My experience is that at around 20% the BP's performance becomes unreliable. That's when the level seems to fluctuate quite a lot, and right around the same time I can expect a request to replace the batteries. That advice really signifies it's too late,<smile> meaning that the unit will freeze up, my heart begin to pound wildly with fear, I rehearse what the repair process would be, etc. With dry mouth I unwrap the new batteries, insert them, reset what needs resetting, and happily, most joyously read away into the sunset. Dale -- Internal Virus Database is out-of-date. Checked by AVG Anti-Virus. Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005