The batteries in my sons iPhone 5C's had both started to fail.
The repair went almost exactly as demonstrated in the repair guide. The only things that were slightly different were these two items. First, the repair guide shows an peel-off strip that need to be exposed to attach the new adhesive to the end edge of the battery. The replacement strips didn't appear to have that on them, so I just folded the end over like the original strips were. Second, the replacement adhesive strip had the little hole on the opposite side from the ones that were already on the phone. After spending a few minutes trying to determine if this mattered or not, and trying to flip over the strips to put the hole on the same side as the original (that doesn't work), I concluded that it didn't matter, and put the strips on with the hole toward the center of the phone instead of on the side.
The original strips broke when I was trying to pull them out, and I didn't have the special heating bag that the repair guide uses. I did have both a gel-based and a clay-based commercial heating and cooling pads that my sons use for athletic injuries. The directions for heating on them worked just fine to heat up the adhesive on phones, and my plastic driver's license was the perfect replacement for the special plastic card that was used in the video as well.