Charge Doctor V2 – 10A

Charge Doctor V2 is an upgrade of the previous battery charge controller. It retains the original features of the product like a selectable charge display in Wh or Ah, user-recalibration and storage of calibration factors in eeprom, one-button user interface, datalogging by a transmit serial output. Enhancements have been added :

  • maximum current up to 10A
  • wider voltage range
  • bigger display digits
  • end-of-charge auto shutdown with adjustable current threshold

With its wider range of voltages and currents, V2 is suitable for charge monitoring of most light electric vehicules, especially electric monowheels, but also bikes, scooters, hoverboards, gyropods, e-bikeboards…


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 adjustable current threashold : 0.1-8.0 A
  • Datalogging serial output 9600 bauds TTL
  • In/out with 3-pin GX16 aviation connector (Airwheel & clones, TG, iezWay, Gotway, Firewheel, most e-bikeboard…) or Lemo connector for Ninebot
  • Dimensions : 85x50x20 mm
  • Weight : 65 g


At startup, displays “C-Dr” (top) and firmware version “2.00” (bottom).


Top display shows alternatively voltage (“65.7U”) and current in amps (“1.99A”).

Image Image

Bottom display has 3 display modes :

Short click => mode change
1. Wh
2. Ah : “Ah” alternates with value to differentiate from Wh mode
Auto ; flashing display of auto-shutdown current threshold
( auto-shutdown disabled => current = 0.00A)
Long click
1. & 2. reset Ah and Wh counters
3. Enable/disable auto-shutdown (“0.00A” = disabled).
N.B. auto-shutdown threshold can
only be changed in “adjustment” mode

Important : after auto-shutdown, the internal switch is in OFF state and no current can pass. To enable charging again, switch ON the internal switch using either methods :

  • long click when in auto-shutdown mode (see above)
  • disconnect/reconnect Charge Doctor (internal switch is always ON at startup)


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

1) Adjustement of auto-shutdown current threshold

Top led displays actual parameter. With no button click, parameters changes every 2s in a round-robin schedule for all available parameters. Any click hold up the actual parameter 6s before the round-robin cycle restarts.
“Auto” : auto-shutdown mode. Bottom led displays the shutdown threshold ( “1.00A”). When charge current drops below this threshold, charging is stopped by Charge Doctor. Change by 0.1A steps by clicking the button or by holding the button
Important : disabling auto-shutdown (display = “0.00A”) can only be done in normal mode (see above), not in adjustment mode
“Pr1” : parameter 1. Value = 1 => deep standby mode with Led display off at auto-shutdown. To power on, click button or disconnect/reconnect Charge Doctor.
“PR2”, … “PRn” : future extension

If no click for more than 6s, this adjustement mode is terminated and Charge Doctor reverts back to normal mode.

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)



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