From having designed stuff like this, a preassembled battery pack and a connector are much cheaper than AA battery connectors and the associated cabling. And it's very important to understand that these aren't AA batteries in the same sense that most people think of. (I'd recommend the OP stress this in their instructions.) Most people are familiar with alkaline batteries in the AA size. These are NiMH batteries, when most rechargable batteries in consumer electronics are Like Ion or Li Poly. Using the wrong batteries will most likely damage the electronics and/or explode the batteries. I'm sure the original designed thought they were providing a better experience than replacing batteries, but I don't understand the NiMH battery choice.

These batteries are fucking terrible. I rarely play with it and it’ll deplete a full charge in a month being idle.

My Nintendo controller lasts months of occisional usage

Thanks for sharing. Interesting that they didn't just use standard AA battery connecters. I guess they want you to buy a new controller after a few years.

Are the originals nimh not lithium?

So will we have to buy this new controller upgrade??

Thanks for sharing, creators like you feed the world

How long does the charge last on these batteries? I know it says 5 years but is that accurate?

Is there a similar tutorial for the 2015 controller available?

Thanks for confirming u/haxxa!

I used to look FCC images to confirm what batteries they were from this site.

https://fccid.io/VOB-P2920/Internal-Photos/TempConfidential-Internal-Photos-3107953

I'm glad someone popped one open and show the label of the battery.