So I use 4 600EXs for all my lighting needs, powered by Sanyo eneloops. In the past using 580s and 430s, I've used a full power flash dump and counted in seconds for the ready beep to determine roughly how juiced a set of batteries were - 2.5s meant fine, 3.5s-4s served as a reminder to change out a set for a fresh.
What I've been finding with the 600EXs is that even when the batteries are near death, the ready beep still engages after 2.5s-3s after a 1/1 test, only to discover it stops firing and dies just a few pops later mid session.
I doubled checked to ensure every test on each flash is not set to 1/32 but to 1/1 full power. It's frustrating when you think everything is charged and a speedlite fails, and perhaps I've been foolishly relying on those ready beeps to gauge battery status.
Anyone else experiencing this?