Hobby Wheel Gadget Factory is proud to present the “Charge Doctor”, specifically designed to monitor the unicycles’ batteries.
It’s in fact an off-the-shelf USB charge monitor I have hacked and reprogrammed for our use.
BEWARE : Max current is 3 A. Plugging a 4A fast charger would toast the Charge Doctor !
- Voltage 40.0V – 80.0V
- Current 0.00 – 3.00A
- mAh-meter 0-19999 mAh
- Energy meter 0-999.9 Wh
- Connector 3-pin GX16 compatible with Airwheel & clones, TG, iezWay, Gotway, Firewheel… (not on Ninebot One with a different charge plug)
- Comm serial ascii output for logging, 9600 bauds, TTL levels
- Plug & play
First line: voltage and current.
Second line: total charge in mAh or Wh, click pushbutton (PB) to alternate between mAh and Wh.
Hold PB for 2 s to reset the total charge.
Hold PB for 6 s to enter calibration mode (see below).
Charge Doctor sends out data every 10s in ascii line format with ‘,’ separator, at 9600 bauds, TTL level
Line format: Seconds, Voltage (x10mV) , Current (x10mA) , Wh (x100mWh)
example 110,582,194,31 <=> 110s, 58,2V, 1.94A, 3.1Wh
Data are sent to a PC, MAC or Linux using TTL serial-USB converter dongle (cost < 2 $) and a terminal emulator for disk storage or graphic display. See this article for a setup example. Data can also be formatted using this Excel model. Look up “CP2102 USB converter” or “CH340G USB converter” on eBay (avoid PL2303HX chip based dongles which work fine but rather pricky when installing driver).
N.B. Charge Doctor does not store data. A PC must be connected during the charge to log data in real time.
Voltage is factory (ie by me) calibrated at +-20mV and current at +-2mA.
Recalibrate when necessary only if you have an accurate multimeter.
Press & hold the pushbutton (PB) for more than 6 s when the second counter is at the corresponding number :
1: decrease voltage gain (about 0,02V per PB click, so you must click 5x to see the number change)
2: increase voltage gain
3: decrease current gain (about 2mA per click)
4: increase current gain
5: reset current offset = 0 (no load)
The variable to be calibrated flashes and the change direction is indicated by the display’s up or down arrows.
The calibration mode ends after 10s of no PB click.
Charge Doctor display, charging a 260Wh empty battery.
1) beginning: V=60.2V, I=2.11A, Charge=29.1Wh
2) near end: V=67.1V, I=0.4A, Charge=230.8Wh
3) end of charge: V=67.1V, I=0.0A, Charge=243.4Wh
Notice that it’s a generic wheel (TG) battery with Chinese cells, so total charge is only only 243.4Wh, the nameplate “260 Wh capacity” cannot be reached. On the Firewheel 260Wh, with Panasonic cells, I can charge up to 285 Wh.
Serial link : blue=0V, orange=Transmit (connect to dongle’s RxD)