This is a very good point. If it's as easy to replace as AA and it lasts longer, it's just better all around.

A few problems: it will still use rare earth metals, and those are a hot political topic right now with China restricting them

The fact that AAs are eternal. Who knows if this specific battery will still be available in 10 years.

Also, the small problem of you can't just buy a new one at Walmart. It is small, but out of sight, out of mind, and out of the public consciousness.

Problems with Li-ion itself, I suppose. What we really need is a standardized small rectangle form factor since Li-ion is just more efficient in that shape.

Kinda like an Xbox controller, except that the rechargeable battery was actually included instead of being a separate purchase, and no adapter is needed for either battery types.

I don’t recall the Xbox rechargeable battery pack requiring an adapter. It just pops in where the AAs would be.

I had something similar to this for the original fat gameboy in the 90s, except instead of being a rechargeable battery, which weren’t really worth it then, it was a plug-in adapter, and it replaced the battery cover panel to do so.

I genuinely don’t understand why that sort of thing doesn’t exist anymore, either as plug adapters or as rechargeable bricks (or both, why not), so you can fall back on standard AA or AAA if necessary. They’d be standardized parts so manufacturers would only get the original sale but.. so? Would it not also be just easier from a manufacturer standpoint?

People forget we had hot-swappable li-ion batteries decades ago in phones and DSLRs. They absolutely could’ve done that with no to minimal form-factor changes.

18650 is awesome, a good balance of weight to capacity. They are the standard cells used in laptops, vapes, small powerbanks, power tool batteries, and so on. They can also go into a fairly standard charger for AA and AAA batteries and give a lovely nominal 3.7V.

That said, pouches are better for inside a device like a controller. The weight of a battery is significantly influenced by the casing. A pouch is almost entirely capacity, a cell like an 18650 or AA is largely the metal of the casing. If you have the pouch inside the plastic of the device you can save that weight.

I think you might be onto something. Probably the reason why they went for a built-in battery is space limitations

Nowadays you can get AA-shaped lithium cells. Anyways I hope free battery is easy to replace after 2 years.

Low self discharge NiMH batteries work great.

and the batteries are widely available and reasonably priced

If they're not a standard battery design, then they will not be widely available or reasonably priced.

Yeah the issue is easily replaceable standardized sized battery, if li-ion started doing that, I'd be all in Li-ion band wagon for handheld consumer electronics, till that point I must agree with OP and i would keep demanding Aa batteries and use my niMH cells

If it's not a standard battery design, then being able to replace it doesn't matter as much. It would mean the company can charge excessive fees because their 'custom' battery is the only one that's compatible with their product.