Charge Doctor V2, firmware V 2.03

Firmware V2.03 adds importants features to Charge Doctor’s V2.02. Please refer to this user manual for all CD shipped after June 2016, it replaces the now obsolete initial manual.

The CD is now available for a large range of electric wheels, from unicycles to hoverboards, bikes, scooters… It also exist in « mixte » versions for use on different models by the same CD (eg. Ninebot & Gotway). Here is a list of (non exhaustive) CD-compatible electric wheels :

  • Airwheels & clones, King Song, Gotway, Solowheel, Firewheel, Dolphin, Pinwheel…
  • Gotway 84V (GX16 4 pin connector)
  • IPS (GX16 4 pin connector)
  • Ninebot One (Lemo connector) an Minipro (GX12-4 pin connector)
  • InMotion V3 & V5 (Lenovo square socket) and V8 (GX12-3 pin connector)
  • Hoverboards
  • Scooter with XLR-3 pin connector or GX16-3 pin connector (GTX, Dualtron, Speedway,…)


Charge Doctor V2 features

  • Voltage: 20.0V – 100.0 V
  • Current : 0.00 – 10.00 A
  • Charge : 0.000-1000 Ah with automatic decimation
  • Energy : 0.0-10000 Wh with automatic decimation
  • End-of-charge by current threashold (0.1-8.0 A) or voltage threshold (30.0-85.0V)
  • Datalogging serial output 9600 bauds TTL
  • Dimensions : 85x50x20 mm
  • Weight : 65 g


At startup, displays « C-Dr » (blue) and firmware version « 2.03 » (red).


Top display shows alternatively voltage (« 61.9U ») and current in amps (« 1.99A »).

Image Image

Bottom display has 3 display screens:

Short click => screen change
1. Wh
2. Ah : « Ah » alternates with value to differentiate from Wh mode
3. Auto-shutdown threshold ( flashing display)
Long click
1. & 2. reset Ah and Wh counters
3. Enable/disable auto-shutdown (« —A » = disabled).
N.B. auto-shutdown threshold can
only be changed in « adjustment » mode
Image Image Image
screen 1: 148.2 Wh screen 2: 2.377 Ah screen 3: auto-cut threshold
short click =>change to screen 2
long click => Wh, Ah = 0
short click =>change to screen 3
long click => Wh, Ah = 0
short click =>change to screen 1
(automatically back to screen 1 if no click for more than 6s)

Screen 3 has 3 modes, press long click to change mode :

Image Image Image
screen 3 / mode 1 screen 3 / mode 2 screen 3 / mode 3
auto-cut when current is below threshold (1.20 A)

auto-cut disabled (use this mode to charge to 100%)

charge has been auto-cut (« off »). To resume charge, press long click or restart the CD by disconnect/connect charger

Easter egg: press 3 short clicks (interval < 0.3 between clicks) to turn off LED display
In display-off mode, the CD continues to work normally. Another click restores display


Enter adjustment mode by holding the button when powering on.
1) mode auto-shutdown, threshold adjustment : button hold < 5s
2) mode voltage & current calibration : button hold > 5s

1) Adjustement of auto-shutdown threshold

Top led displays current parameter. With no button click, the screen is cycled through 3 avaibles parameters every 2s. Any click holds up the actual parameter 6s for adjustment before the cycling restarts. Adjustment mode is terminated and the CD gets back to normal mode if no click for more than 10s.

Image 3 available parameters:

  • Auto : auto-cut
  • Pr1 : parameter 1, display off at auto-cut
  • Pr2 : parameter 2, auto-cut mode by current or voltage

« Auto » : auto-shutdown mode. Bottom led displays the shutdown threshold. When the threshold is reached, current is cut by the CD and the charge session is ended (I=0.00A). The threshold is incremented by 0.1A steps (auto-cut by current mode) or 0.1V steps (auto-cut by voltage mode). Hold the button for fast then ultra-fast increment. Voltage and current threshold are stored in separate non-volatile memories.
Important: disabling auto-cut can not be done in « parameter mode » only in normal mode (see above).

« Pr1 » : parameter 1. Value = 1 => deep standby mode with Led display off at auto-cut. To power on, click button or disconnect/reconnect the CD.

« Pr2 » : parameter 2. Available values, « dn A », « up V », « dn V »

Image Image Image
dn A : down A, auo-cut when charge current is below threshold. Default mode at first use.

UP V : auto-cut when charge voltage is above threshold. This mode generally allows more accurate auto-cut, to be used on big batteries (>560Wh) when auto-cut by current doesn’t have enough resolution.

dn V : down V, auto-cut when voltage drops below threshold. To be used only for discharge tests.




2) Calibration

Voltage and current are calibrated at +-10mV and +-1mA respectively before shipping. Avoid recalibration unless you have accurate instrumentation.

Top led displays actual parameter. With no button click, parameters changes every 2s in a round robin schedule for all available parameters. Any click keeps the actual parameter 6s before the round-robin restarts. To quit this calibration mode and revert back to normal mode, power-off then on Charge Doctor.

« down U » : decrease voltage gain
(about 10mV per click)
« UP U » : increase voltage gain
« down A » : decrease current gain
(about 1mA per click))
« UP A » : increase current gain
« 00 A » : change current offset to calibrate 0.00A
ATTENTION : connect no charge (zero current) and hold button 2s to calibrate (short click is ignored to filter out manipulation error)

Data logging

Charge-Doctor transmits data every 10s by serial 9600 bds protocol, TTL level, 8 bit data, 1 bit stop, no parity. Data are in ASCII format with separator = coma. The format is identical to the first version Charge Doctor, see the blog’s article on Graphic Display for steps to download and process data in realtime.
N.B. Charge Doctor does not store data. For data logging, a PC must be connected during all the charge record.

Connection to dongle : the Charge Doctor’s output Tx must be connected to the serial-USB converter dongle’s input Rx :


IMPORTANT : at power-up, Charge Doctor sends a 2 line header containing various information such as the firmware version :

Charge Doctor V2.00-10A by HMC 01/2015
Time(s) Voltage(x0.1V) Current(x10mA) Charge(x0.1Wh)

These two lines will be recorded in file « log.txt » but they are not parsable by the grapher KST so the realtime display will stop : KST is quite pricky as to the data format and any error will stop the graph updates. Data and graph should change in realtime in KST when new data is logged into « log.txt » by datalogger.exe so if KST’s display freezes, then « log.txt » contains errors. To remove errors, quit KST and edit « log.txt » using a text editor.

The ininterpretable header lines can be removed from « log.txt » by two methods :

  • restart datalogger.exe 2 secondes AFTER restarting Charge Doctor so the header gets lost and not logged
  • Click « Stop logging », UNcheck option « Append to file » then click « Start logging » in datalogger.exe => old file « log.txt » is deleted and replaced by a new blank file for logging, hence, without the uninterpretable header.

Pictures of Charge Doctor V2, versions with GX16 connector (most electric monocyles, bike, hoverboard, bikeboard) and Lemo connector (Ninebot monocycle).
(click picture for high resolution image)



4 réflexions sur « Charge Doctor V2, firmware V 2.03 »

    1. hobby16 Auteur de l’article

      the Z10 uses a special non-standard connector.
      I haven’t figured out what it is or where to procure it, so no Charge Doctor for Ninebot Z10, yet.

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