I was recently checking the health of old M600 batteries (TB48S) we don't use anymore for jobs. I ran into a set of batteries that hadn't be used in over a year and a half, and saw the battery mAh capacity increase from its previous capacity losses, around 3770, to 5700 as if it was a brand new battery. This happened in 5 out of the 6 batteries in the set. Has this happened to anyone else? Does anyone know what might be the reasoning behind this?