Did the camera with AA cells for my sister's wedding recently. Just went and bought a 20 pack of Duracell AA cells, and used them for around 20 minutes in the camera, then turned it off, popped them out into the bag and put new ones in, so I could have 20 minutes of video on the camera in addition ( wanted a second view as well) to the main camera, and could move around with a small Canon to get closer up video. After signing changed them again, and did the reception shots and video as well same method. Only needed flash operation once the whole day, it was bright and sunny, and plenty of light even in the deepest shade under the lapa, and the wedding itself was done with a backdrop of the ocean.
Video camera battery was easy, had a few USB power banks around that were fully charged, and had tested before the camera would work properly with them attached and charging with camera operating. Did not need them though, 2 hours of onboard battery was more than enough.
Having Batterisers I would have had no warning of low battery ( I was changing out AA cells at half power indicated, not low, I wanted the confidence) till the camera stopped working during an image save, and this would have corrupted the flash card FAT table almost certainly. Camera FAT writes are power hungry, and there are critical points during writes that have the potential to lose all the data if power to the card or the processor dies.
Old batteries are not thrown out, I kept them separate, and am slowly using them up in the most common use of an AA cell, being remote controls ( where the 1A5 current peaks will cause issues with the Batteroo in some) and clocks. There they still last a few years before failure.