That's wierd, so do most of the rangefinders out there keep working but lose accuracy as the battery dies? I would have thought they would still be accurate untill they just couldn't get a reading. Has anybody else had this problem?

I am hoping to find a rangefinder under the Christmas tree this year and would like to know if I can have confidence in it all the time or if I'll have to change batteries every time one gets below half charge.

Maybe you need to have the rangefinder serviced, I just re-read your post and you said your battery was 1/2 to 3/4 full. I would think that there must be something else going on there.