Hey Craig, That's exactly what the good people over at Garrett told me. One bar / four bars / same performance ! From a personal standpoint (and considering my limited knowledge of metal detecting), I really can't tell the difference, nor can I argue the point either way. However, I believe there are many that disagree with that theory, and change the batteries immediately, when that first bar drops off. Personally, I usually wait for the second bar to drop, not because I experience a drop in performance, but just because of the question in my mind.
So, am I missing something here? Are you saying that this is true (1 bar / 4 bar/ same performance), only with rechargeable batteries, or is this true with batteries in general ? I understand about the way rechargeables drop off quickly vs more of a linear drop with alkaline.....