over-current cut information(optional)...................................................................................................... 11
◆Power assist sensor information (optional)................................................................................................................ 12
PAS direction information.............................................................................................................................................. 12
PAS sensitivity information............................................................................................................................................12
PAS magnet quantity information.................................................................................................................................13

◆Speed sensor information(optional)............................................................................................................................ 13
◆Throttle function information(optional)........................................................................................................................ 14
Throttle push assist enable/disable information........................................................................................................ 14
Throttle level enable/disable information.................................................................................................................... 14
◆System settings&information（optional）................................................................................................................. 15
Battery power delay time settings................................................................................................................................ 15
Push assist button enable/disable information.......................................................................................................... 16
Slow start up information............................................................................................................................................... 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 3：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 Information and 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 ( , , ) .

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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.
If “On/Off” button or “-” button is sticky, an error code will be shown on the screen. Please refer to
Attached List 1 as for “sticky button” error code definition details.
If an improper operation by user occurs (eg. an excess pressing on “On/Off” button or pressing
“On/Off” button and “-” button simultaneously ), the user can switch off the display and restart.
■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)→ODO (Km)→ Max. Speed
(Km/h)→ Avg. Speed (Km/h) , it cycles back to ODO km again.

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Display indication cycle interface
◆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.

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Switching Lighting on/off
◆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”
◆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

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Flash (low voltage)
Battery Indicator
◆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 3.

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Trip Distance Clearance Settings Interface
◆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.

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Mile and Kilometer toggling Settings Interface
General Parameter Information
To access general parameter information 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 Information.
◆Wheel Diameter Information
Ld represents wheel diameter information. Press ON/OFF button and access speed-limit
information interface.
Wheel Diameter Information Interface
◆Speed limit Information
LS represents the speed limit information. Hold the ON/OFF button for 2s to exit General
Parameter Information.
Speed Limit Information Interface

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Personalized Parameter Settings&Information
Personalized Parameter Settings&Information can meet a variety of riders’ personalized
requirements. 8 options are Battery Power Bar Settings, Power assist level Settings, Over-current Cut
Information, Power Assist Sensor Information, Speed Sensor Information, Throttle Function Information,
System Settings&Information and Power-on Password Settings. Please refer to Attached list 2 for the
definition of the symbols. Some versions of displays, conditional upon protocols will not have setting
items from “3” to “7”
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&Information interface.
Press UP or DOWN button to choose the personalized parameter for checking and settings, then
press ON/OFF button to enter the corresponding interface.
Setting Item Cycle Interface

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◆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 Setting Interface
Assist Level Ratio Information
Short press ” ON/OFF” button to check about ratio value of each assist level.

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Hold the “ON/OFF” button for 2s to return to previous menu.
Assist Level Ratio Interface
◆Controller Over-Current Cut Information
CUR represents controller over-current cut information. .
Press the ON/OFF button and then return to previous menu.
Current Information Interface
◆Power Assist Sensor Information
PAS represents power assist sensor information.
Power Assist Sensor Direction Information
“run-F” means forward direction while “run-b” means backward direction.
Press the ON/OFF button and then access PAS sensitivity information.
PAS Direction Information
PAS Sensitivity Information

12
SCN represents PAS sensitivity settings.
Press the ON/OFF button and then access magnet disk information.
PAS sensitivity Information
PAS Magnet Quantity Information
Nrepresents the number of magnets on PAS disk.
Hold the ON/OFF button for 2s to return to previous menu.
PAS Disk Magnet Quantity information
◆Speed Sensor Information
SPS represents speed sensor information.
Hold the ON/OFF button for 2s to return to previous menu.
Speed Sensor information
◆Throttle Function Information
Throttle Push-assistance Enable/Disable Information
HL represents throttle push-assistance function.

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HL-N means throttle push-assistance function is disabled.
HL-y means throttle push-assistance function is enabled.
.
Throttle Push-assistance Enable/Disable Interface
Throttle Level Enable/Disable Information
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.
ymeans the maximum speed can only be the highest speed powered by current power assist level
when you twist the throttle.
nmeans 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.
Hold the ON/OFF button for 2s to return to previous menu.
Throttle Level Enable or Disable Interface
◆System Settings and Information
Delay time settings for battery power
DLY represents battery power delay time settings. The default value is 3s.

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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 settings Interface
Push-assistance Enable/Disable information
PUS represents push-assistance enable/disable settings. “Y” means push-assistance is enabled, “N”
means push-assistance is disabled.
Press the ON/OFF button to access slow start up settings.
Push-assistance information Interface
Slow Start up Information
SSP represents slow start up.
Press the ON/OFF button and moves to Delay time information for battery power.
Hold the ON/OFF button for 2s to return to previous menu, .
Slow Start-up Information Interface
◆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

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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.
Password Input Interface
Power-on Password Enable/Disable
Press UP or DOWN button to choose Y or N and press ON/OFF button 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 “ON/OFF” 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
Power-on Password Change
When the display shows P3, 0000, press UP/DOWN to change the number and then press ON/OFF
button to confirm digits one by one until a new 4-digit password is completed.
To store the new power-on password, hold ON/OFF button for 2 s and then exit settings.
When you switch on the E-bike system next time, the display will show P1,0000, please input
the new password to power on.

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Power-on Password Change Interface
◆Exit settings
In Personalized Parameter Settings&Information Interface,
Press the ON/OFF button is to confirm the input.
Hold the ON/OFF button is to store the settings and exit the current setting.
Hold the DOWN button is to cancel the operations but not to store setting data and return to
previous menu.
■If there is no operations in two minutes, the display will exit the settings interface.
Recover default settings
dEF represents recovering default settings. The default value is N.
To access recover default settings, hold both UP and ON/OFF button for 2s and then access
selection interface. Press the UP/DOWN button to choose “Y” or “N”. “N” means not recovering default
settings. Y means recovering default settings.
When it is “Y”, hold the ON/OFF button for 2s to recover default settings, the display shows DEF-00
at the same time and returns to display start-up page .
Recover Default Settings Interface

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Quality assurance and warranty scope
ⅠWarranty
1) The warranty will be valid only for products used in normal usage and conditions.
2) The warranty is valid for 24 months after the shipment or delivery to the customer.
ⅡOthers
The following cases do not belong to warranty scope:
1) The display is demolished.
2) The damage of the display is caused by wrong installation or operation.
3) The shell of the display is broken after the display is out of the factory.
4) The cable of the display is broken.
5) Beyond warranty period.
6) The fault or damage of the display is caused by the force majeure (e.g., fire, earthquake, etc.)
Connection layout
Connector wire sequence
Connector to controller display end connection wire end to display end
Wire sequence table
Wire sequence
Color
Function
1
Red(VCC)
+
2
Blue(K)
Lock
3
Black(GND)
-
4
Green(RX)
RX
5
Yellow(TX)
TX