I hadn't had to put a concrete anchor in for 4 months until I wrote about it yesterday, and then of course I had to put 24 in today. Used my customer's SDS-MAX M18 drill and two 9.0Ah batteries to put in that many 1/2" x 4" anchors. I think the one battery must be weak; 1/2" anchors are pretty puny compared to what we usually install with that drill.