A reader of our sibling publication Consumer Reports was concerned that his kids’ habit of running rechargeable batteries down almost to empty, then plugging them in and continuing to use them would damage the batteries somehow. No, our lab-coated colleagues responded: that’s not really bad for the batteries. What is bad for them is letting them drain all the way, then storing the item or the battery with no charge left. Charge them to 50% of capacity at least before letting them idle. Batteries lose their charge over time, and letting one get down to zero and then sit idle can do permanent damage.
Q&A: Is it OK use rechargeable batteries until they are almost run down? [Consumer Reports]