Key-Disp KD51C-D User manual

1
Product model
E-bike Intelligent LCD display
Model: KD51C-D
Specifications
●24V/36V/48V Power Supply
●Rated working current :10mA
●The maximum working current: 30mA
●Off-state leakage current: <1μA
●Operating temperature: -20℃~ 60℃
●Storage temperature: -30℃~ 70℃
Appearance and Size
Product appearance and dimension drawing (unit: mm)

2
Remote appearance and dimension drawing (unit: mm)
Function Summary
KD51C-D has many functions to meet your riding needs. The indicating contents are
as follows:
●Battery and battery percentage indication
●Motor Power indication
●assist-level indication
●Speed indication (incl. running speed, Max. speed and Ave. speed)
●Odometer and trip distance
●The push-assist function
●Trip time indication
●Backlight On/Off
●Error code indication
●Pedaling frequency indication(optional)
●USB connection indicator (optional)
●The remaining range indication(optional)
●Various Parameters Settings (e.g., wheel size, speed-limited, battery level bar,
assist level, controller limited current, password enable, etc.)
●Recover Default Settings

3
General Operation
◆Switching the E-bike System On/Off
Briefly press the power button to switch on the E-bike system, and provides the power
supply for the controller .To hold the power button for 2s, the E-bike system will be
switched off .The E-bike system no longer use the battery power.
When E-bike system is switched off, the leakage current is less than 1 μA.
■When E-bike is parked for more than 10 minutes, the E-bike system will be switched off
automatically.
◆Display Interface
After switching on the E-bike system, the display will show Current Speed and Trip
Distance by default. Press the “i”button will show more riding data as below:
Trip Distance (Km) →Total Distance (Km) →Max. Speed (Km/h) →Ave. Speed
(Km/h) →Ride Time (Min.) .
Display interface
◆Switching Push-assist Mode On/Off
To activate the push-assist function, keep holding “-”button. After 2s, The E-bike is
activated to go at a uniform speed of 6 Km/h while the screen shows “ ” . The
push-assist function is switched off as soon as you release the “-”button. The E-bike
system stops power output immediately.

4
Push-assist Mode
■Push-assist function may only be used while pushing the E-bike. Be aware of danger of
injury when E-bike wheels do not have ground contact.
◆Switching the Lighting On/Off
To switch on bike headlight, hold “ ” button for 2s. The display backlight brightness
is automatically reduced. In the same way, hold the “ ” button for 2s, the bike headlight
can be switched off while display backlight recover its brightness.
Switching the Lighting On/Off Interface
◆Power Assist Level Selection
Press "+" or "-" button to change the E-bike system assist level and change the motor
output power, The default assist level ranges from level “0”to level “5”, The output
power is zero on Level“0”. Level“1”is the minimum power. Level“5”is the maximum
power. When you reach “5”, press the "+" button again, the interface still shows “5”,
and blinks at“5”to indicate the power highest. After the power downshift reaches “0”,
press the "-" button again, the interface still shows “0”and blinks at “0”to indicate the
power minimum. The default value is level “1”.

5
Assist Level Change Interface
◆Battery Indicator
The five battery bars represent the capacity of the battery. The five battery bars are
bright when the battery is in high 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.
Battery Indicator
◆Motor Power Indicator
The power of the motor can be read via interface below by digits.
Motor Power Indication Interface
电

6
◆USB connection indication (optional)
When a USB external device is inserted into display, the USB connection indication
will be shown as follows:
USB Connection Indication Interface
◆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.
Here is the detail message of the error code in Attached list 1.
Error Code Indication
■Make the display repaired when an error code appears. You are not able to ride the electric
bike normally.
General Settings
Press the power button to switch on the display
To access general settings menu, hold both the “+”button and the “-”button
simultaneously for 2s.

