DC Fan wrote in post #14230543
Writing as an owner of a Canon 60D and a user of a battery grip for that camera: the grip has a battery tray that uses six
AA batteries. From using this equipment, it's clear that battery life with six NiMH AA's in a 60D is as long, if not longer, than with two of the camera's LP-E6 batteries.
The 60D was used extensively during the basketball season: it was easy to have a set of rechargeable AA's last for several basketball games in the camera.
Also as an owner of a 60D with grips, and having other EOS bodies, also gripped, using 6 AA batteries will not last *nearly* as long as two LP-E6 batteries. Indeed, if that's what you're seeing, it would seem that either your grip or more likely the batteries are defective (or at least v cheap 3rd party batteries).
Rechargeable AAs are usually around 2500mAh @ 1.2V (so 6x these are 2500mAh @ 7.2V). The canon batteries are 1800mAh @ 7.4V *each*. So it's evident that two of these are going to last longer, as extensive real world testing should (and does) show.
Hope that helps!