I just finished 5 gigs with using Duracell 2000ma rechargable batteries which I got from B.J.'s wholesale ages ago .The batteries are about 2 to 3 years old.All the recordings run about almost 3
hours.Like said it could run up to 5 hours which they did at times.
I usually charge the batch the night before the gig.Then on the day of the gig I give them a booster charge hours before the show with my car AC inverter on the way to the show.I do the same with my Nikon digital camera batteries too.
I just picked up a new batch of Duracells a couple weeks ago with a charger at B.J.'s.
Digital brand batteries from Walmart were ok when new but they go bad when they get old quick.
Stay away from those fakes.