7
General settings interface
▉All the Settings are operated in the case of a parked bike
◆Trip Distance Clearance
‘Clear Trip’ represents trip distance clearance setting.
To clear trip distance, press “+” button or “-” button to select the Yes or No. Yes
represents clearing a single ride distance. No represents not clearing a single ride
distance.
To store a changed setting, press the “i” button and then access General Settings
interface.
Trip Distance Clearance Settings Interface
◆Unit km/mile Conversion
‘Set Unit’ represents unit settings.
To convert unit, press the “+” button or the “-” button to choose the desired setting
item, and then press the “i” button to confirm.
To store a changed setting, press the “i” button and then exit general settings.
The default value is “Metric (km)”.

8
Mile and Kilometer Conversion Settings Interface
◆Wheel Diameter Settings
‘Wheel Diameter’ represents wheel diameter settings. To change basic settings,
press the “+” or the “-” button to increase or decrease until the desired value is displayed.
The default value is 26 inch. To store a changed setting, press the “i” button to confirm and
"OK" on display prompts for operation completed. Then access the General Settings
interface.
Wheel Diameter Settings Interface

9
◆Speed-limit Settings
The default value is 25Km/h.
‘Speed Limit’ represents the limited speed settings. When the current speed is faster
than speed limit, the E-bike system will switch off automatically. Speed limit range is
12Km/h to 40Km/h.
To change basic settings, press the “+” or the “-” button to increase or decrease until
the desired value is displayed. Press the “i” button to confirm and "OK" on display prompts
for operation completed.
To store a changed setting and exit General Parameter Settings, hold the “i” button
for 2s
Speed Limit Settings Interface
◆Battery Power Bar Settings
‘Set Voltage’ represents voltage settings. Each bar represents a voltage value. 5
bars voltage values must be entered one by one. For example, VOL 1 is first bar voltage
value. The default value is 31.5V.
To set battery power bar, press the “+” or the “-” button to increase or decrease the
number. To store a changed setting, press the “i” button and access the second bar,
You can set voltage values for other bars in the same way. After 5 bars voltage values
are entered, hold the “i” button to confirm and then return to previous menu.

10
Battery Power Bar Settings Interface
◆Power Assist Level Settings
1. Assist-Level Mode Options
‘Set Power’ represents power assist level settings. There are 8 assist-level modes for
your choice：0-3, 1-3, 0-5, 1-5, 0-7, 1-7, 0-9, 1-9. The default value is 0-5.
To change the mode of assist-level, press the “+” or the “-” button to choose the
desired mode and press the “i” button to confirm, then access PAS ratio settings
automatically.
PAS Mode Option Interface

11
2. PAS Ratio Settings
To change the value of PAS ratio, press the "+" button or "-" button to choose the
desired value, and then press the "i" button to confirm
For example, the ratio range is “45-55 percent” for level “1”, ratio value can be
changed and the default value is 50 percent.
To store a modified setting, press the “i” button and move to next PAS level ratio
settings.
After all PAS ratios are input, hold the “i” button for 2s to confirm and then return to
previous menu.
For PAS ratio default values, please refer to Attached list 2.
PAS Ratio Settings Interface
◆Controller Over-current Cut Settings
‘Set Current’ represents controller over-current cut settings. The current value can be
changed from 7.0A to 25.0A.
To change basic settings, press the “+” or the “-” button to increase or decrease the
value of the current.
To store a changed setting, hold the “i” button and then return to previous menu.

12
Current Settings Interface
◆Power Assist Sensor Settings
‘Assistant num’ represents PAS sensitivity settings. The sensitivity value is “5” to
“24”.
To store a changed setting, press the “i” button and then access the general settings.
To change the sensitivity of PAS sensor, press “+” or “-” button to select sensitivity
value.

