How long will the batteries last? NMP Support Center December 14, 2011 21:39 The average overall life, based on normal use, is between 25 and 30 hours of operation. Related articles Would be possible to use the handheld sonar just for measuring distance/range of fish in front of the diver ? Live action use of the DT1H DepthTrax 1H Handheld Depth Finder Tech Tutorial I see a small amount of water leaking from near the activation button and display screen after submerging my Handheld Sonar. Is that normal? I tested my new Portable Sonar System at the YMCA pool and got wildly inaccurate measurements. At the 10-foot mark in the deep end, the said the water was 3.5, 4, 5 feet, but never 10. Comments 0 comments Please sign in to leave a comment.