Battery Doctor

The large screen is easy to read.

If you’re like me, you can never have too many gadgets although granted I suspect that, also like me, some of your purchases see the light of day more often than others. I’ve grown quite attached to this new little widget from CML Distribution which has seen a lot of use on my workbench over the last few months. Primarily designed for Li-Po/Li-Fe batteries, it has a number of functions :-

• Cell Balancing before, after or during pack charging.
• Pack and individual cell voltage measurement.
• Pack discharging.
• Receiver battery voltmeter.

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Battery Doctor can handle 2-6 cell Li-Po/Li-Fe batteries, the unit houses a row of JST-XH plug sockets into which packs are connected for measurement, balancing or discharge. While JST-XH is a popular balance connector type, converter leads will need to be sourced if packs fitted with other connector types are to be treated.
A large, clear LCD screen shows what’s going on and hooking up a battery will prompt the display to reflect the individual cell voltages along with the overall pack voltage.


Appropriately, pressing the ‘balance’ button starts the process and a flashing symbol confirms the choice. The unit takes the lowest existing cell voltage as a benchmark from which to balance the pack until all cells are equal to within +/- 0.01V. Pressing ‘mode’ allows the lowest permitted voltage to be altered anywhere between 2.5 – 4.2V using the arrow keys. The unit will ‘balance’ during a charge so could be of use if an older charger without a built-in balancer function is being used.

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2-6 cell JST-XH ports live here on the side.


Battery Doctor will discharge a pack down (for long-term storage) to a default or pre-set voltage. Again flashing screen symbols alongside each cell voltage value confirm the selected operation. The default level is 3.9V which, of course, is a good setting for long term Li-Po storage. As you’d expect, a little heat can build up during this process but it’s pretty modest as the discharge rate is very gentle – I timed the discharge of a1300mAh 3S Li-Po battery at 2 ½ hours to get down to 3.9V.


This isn’t a function I’ve used a great deal as few of my electric powered models employ a separate receiver battery. The unit can measure the voltage between 1.2V and 8.5V from batteries fitted with a standard Futaba/JR plug. A separate power supply in the form of a JST plugged 2-3S Li-Po battery is required for the task and connects into the unit alongside the receiver battery. Handy? Hmm, yes up to a point. Flight-line practical? Perhaps less so given the need for a separate Li-Po battery to power the unit for the task.

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The receiver battery voltmeter aside, Battery Doctor is a handy little tool; The handy balance and discharge functions combined with the large screen and ease of operation means this is a widget that’ll see a lot of use on any dedicated electric flyers workbench or at the flying field.


Battery Doctor

Battery condition/measurement

Manufactured by
: Etronix

UK distributor:
CML Distribution Ltd
01527 575349


9 x 6 x 1.5 cm


• Measurable battery type and amount: Li-Po/Li-Fe 2-6 cell.
• Balance voltage setting range (lower limit): 2.0V – 3.9V (pre setting value 3.2V).
• Receiver battery voltage testing: 1.2V – 8.5V DC.

• Discharge voltage setting range (lower limit): 3.0V – 4.2V (pre-setting value 3.9V).


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