Electronic – Battery balancing circuit


I am facing the following problem. I need to power my device (RC airplane) with 2 separate battery packs 12 V each in order to extend the capacity. Connecting them in series will not work, as the power stage is not prepared for that. When I connect 2 battery packs in parallel, and there is a difference in their voltage, they will charge each other, thus a large current will flow making them explode even. I thought of a simple fix for that, it is visible in the below schematics:


simulate this circuit – Schematic created using CircuitLab

With those 2 diodes I loose some power as voltage drop, but there is no current flowing between the batteries.
What If I wanted to add a "voltage" balancing circuit in between them? Lets say if one battery is voltage is only 9 V, because its discharged a little bit, then the 12 V should charge it with set by me current, ie 2 A max. One could design a circuit for that but it would take some time and its not worth for this application I believe. Instead, I wonder either there are such IC's readily available? Bidirectional chargers of some sort? Could not find anything my self, but maybe I dont know how to name them?
I would appreciate all help regarding this problem.

Best Answer

You are much better off making ideal diodes using MOSFETs

enter image description here

  • Replaces a Power Schottky Diode
  • Internal 20mΩ N-Channel MOSFET
  • 0.5μs Turn-Off Time Limits Peak Fault Current
  • Operating Voltage Range: 9V to 26.5V
  • Smooth Switchover without Oscillation
  • No Reverse DC Current

But the simplest solution is a better Schottky Diode Array $6 with a heatsink enter image description here

These are common cathode. enter image description here

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