Having no electronic expertise, I can offer no technical explanation. What I can share is a seemingly inconsequential niggle with the GB Pro's battery indicator and/or the Energizers I been using. It is inconsistent. I have noticed this since my first battery (factory installed). After 5 or 6 hours of constant usage, the indicator can wiggle from 1 to 2 to 3 bars, then back down to 2 bars and then rise up to 3 bars and stay there at 3 bars for another 4 or 5 hrs usage (on the next hunt).
I have an LG cell phone that exhibits similar behavior...it can read 3 bars (full charge), but I know after 2 days of usage, it should be showing 1 bar max. No, it shows 3 bars, and when I plug it in to charge, the indicator shows it charging from one or ZERO bars. Anyways back to the GB Pro; I said to myself, "Dammit, this thing's bat indicator is like my phone's!" So if it says 1 bar, the battery MAY be very close to being drained.
Hope you guys don't encounter this little prob. I can live with it and really must get rechargeable batteries.