I stand corrected. Thanks.
What's the mAh rating of the rechargeables you use?
Flintstone
edit:
Looking around this forum, I found a report of 2 hours using cheap Radio Shack batteries, and 4+ hours using 2500mAh rechargeables. Elsewhere on the web, reviewers generally report 4+ hours. Tascam says 5.5 hours with alkaline AAs, but that may be with phantom power turned off.
Because the R-4 uses a hard disc rather than flash memory like the HD-P2, it gets shorter life from its 8 AA batteries.