so I'm making a project, kind of BB-8 droid replica, and I stumbled upon a problem. Since I am using two RC brushless motors, ESC's and batteries, I want to make my Uno board fed up from those batteries. Also, I want to use inductive charging set that would charge both batteries. Can anyone tell me or give some kind of scheme how should I distribute the power from batteries and what additional boards should I buy?

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    – Nick Gammon
    Apr 27, 2016 at 22:02

1 Answer 1


The best option is to connect the 5V/2A output of the UBEC to the 5V pin on the Arduino. In my experience, 7.4V is not enough to feed into the input jack on an Arduino especially if it is from a battery, as the voltage will drop when current is being drawn by other loads. I have built an Arduino controlled robot using a 6V NiMH battery and brushed DC gearmotors (so no ESCs or UBEC) and used a $5 5V 1A step-up/step-down converter so that even if the battery voltage dropped below 5V, it could still power the board. However, since you have a UBEC that is not in use, use it. Note that if you put voltage into the 5V pin, disconnect it when you are connecting the arduino over USB or you might damage your board.

As for inductive charging, I don't know of any off-the-shelf solution designed for charging a 2S lithium ion battery. The best option for charging would probably be an easy way to open the ball to access the batteries.

  • About that problem You wrote in bold I had already known since I tried programming my ESC.
    – user20255
    Apr 27, 2016 at 18:26
  • EDIT I agree that opening and then charging would be the best choice but I'm making this as a gift and not much people have Li-ion chargers laying in their houses :D so the idea is to make it like Sphero BB-8 which is with inductive charging system. I found something in adafruits page adafruit.com/products/1407 which might work just fine because it would really fit into my project. The problem is that I would need a board that would take power from inductive set to charge the batteries... but any sketch I have made is messed up and I don't want to try anything that I don't get it.
    – user20255
    Apr 27, 2016 at 18:33
  • That inductive charging system is only capable of 5V at 500mA. You could easily step this up to charge a 6V or 7.2V NiMH battery as they are relatively forgiving about charging conditions, but it would probably be difficult (as well as dangerous) to try to charge a 2S LiPo this way.
    – 3871968
    Apr 27, 2016 at 18:38

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