measuring lipo voltage

Hi

I have a 11.1v lipo battery powering my robot and it happened once that the voltage dropped under 3v per cell. In order to avoid this happening again, i want to see the battery level trough the arduino. Maybe I can do this connecting one of the cells directly in one analog pin and gnd and then multiply by 3 (i can use a jst-xh plug).
-Am i right?
-Is there a better way?

http://www.ebay.com/itm/3S-12V-Li-ion-Li-Po-Lithium-Battery-18650-Charger-Discharge-Protection-Board-/331319407053?hash=item4d242cf1cd

Boardburner's suggestion of a battery protection circuit is always a good idea. Prevents overcharge, undercharge, and overcurrent.

If you want to measure the voltage with the Arduino, then it's time to learn Voltage Dividers - SparkFun Learn. R1 of 47K and R2 of 22K would be a good choice.