battery cape - is it working as expected?

Just got the chance today to run a set of batteries through my beagle bone with the battery cape installed. Run time while running off batteries with the DVI-D cape installed and a reasonably constant amount of heavey ethernet traffic running apt-get install / apt-get update extended to over 3 hours with a decent set of 4 costco/kirkland alkaline AA cells and was still sort of working when I threw away the batteries as dead. No, I’m not complaining as such but I’m wondering if it maybe should have run longer as the SRM for the battery cape states that it should supply 5V at 1A down to a value of 1.8V for 2 cells in series (VBAT). The board still best as I could tell was working up to the point that I pulled and trashed the batteries due to the ethernet no longer wanting to stay linked which a fresh set of batteries cured. The first set of the batteries now expended measured 1.25V per cell as opposed to 1.5V as new so I had 2.5V on VBAT when I finally called the batteries dead. Do I have an under performing boost converter on the cape, or is this about what I should expect from this cape design?