13
PAS Sensitivity Settings
◆Speed Sensor Settings (optional)
‘Speed Sensor’ represents speed sensor settings. The default value is 1
To change speed sensor settings, press the “+” or the “-” button to select the quantity
of magnet head (the range is from 1 to 15).
To store a changed setting, hold the “i” button and then return to previous menu.
Speed Sensor Selection
◆Backlight Contrast Settings
‘Set Backlight’ represents backlight contrast settings. Level “1” is the low
brightness; Level “5” is high brightness. The default level is “1”.
To modify the backlight brightness, press the “+” button or the “-” button to choose the
desired setting brightness level.
To store a changed setting, press the “i” button and then access the General settings
interface.

14
Backlight Brightness Settings Interface
◆Power-on Password Settings
Password Settings on the screen means power-on password settings. The default
password is 1212.
To access the power-on password settings, press the“+”or the“-”button to modify
the value and then press the “i”button to confirm digit one by one until the correct 4-digit
password is completed, and then press the “i”button to access power-on password
enable settings interface, otherwise stay still in the password input state.
Enter Password Interface
◆Power-on Password Disable/Enable
To change power-on password enable/disable settings, press the “+”or the “-”
button to choose. Disable means not require a power-on password. Enable means a
power-on password is required.
If select Enable，press the “i”button and then access power-on password modify
interface, otherwise exit the power-on password settings interface.
The default value is Enable Password.

15
Set Password Interface
◆Power-on Password Change
When the display shows Password Set，Enter Password 0000, to set new power-on
password, press the “+”or the “-”button to modify the value and then press the “i”
button to confirm digit one by one until the new 4-digit password is completed.
To store the new power-on password, hold the “i”button for 2s and then exit
settings.
When you switch on the E-bike system next time, the display will show P1, 0000 and
input the new password to power on.
Change Password Interface
◆Exit Settings
In the settings state, press the “i” button (short than 2s) is to confirm the input. Hold
the “i” button (for more than 2s) is to store the settings, and then exit the current settings.
Hold the “-” button is to cancel the operation but not storing settings data, and then return
to previous menu.
■If there is no operations in one minute, the display will exit the settings state.

16
Quality Assurance and Warranty Scope
ⅠWarranty
（1）The warranty will be valid only for products used in normal usage 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 our warranty scope.
1、The display is demolished.
2、The damage of the display is caused by wrong installation or operation.
3、Shell of the display is broken when the display is out of the factory.
4、Wire of the display is broken.
5、The fault or damage of the display is caused by the force majeure (e.g., fire,
earthquake, etc.).
6、Beyond Warranty period.
Connection Layout
Connector wire sequence
Connector to controller Display end connection wire end to display end
Wire sequence table
Wire
Color
Function
1
Red（VCC）
﹢
2
Blue（K）
Lock
3
Black（GND）
﹣
4
Green（RX）
RX
5
Yellow（TX）
TX
■Some products have wire connection with water-proof connectors, users
can not see the color of wires in the harness.

17
Warnings:
1. Use the display with caution. Don’t attempt to disconnect or link the connector
when battery is on power.
2. Try to avoid hitting the display.
3. Don’t modify system parameters to avoid parameter disorder.
4. Make the display repaired when an error code appears.
▉THIS MANUAL INSTRUCTION IS A GENERAL-PURPOSE VERSION.SOME
OF THE VERSIONS FOR THE DISPLAY SOFTWARE WILL BE DIFFERENT FROM
SPECIFICATION TO SPECIFICATION. PLEASE ALWAYS REFER TO AN ACTUAL
VERSION
Attached list 1：Error code definition
Error code
Definition
21
Current Abnormality
22
Throttle Abnormality
23
Motor Phase Abnormality
24
Motor Hall Signal Abnormality
25
Brake Abnormality
30
Communication Abnormality
Attached list 2：PAS ratio default value table
Level
PAS
level mode
1
2
3
4
5
6
7
8
9
0-3/1-3
50%
74%
92%
—
—
—
—
—
—
0-5/ 1-5
50%
61%
73%
85%
96%
—
—
—
—
0-7/ 1-7
40%
50%
60%
70%
80%
90%
96%
—
—
0-9/ 1-9
25%
34%
43%
52%
61%
70%
79%
88%
96%