Thank you Ray and others for all the info on LiI batteries. They are new to me and I want to use and charge them correctly. My new Ridgid 12v drill/driver did not come with an owner's manual in the box and you might be able to help me with a charging question. At what stage in the charging procedure would you expect a defective battery to be recognized and the flashing lights to appear? On its first re-charge after first use, one of my 2 batteries went through the stages of evaluation and charging only to then, at the end of the appropriate charge, go back and flash "defective". I had thought the evaluation period would have turned up the "defect". What do you think might be happening? This "defective" battery has powered the driver just fine on a test; haven't used it on a job yet. Thanks.