I did the same thing - was trying to get my flight controller configured and thought it would just sip power from the battery. But after 2 hours my servos suddenly stopped working and when I checked the battery, the cells were under 2V. I only had 2 charge cycles on the battery and luckily the charger still recognized it, so I immediately charged it at 1C back up to storage voltage and put it in the bag for the night. I am watching it carefully and it seems to charge a little slower than its twin. If it doesn't work out, it's only a $12 lesson-learned. Now when I work on my flight controller and need the battery plugged in for servo control, I keep the balance cable plugged into my charger so I can keep an eye on it.