In our lab we use LiPo batteries to power our quadrotors. Lately we have been experiencing stability issues when using certain batteries. The batteries seem to charge and balance normally and our battery monitor indicates they are fine even when putting them under load. However when we attempt to fly the quadrotor with one of these batteries, manually or autonomously, it has a severe tendency to pitch and/or roll. My guess is that the battery is not supplying sufficient power to all the motors which brings me to my question. Is this behavior indicative of a LiPo going bad? If so what is the best way to test a battery to confirm my suspicions?