Mini Voltsagger – RX Battery monitor for RC models

This is a small electronic project Vollrathd on RCGroups came up with a while back. All credit to this project should go to Vollrathd!

This little battery monitor can be quite handy for many pilots, even those who already have RX battery status via Telemetry as it will sample the battery status 5000 times per second and records the last minimum voltage found. Tests have shown that telemetry capable systems don’t always tell you the entire truth when showing the minimum voltage from the RX side, and it might even cause the loss of a model at some point..

With this little device you can be sure to know what the lowest value the RX pack went to during a flight.

NiMh pack connected up

The original RCGroup thread can be found at

The code here is just a slight modification to the original code from post #289 on the thread, which added support for and OLED screen. The revised code documents how to perform the calibration.

In order to build this little device, the following items are needed.

  • 1x Arduino Nano (both 3.3v and 5v version will work)
  • 1x OLED 128×64 display (4 pin version)
  • 1x 3.3K Ohm resistor
  • 2x 1K Ohm resister
  • 1x 47uF capacitor (ceramic or electrolyte)
  • 1 x 10uF capacitor (ceramic or electrolyte)

The device can be built by soldering the various parts directly to the Arduino Nano, but it will make it easier to use a PCB prototype board or the custom built PCB design that I’ve put together.

The PCB design will allow you to solder up the device without much effort. A small solder tip is required to solder the components as space can be a bit tight between the component.

My version of the schematic and PCB design can be found on my EasyEDA profile.

Schematics for use with OLED screen
Full layers
PCB Topside
PCB Underside
Components soldered onto the top side of the first prototype PCB.
LiFe pack connected up