We all know we shouldn't discharge a Lipo Cell under 3V.
In order to monitor pack voltage I built this simple monitor using some spare parts I had at home.
The overall weight is 4grams, and power consumption is 2mA with no LEDs on.
The first LED (Green) lights up 10.5V, the second at 10V, the third (Red) at 9.5V and the last one at 9V.
You can build it over a universal printed circuit board or use my innovative solid state technique (Intel already asked for the patent...) that can be seen in my gallery.
Now the Disclaimer:
You are on your own. I take no responsibility of any sort regarding the usefulness, appropriateness or safety of the monitor.
It you are not an experienced electronics technician, call your buddy or stay away. A short circuit in the monitor could put your Lipo pack on fire!
It's easy to find an excuse to do wrong. Hard is not to find an excuse to do right.